Merged PR 1202: Vehicle Service System v1.2.0.0

## New Features

### Shared Memory DataStore

* Replaced the existing in-memory DataStore with a shared-memory implementation using Windows File Mapping.
* Added support for sharing application data between multiple running instances.
* Created separate mappings for users, notifications, services, bookings, invoices, payments, and other entities.

### Binary Data Storage

* Added binary serialization for all major entities.
* Introduced record tracking to handle new, modified, and deleted records.
* Added automatic growth and shrinking of mappings when required.

## Refactoring

### DataStore Changes

* Refactored DataStore to use shared memory instead of local process memory.
* Added generic helper functions for loading and saving records.
* Updated application startup and shutdown to initialize and clean up shared-memory resources.

### Synchronization

* Added a global mutex to synchronize datastore operations across processes.
* Added remapping logic to detect mapping size changes made by other instances.

## Bug Fixes

* Fixed issues with data not being shared correctly between multiple application instances.
* Improved reliability of record updates and deletions.
* Fixed stale mapping issues when mappings were resized by another process.

Related work items: #1925, #1926, #1927, #1928, #1929, #1930, #1949, #1950, #1951, #1952, #1953, #1954, #1955, #1956, #1957, #1958, #1959, #1960, #2061, #2074, #2075, #2076, #2077, #2078, #2079, #2080, #2081, #2082, #2100, #2105, #2114, #2115, #2116

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem.vcxproj

@@ -102,7 +102,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>_DEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalIncludeDirectories>$(ProjectDir)models;$(ProjectDir)controllers;$(ProjectDir)factories;$(ProjectDir)views;$(ProjectDir)services;$(ProjectDir)utilities;$(ProjectDir)core\patterns;$(ProjectDir)datastores;$(ProjectDir)datastores\sharedmemory;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>$(ProjectDir)models;$(ProjectDir)controllers;$(ProjectDir)factories;$(ProjectDir)views;$(ProjectDir)services;$(ProjectDir)utilities;$(ProjectDir)core\patterns;$(ProjectDir)datastores;$(ProjectDir)core\sharedmemory;$(ProjectDir)core\events;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
@@ -117,7 +117,7 @@
       <SDLCheck>true</SDLCheck>
       <PreprocessorDefinitions>NDEBUG;_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <ConformanceMode>true</ConformanceMode>
-      <AdditionalIncludeDirectories>$(ProjectDir)models;$(ProjectDir)controllers;$(ProjectDir)factories;$(ProjectDir)views;$(ProjectDir)services;$(ProjectDir)utilities;$(ProjectDir)core\patterns;$(ProjectDir)datastores;$(ProjectDir)datastores\sharedmemory;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>$(ProjectDir)models;$(ProjectDir)controllers;$(ProjectDir)factories;$(ProjectDir)views;$(ProjectDir)services;$(ProjectDir)utilities;$(ProjectDir)core\patterns;$(ProjectDir)datastores;$(ProjectDir)core\sharedmemory;$(ProjectDir)core\events;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
@@ -126,10 +126,11 @@
   </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="controllers\Controller.cpp" />
+    <ClCompile Include="core\events\EventManager.cpp" />
     <ClCompile Include="core\patterns\Observer.cpp" />
     <ClCompile Include="core\patterns\Subject.cpp" />
+    <ClCompile Include="core\sharedmemory\SharedMemory.cpp" />
     <ClCompile Include="datastores\DataStore.cpp" />
-    <ClCompile Include="datastores\sharedmemory\SharedMemory.cpp" />
     <ClCompile Include="models\ComboPackage.cpp" />
     <ClCompile Include="models\InventoryItem.cpp" />
     <ClCompile Include="models\Invoice.cpp" />
@@ -148,21 +149,23 @@
     <ClCompile Include="utilities\Validator.cpp" />
     <ClCompile Include="views\AdminMenu.cpp" />
     <ClCompile Include="views\CustomerMenu.cpp" />
+    <ClCompile Include="views\Menu.cpp" />
     <ClCompile Include="views\TechnicianMenu.cpp" />
     <ClCompile Include="views\UserInterface.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="controllers\Controller.h" />
+    <ClInclude Include="core\events\EventManager.h" />
     <ClInclude Include="core\patterns\Observer.h" />
     <ClInclude Include="core\patterns\Subject.h" />
+    <ClInclude Include="core\sharedmemory\FileHeader.h" />
+    <ClInclude Include="core\sharedmemory\MappingInfo.h" />
+    <ClInclude Include="core\sharedmemory\RecordState.h" />
+    <ClInclude Include="core\sharedmemory\SerializedRecords.h" />
+    <ClInclude Include="core\sharedmemory\SharedMemory.h" />
+    <ClInclude Include="core\sharedmemory\TrackedRecord.h" />
     <ClInclude Include="datastores\DataStore.h" />
     <ClInclude Include="datastores\DataStoreLockGuard.h" />
-    <ClInclude Include="datastores\sharedmemory\FileHeader.h" />
-    <ClInclude Include="datastores\sharedmemory\MappingInfo.h" />
-    <ClInclude Include="datastores\sharedmemory\RecordState.h" />
-    <ClInclude Include="datastores\sharedmemory\SerializedRecords.h" />
-    <ClInclude Include="datastores\sharedmemory\SharedMemory.h" />
-    <ClInclude Include="datastores\sharedmemory\TrackedRecord.h" />
     <ClInclude Include="factories\Factory.h" />
     <ClInclude Include="models\ComboPackage.h" />
     <ClInclude Include="models\InventoryItem.h" />
@@ -191,6 +194,7 @@
     <ClInclude Include="utilities\Vector.h" />
     <ClInclude Include="views\AdminMenu.h" />
     <ClInclude Include="views\CustomerMenu.h" />
+    <ClInclude Include="views\Menu.h" />
     <ClInclude Include="views\MenuHelper.h" />
     <ClInclude Include="views\TechnicianMenu.h" />
     <ClInclude Include="views\UserInterface.h" />

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem.vcxproj.filters

@@ -64,11 +64,17 @@
     <Filter Include="Source Files\Core\Patterns">
       <UniqueIdentifier>{8057b93d-51a9-42df-b06e-01ce395f6308}</UniqueIdentifier>
     </Filter>
-    <Filter Include="Header Files\DataStores\SharedMemory">
-      <UniqueIdentifier>{ec639004-44c6-4bd6-9963-077adde82b5f}</UniqueIdentifier>
+    <Filter Include="Header Files\Core\SharedMemory">
+      <UniqueIdentifier>{d9da9793-fe6f-4914-bee3-99d5934da228}</UniqueIdentifier>
     </Filter>
-    <Filter Include="Source Files\DataStores\SharedMemory">
-      <UniqueIdentifier>{7aa8722e-adfa-466e-8211-de63f3b7892b}</UniqueIdentifier>
+    <Filter Include="Source Files\Core\SharedMemory">
+      <UniqueIdentifier>{0769afb6-f57d-4ae3-a1cf-ceca6e606af0}</UniqueIdentifier>
+    </Filter>
+    <Filter Include="Header Files\Core\Events">
+      <UniqueIdentifier>{85029bdb-6941-41dc-a3a7-9e5841671d8c}</UniqueIdentifier>
+    </Filter>
+    <Filter Include="Source Files\Core\Events">
+      <UniqueIdentifier>{1050aca7-6f2c-4ccb-a446-db9c898c3599}</UniqueIdentifier>
     </Filter>
   </ItemGroup>
   <ItemGroup>
@@ -144,8 +150,14 @@
     <ClCompile Include="models\ComboPackage.cpp">
       <Filter>Source Files\Models</Filter>
     </ClCompile>
-    <ClCompile Include="datastores\sharedmemory\SharedMemory.cpp">
-      <Filter>Source Files\DataStores\SharedMemory</Filter>
+    <ClCompile Include="core\sharedmemory\SharedMemory.cpp">
+      <Filter>Source Files\Core\SharedMemory</Filter>
+    </ClCompile>
+    <ClCompile Include="core\events\EventManager.cpp">
+      <Filter>Source Files\Core\Events</Filter>
+    </ClCompile>
+    <ClCompile Include="views\Menu.cpp">
+      <Filter>Source Files\Views</Filter>
     </ClCompile>
   </ItemGroup>
   <ItemGroup>
@@ -254,26 +266,32 @@
     <ClInclude Include="views\MenuHelper.h">
       <Filter>Header Files\Views</Filter>
     </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\FileHeader.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\MappingInfo.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\RecordState.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\TrackedRecord.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\SerializedRecords.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
-    <ClInclude Include="datastores\sharedmemory\SharedMemory.h">
-      <Filter>Header Files\DataStores\SharedMemory</Filter>
-    </ClInclude>
     <ClInclude Include="datastores\DataStoreLockGuard.h">
       <Filter>Header Files\DataStores</Filter>
     </ClInclude>
+    <ClInclude Include="core\sharedmemory\FileHeader.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\sharedmemory\MappingInfo.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\sharedmemory\RecordState.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\sharedmemory\SerializedRecords.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\sharedmemory\SharedMemory.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\sharedmemory\TrackedRecord.h">
+      <Filter>Header Files\Core\SharedMemory</Filter>
+    </ClInclude>
+    <ClInclude Include="core\events\EventManager.h">
+      <Filter>Header Files\Core\Events</Filter>
+    </ClInclude>
+    <ClInclude Include="views\Menu.h">
+      <Filter>Header Files\Views</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/controllers/Controller.cpp

@@ -234,6 +234,17 @@ void Controller::removeInventoryItem(const std::string& inventoryItemID)
     m_inventoryManagementService.removeInventoryItem(inventoryItemID);
 }
 
+/*
+Function: removeServiceBooking
+Description: Removes a service booking from the service management system by its booking ID.
+Parameter: const std::string& bookingID - ID of the service booking
+Return type: void
+*/
+void Controller::removeServiceBooking(const std::string& bookingID)
+{
+    m_serviceManagementService.removeServiceBooking(bookingID);
+}
+
 /*
 Function: addInventoryItemStock
 Description: Adds stock to an existing inventory item in the inventory management service.
@@ -265,6 +276,7 @@ util::Map<std::string, const ServiceBooking*> Controller::getServiceBookings()
     return readOnlyServiceBookings;
 }
 
+
 /*
 Function: getServiceBookingsByUser
 Description: Retrieves all service bookings for a specific user.
@@ -622,3 +634,16 @@ void Controller::shutdown()
     auto& dataStore = DataStore::getInstance();
     dataStore.shutdown();
 }
+
+/*
+Function: registerEvents
+Description: Registers menu event handles with the authentication
+             service.
+Parameter: HANDLE accountDisabledEvent - account disabled event handle
+           HANDLE notificationAvailableEvent - notification event handle
+Return type: void
+*/
+void Controller::registerEvents(HANDLE accountDisabledEvent, HANDLE notificationAvailableEvent)
+{
+    m_authenticationManagementService.registerEvents(accountDisabledEvent, notificationAvailableEvent);
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/controllers/Controller.h

@@ -8,6 +8,7 @@ Date:19-May-2026
 */
 
 #pragma once
+#include <windows.h>
 #include <string>
 #include "AuthenticationManagementService.h"
 #include "Enums.h"
@@ -57,6 +58,7 @@ public:
     util::Map<std::string, const User*> getUsers(util::UserType userType);
     void createJobCard(const std::string& bookingID, const std::string& technicianID, const std::string& serviceID);
     void createService(const std::string& name, const util::Vector<std::string>& inventoryItemIDs, double laborCost);
+    void removeServiceBooking(const std::string& bookingID);
     void removeService(const std::string& serviceID);
     util::Map<std::string, const JobCard*> getJobCardsByUser();
     void updateJobStatus(const std::string& jobID);
@@ -72,4 +74,5 @@ public:
     void configureNotifications(bool paymentNotifications, bool serviceNotifications);
     bool initialize();
     void shutdown();
+    void registerEvents(HANDLE accountDisabledEvent, HANDLE notificationAvailableEvent);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/core/events/EventManager.cpp

@@ -0,0 +1,225 @@
+/*
+File: EventManager.cpp
+Description: Implementation file containing the method definitions of the
+             EventManager class, including listener management and
+             interprocess event publishing.
+Author: Trenser
+Date:15-Jun-2026
+*/
+
+#include <iostream>
+#include <stdexcept>
+#include "EventManager.h"
+
+namespace
+{
+    const std::string USER_DISABLED_EVENT = "userDisabled_";
+
+    const std::string NOTIFICATION_AVAILABLE_EVENT = "notificationAvailable_";
+}
+
+/*
+Function: EventManager
+Description: Constructs an EventManager instance with default values.
+Parameter: None
+Return type: None
+*/
+EventManager::EventManager()
+    :
+    m_userDisabledEvent(NULL),
+    m_notificationAvailableEvent(NULL),
+    m_shutdownEvent(NULL),
+    m_running(false) {}
+
+/*
+Function: ~EventManager
+Description: Destroys the EventManager and performs final cleanup.
+Parameter: None
+Return type: None
+*/
+EventManager::~EventManager()
+{
+    shutdown();
+    if (m_listenerThread.joinable())
+    {
+        m_listenerThread.join();
+    }
+}
+
+/*
+Function: initialize
+Description: Creates the user-specific events and starts the listener
+             thread.
+Parameter: const std::string& userId - unique identifier of the user
+           std::function<void()> userDisabledCallback - callback for
+           user disable events
+           std::function<void()> notificationCallback - callback for
+           notification events
+Return type: bool - true if initialization succeeds, false otherwise
+*/
+bool EventManager::initialize(const std::string& userId, std::function<void()> userDisabledCallback, std::function<void()> notificationCallback)
+{
+    if (m_running.load())
+    {
+        return false;
+    }
+    m_userDisabledCallback = userDisabledCallback;
+    m_notificationCallback = notificationCallback;
+    m_userDisabledEvent = CreateEventA(NULL, FALSE, FALSE, (USER_DISABLED_EVENT + userId).c_str());
+    if (!m_userDisabledEvent)
+    {
+        return false;
+    }
+    if (GetLastError() == ERROR_ALREADY_EXISTS)
+    {
+        CloseHandle(m_userDisabledEvent);
+        m_userDisabledEvent = NULL;
+        throw std::runtime_error("Only one session allowed per user.");
+    }
+    m_notificationAvailableEvent = CreateEventA(NULL, FALSE, FALSE, (NOTIFICATION_AVAILABLE_EVENT + userId).c_str());
+    if (!m_notificationAvailableEvent)
+    {
+        CloseHandle(m_userDisabledEvent);
+        m_userDisabledEvent = NULL;
+        return false;
+    }
+    m_shutdownEvent = CreateEventA(NULL, FALSE, FALSE, NULL);
+    if (!m_shutdownEvent)
+    {
+        CloseHandle(m_userDisabledEvent);
+        CloseHandle(m_notificationAvailableEvent);
+        m_userDisabledEvent = NULL;
+        m_notificationAvailableEvent = NULL;
+        return false;
+    }
+    m_running.store(true);
+    m_listenerThread = std::thread(&EventManager::run, this);
+    return true;
+}
+
+/*
+Function: shutdown
+Description: Stops the listener thread and releases event resources.
+Parameter: None
+Return type: None
+*/
+void EventManager::shutdown()
+{
+    if (!m_running.load())
+    {
+        return;
+    }
+    m_running.store(false);
+    if (m_shutdownEvent)
+    {
+        SetEvent(m_shutdownEvent);
+    }
+    if (m_listenerThread.joinable())
+    {
+        if (std::this_thread::get_id() != m_listenerThread.get_id())
+        {
+            m_listenerThread.join();
+        }
+    }
+    if (m_userDisabledEvent)
+    {
+        CloseHandle(m_userDisabledEvent);
+        m_userDisabledEvent = NULL;
+    }
+    if (m_notificationAvailableEvent)
+    {
+        CloseHandle(m_notificationAvailableEvent);
+        m_notificationAvailableEvent = NULL;
+    }
+    if (m_shutdownEvent)
+    {
+        CloseHandle(m_shutdownEvent);
+        m_shutdownEvent = NULL;
+    }
+}
+
+/*
+Function: run
+Description: Waits for and dispatches user-related events.
+Parameter: None
+Return type: void
+*/
+void EventManager::run()
+{
+    HANDLE handles[3];
+    handles[0] = m_userDisabledEvent;
+    handles[1] = m_notificationAvailableEvent;
+    handles[2] = m_shutdownEvent;
+    while (m_running.load())
+    {
+        DWORD result = WaitForMultipleObjects(3, handles, FALSE, INFINITE);
+        switch (result)
+        {
+        case WAIT_OBJECT_0:
+            try
+            {
+                if (m_userDisabledCallback)
+                {
+                    m_userDisabledCallback();
+                }
+            }
+            catch (const std::exception& exception)
+            {
+                std::cout << exception.what() << std::endl;
+            }
+            break;
+        case WAIT_OBJECT_0 + 1:
+            try
+            {
+                if (m_notificationCallback)
+                {
+                    m_notificationCallback();
+                }
+            }
+            catch (const std::exception& exception)
+            {
+                std::cout << exception.what() << std::endl;
+            }
+            break;
+        case WAIT_OBJECT_0 + 2:
+            return;
+        default:
+            break;
+        }
+    }
+}
+
+/*
+Function: sendUserDisabledEvent
+Description: Publishes a user disabled event for a specific user.
+Parameter: const std::string& userId - target user identifier
+Return type: void
+*/
+void EventManager::sendUserDisabledEvent(const std::string& userId)
+{
+    HANDLE eventHandle = CreateEventA(NULL, FALSE, FALSE, (USER_DISABLED_EVENT + userId).c_str());
+    if (!eventHandle)
+    {
+        return;
+    }
+    SetEvent(eventHandle);
+    CloseHandle(eventHandle);
+}
+
+/*
+Function: sendNotificationAvailableEvent
+Description: Publishes a notification available event for a specific
+             user.
+Parameter: const std::string& userId - target user identifier
+Return type: void
+*/
+void EventManager::sendNotificationAvailableEvent(const std::string& userId)
+{
+    HANDLE eventHandle = CreateEventA(NULL, FALSE, FALSE, (NOTIFICATION_AVAILABLE_EVENT + userId).c_str());
+    if (!eventHandle)
+    {
+        return;
+    }
+    SetEvent(eventHandle);
+    CloseHandle(eventHandle);
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/core/events/EventManager.h

@@ -0,0 +1,37 @@
+/*
+File: EventManager.h
+Description: Header file declaring the EventManager class, which manages
+             user-specific interprocess events for user disable and
+             notification availability updates.
+Author: Trenser
+Date:15-Jun-2026
+*/
+
+#pragma once
+
+#include <windows.h>
+#include <atomic>
+#include <functional>
+#include <string>
+#include <thread>
+
+class EventManager
+{
+private:
+    HANDLE m_userDisabledEvent;
+    HANDLE m_notificationAvailableEvent;
+    HANDLE m_shutdownEvent;
+    std::atomic<bool> m_running;
+    std::thread m_listenerThread;
+    std::function<void()> m_userDisabledCallback;
+    std::function<void()> m_notificationCallback;
+    void run();
+
+public:
+    EventManager();
+    ~EventManager();
+    bool initialize(const std::string& userId, std::function<void()> userDisabledCallback, std::function<void()> notificationCallback);
+    void shutdown();
+    static void sendUserDisabledEvent(const std::string& userId);
+    static void sendNotificationAvailableEvent(const std::string& userId);
+};

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/datastores/DataStore.cpp

@@ -12,6 +12,9 @@ Date: 19-May-2026
 #include "Config.h"
 #include "SerializedRecords.h"
 #include "FileHelper.h"
+#include "ServiceBooking.h"
+#include "JobCard.h"
+#include "Invoice.h"
 
 /*
 Function: DataStore
@@ -252,6 +255,28 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<Service>>& DataStore::getServices()
 {
+    util::Map<std::string, TrackedRecord<Service>> services = loadRecords<Service, SerializedService>(m_services);
+    refreshCache(m_serviceCache, services);
+    util::Map<std::string, TrackedRecord<InventoryItem>>& inventoryItems = getInventoryItems();
+    size_t numberOfServices = m_serviceCache.getSize();
+    for (int iteratorOne =0; iteratorOne < numberOfServices; iteratorOne++)
+    {
+        Service* currentService = m_serviceCache.getValueAt(iteratorOne).data;
+        util::Map<std::string, InventoryItem*> inventoryItemMap;
+        util::Vector<std::string> currentServiceInventoryItem = currentService->getRequiredInventoryItemIDs();
+        for (int iteratorTwo = 0; iteratorTwo < currentServiceInventoryItem.getSize(); iteratorTwo++)
+        {
+            const std::string& currentInventoryItemId = currentServiceInventoryItem[iteratorTwo];
+            int currentInventoryItemIndex = inventoryItems.find(currentInventoryItemId);
+            if (currentInventoryItemIndex == -1)
+            {
+                throw std::runtime_error("Invalid inventory item ID");
+            }
+            InventoryItem* currentItem = inventoryItems.getValueAt(currentInventoryItemIndex).data;
+            inventoryItemMap[currentInventoryItemId] = currentItem;
+        }
+        currentService->setRequiredInventoryItems(inventoryItemMap);
+    }
     return m_serviceCache;
 }
 
@@ -265,6 +290,28 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<ComboPackage>>& DataStore::getComboPackages()
 {
+    util::Map<std::string, TrackedRecord<ComboPackage>> comboPackages = loadRecords<ComboPackage, SerializedComboPackage>(m_comboPackages);
+    refreshCache(m_comboPackageCache, comboPackages);
+    util::Map<std::string, TrackedRecord<Service>>& services = getServices();
+    size_t numberOfComboPackages = m_comboPackageCache.getSize();
+    for (int iteratorOne = 0; iteratorOne < numberOfComboPackages; iteratorOne++)
+    {
+        ComboPackage* currentComboPackage =  m_comboPackageCache.getValueAt(iteratorOne).data;
+        util::Vector<std::string> currentServiceIds = currentComboPackage->getServiceIDs();
+        util::Map<std::string, Service*> currentComboPackageServices;
+        for (int iteratorTwo = 0; iteratorTwo < currentServiceIds.getSize(); iteratorTwo++)
+        {
+            const std::string& currentServiceId = currentServiceIds[iteratorTwo];
+            int serviceIndex = services.find(currentServiceId);
+            if (serviceIndex == -1)
+            {
+                throw std::runtime_error("Invalid service ID");
+            }
+            Service* currentService = services.getValueAt(serviceIndex).data;
+            currentComboPackageServices[currentServiceId] = currentService;
+        }
+        currentComboPackage->setServices(currentComboPackageServices);
+    }
     return m_comboPackageCache;
 }
 
@@ -278,6 +325,8 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<InventoryItem>>& DataStore::getInventoryItems()
 {
+    auto inventoryItems = loadRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems);
+    refreshCache(m_inventoryItemCache, inventoryItems);
     return m_inventoryItemCache;
 }
 
@@ -291,6 +340,49 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<ServiceBooking>>& DataStore::getServiceBookings()
 {
+    util::Map<std::string, TrackedRecord<ServiceBooking>> serviceBookings = loadRecords<ServiceBooking, SerializedServiceBooking>(m_serviceBookings);
+    refreshCache(m_serviceBookingCache, serviceBookings);
+    auto& users = getUsers();
+    auto& services = getServices();
+    size_t numberOfServiceBookings = m_serviceBookingCache.getSize();
+    for (int iteratorOne = 0; iteratorOne < numberOfServiceBookings; iteratorOne++)
+    {
+        ServiceBooking* serviceBooking = m_serviceBookingCache.getValueAt(iteratorOne).data;
+        auto& serviceIds = serviceBooking->getServiceIDs();
+        util::Map<std::string, Service*> servicesInBooking;
+        for (int iteratorTwo = 0; iteratorTwo < serviceIds.getSize(); iteratorTwo++)
+        {
+            const std::string& currentServiceId = serviceIds[iteratorTwo];
+            int serviceIndex = services.find(currentServiceId);
+            if (serviceIndex == -1)
+            {
+                throw std::runtime_error("Invalid service index.");
+            }
+            auto& currentService = services.getValueAt(serviceIndex);
+            servicesInBooking[currentServiceId] = currentService.data;
+        }
+        serviceBooking->setServices(servicesInBooking);
+        if (!serviceBooking->getCustomerId().empty())
+        {
+            int userIndex = users.find(serviceBooking->getCustomerId());
+            if (userIndex == -1)
+            {
+                throw std::runtime_error("Invalid user index.");
+            }
+            auto& customer = users.getValueAt(userIndex);
+            serviceBooking->setCustomer(customer.data);
+        }
+        if (!serviceBooking->getAssignedTechnicianId().empty())
+        {
+            int technicianIndex = users.find(serviceBooking->getAssignedTechnicianId());
+            if (technicianIndex == -1)
+            {
+                throw std::runtime_error("Invalid technician index.");
+            }
+            auto& technician = users.getValueAt(technicianIndex);
+            serviceBooking->setAssignedTechnician(technician.data);
+        }
+    }
     return m_serviceBookingCache;
 }
 
@@ -304,9 +396,51 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<JobCard>>& DataStore::getJobCards()
 {
+    util::Map<std::string, TrackedRecord<JobCard>> jobCards = loadRecords<JobCard, SerializedJobCard>(m_jobCards);
+    refreshCache(m_jobCardCache, jobCards);
+    auto& serviceBookings = getServiceBookings();
+    auto& services = getServices();
+    auto& users = getUsers();
+    int numberOfJobCards = m_jobCardCache.getSize();
+    for (int iterator = 0; iterator < numberOfJobCards; iterator++)
+    {
+        JobCard* jobCard = m_jobCardCache.getValueAt(iterator).data;
+        if (!jobCard)
+        {
+            continue;
+        }
+        const std::string& bookingId = jobCard->getBookingId();
+        int bookingIndex = serviceBookings.find(bookingId);
+        if (bookingIndex == -1)
+        {
+            throw std::runtime_error("Invalid booking ID: " + bookingId);
+        }
+        auto& trackedBooking = serviceBookings.getValueAt(bookingIndex);
+        jobCard->setBooking(trackedBooking.data);
+        const std::string& serviceId = jobCard->getServiceId();
+        int serviceIndex = services.find(serviceId);
+        if (serviceIndex == -1)
+        {
+            throw std::runtime_error("Invalid service ID: " + serviceId);
+        }
+        auto& trackedService = services.getValueAt(serviceIndex);
+        jobCard->setService(trackedService.data);
+        const std::string& technicianId = jobCard->getTechnicianId();
+        if (!technicianId.empty())
+        {
+            int technicianIndex = users.find(technicianId);
+            if (technicianIndex == -1)
+            {
+                throw std::runtime_error("Invalid technician ID: " + technicianId);
+            }
+            auto& trackedTechnician = users.getValueAt(technicianIndex);
+            jobCard->setTechnician(trackedTechnician.data);
+        }
+    }
     return m_jobCardCache;
 }
 
+
 /*
 Function: getInvoices
 Description: Retrieves all invoice records from the datastore.
@@ -317,6 +451,45 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<Invoice>>& DataStore::getInvoices()
 {
+    auto& serviceBookings = getServiceBookings();
+    auto& inventoryItems = getInventoryItems();
+    util::Map<std::string, TrackedRecord<Invoice>> invoices = loadRecords<Invoice, SerializedInvoice>(m_invoices);
+    refreshCache(m_invoiceCache, invoices);
+    for (int iterator = 0; iterator < m_invoiceCache.getSize(); iterator++)
+    {
+        auto& trackedInvoice = m_invoiceCache.getValueAt(iterator);
+        Invoice* invoice = trackedInvoice.data;
+        if (!invoice)
+        {
+            continue;
+        }
+        const std::string& currentBookingId = invoice->getBookingId();
+        int currentBookingIndex = serviceBookings.find(currentBookingId);
+        if (currentBookingIndex == -1)
+        {
+            throw std::runtime_error("Invalid Service Booking Index.");
+        }
+        ServiceBooking* currentBooking = serviceBookings.getValueAt(currentBookingIndex).data;
+        auto& currentInventoryItemIds = invoice->getPartIDs();
+        util::Map<std::string, InventoryItem*> currentInventoryItems;
+        for (int iterator = 0; iterator < currentInventoryItemIds.getSize(); iterator++)
+        {
+            const std::string& currentItemId = currentInventoryItemIds[iterator];
+            int currentItemIndex = inventoryItems.find(currentItemId);
+            if (currentItemIndex == -1)
+            {
+                throw std::runtime_error("Invalid Inventory item id.");
+            }
+            InventoryItem* currentItem = inventoryItems.getValueAt(currentItemIndex).data;
+            if (!currentItem)
+            {
+                continue;
+            }
+            currentInventoryItems[currentItemId] = currentItem;
+        }
+        invoice->setBooking(currentBooking);
+        invoice->setParts(currentInventoryItems);
+    }
     return m_invoiceCache;
 }
 
@@ -426,6 +599,7 @@ Returns:
 */
 void DataStore::saveServices()
 {
+    saveRecords<Service, SerializedService>(m_services, m_serviceCache);
 }
 
 /*
@@ -438,6 +612,7 @@ Returns:
 */
 void DataStore::saveComboPackages()
 {
+    saveRecords<ComboPackage, SerializedComboPackage>(m_comboPackages, m_comboPackageCache);
 }
 
 /*
@@ -450,6 +625,7 @@ Returns:
 */
 void DataStore::saveInventoryItems()
 {
+    saveRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems, m_inventoryItemCache);
 }
 
 /*
@@ -462,6 +638,7 @@ Returns:
 */
 void DataStore::saveServiceBookings()
 {
+    saveRecords<ServiceBooking, SerializedServiceBooking>(m_serviceBookings, m_serviceBookingCache);
 }
 
 /*
@@ -474,6 +651,7 @@ Returns:
 */
 void DataStore::saveJobCards()
 {
+    saveRecords<JobCard, SerializedJobCard>(m_jobCards, m_jobCardCache);
 }
 
 /*
@@ -486,6 +664,7 @@ Returns:
 */
 void DataStore::saveInvoices()
 {
+    saveRecords<Invoice, SerializedInvoice>(m_invoices, m_invoiceCache);
 }
 
 /*
@@ -512,7 +691,7 @@ void DataStore::saveObservers(MappingInfo& mapping, util::Map<std::string, User*
     SharedMemory::setRecordCount(mapping, observerCount);
     for (size_t index = 0; index < observerCount; index++)
     {
-        SerializedObserver serializedObserver;
+        SerializedObserver serializedObserver{};
         User* user = observers.getValueAt(static_cast<int>(index));
         strcpy_s(serializedObserver.id, sizeof(serializedObserver.id), user->getId().c_str());
         SerializedObserver* destination = static_cast<SerializedObserver*>(SharedMemory::getRecordAddress(mapping, index));
@@ -601,5 +780,4 @@ bool DataStore::unlockDataStore()
         return false;
     }
     return ReleaseMutex(m_globalMutex) != 0;
-}
-
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/datastores/DataStore.h

@@ -11,6 +11,7 @@ Date: 19-May-2026
 #include "Map.h"
 #include "MappingInfo.h"
 #include "TrackedRecord.h"
+#include "SerializedRecords.h"
 #include "SharedMemory.h"
 #include "User.h"
 #include "Notification.h"
@@ -219,6 +220,12 @@ void DataStore::refreshCache(util::Map<std::string, TrackedRecord<TObject>>& cac
         if (oldIndex != -1)
         {
             TrackedRecord<TObject>& oldRecord = oldCache.getValueAt(oldIndex);
+            if (oldRecord.state == RecordState::MODIFIED)
+            {
+                delete refreshedRecord.data;
+                cache.insert(id, oldRecord);
+                continue;
+            }
             *oldRecord.data = *refreshedRecord.data;
             oldRecord.slotIndex = refreshedRecord.slotIndex;
             oldRecord.state = refreshedRecord.state;

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/ComboPackage.cpp

@@ -9,6 +9,7 @@ Date: 19-May-2026
 
 #include <sstream>
 #include <stdexcept>
+#include "SerializedRecords.h"
 #include "ComboPackage.h"
 #include "Service.h"
 #include "Factory.h"
@@ -28,7 +29,8 @@ Returns:
 ComboPackage::ComboPackage()
     : m_id("CMP" + std::to_string(++m_uid)),
     m_status(util::State::ACTIVE),
-    m_discountPercentage(0.0) {}
+    m_discountPercentage(0.0) {
+}
 
 /*
 Function: ComboPackage
@@ -270,72 +272,38 @@ static util::Vector<std::string> getServiceIDsAsVector(const std::string& servic
 
 /*
 Function: serialize
-Description: Serializes the combo package into a CSV-formatted string.
+Description: Serializes the ComboPackage object into a SerializedComboPackage record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized combo package record
+    - SerializedComboPackage: Serialized representation of the combo package
 */
-std::string ComboPackage::serialize() const
+SerializedComboPackage ComboPackage::serialize() const
 {
-    std::ostringstream serializedComboPackage;
-    serializedComboPackage << m_id << ','
-        << m_packageName << ','
-        << m_discountPercentage << ','
-        << getServiceIDsAsString(m_serviceIDs) << ','
-        << util::getStateString(m_status);
-    return serializedComboPackage.str();
+    SerializedComboPackage serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.packageName, sizeof(serialized.packageName), m_packageName.c_str());
+    strcpy_s(serialized.serviceIDs, sizeof(serialized.serviceIDs), getServiceIDsAsString(m_serviceIDs).c_str());
+    serialized.discountPercentage = m_discountPercentage;
+    serialized.status = m_status;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into a ComboPackage object.
+Description: Deserializes a SerializedComboPackage record into a ComboPackage object.
 Parameters:
-    - record: const std::string&, serialized combo package record
+    - serializedComboPackage: const SerializedComboPackage&, serialized combo package record
 Returns:
     - ComboPackage*: Pointer to the deserialized ComboPackage object
-Throws:
-    - std::runtime_error if data is invalid
 */
-ComboPackage* ComboPackage::deserialize(const std::string& record)
+ComboPackage* ComboPackage::deserialize(const SerializedComboPackage& serializedComboPackage)
 {
-    std::string id, packageName;
-    std::string discountPercentageString, serviceIDsString, statusString;
-    double discountPercentage;
-    std::istringstream serializedComboPackage(record);
-    getline(serializedComboPackage, id, ',');
-    getline(serializedComboPackage, packageName, ',');
-    getline(serializedComboPackage, discountPercentageString, ',');
-    getline(serializedComboPackage, serviceIDsString, ',');
-    getline(serializedComboPackage, statusString, ',');
-    try
-    {
-        discountPercentage = std::stod(discountPercentageString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid combo package data");
-    }
-    util::Vector<std::string> serviceIDs = getServiceIDsAsVector(serviceIDsString);
-    util::State status = util::getState(statusString);
+    util::Vector<std::string> serviceIDs = getServiceIDsAsVector(serializedComboPackage.serviceIDs);
     return Factory::getObject<ComboPackage>(
-        id,
-        packageName,
-        discountPercentage,
+        serializedComboPackage.id,
+        serializedComboPackage.packageName,
+        serializedComboPackage.discountPercentage,
         serviceIDs,
-        status
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for combo package serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,PackageName,DiscountPercentage,ServiceIDs,Status")
-*/
-std::string ComboPackage::getHeaders()
-{
-    return "ID,PackageName,DiscountPercentage,ServiceIDs,Status";
-}
+        serializedComboPackage.status);
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/ComboPackage.h

@@ -39,7 +39,6 @@ public:
     void setDiscountPercentage(double discountPercentage);
     void setServices(const util::Map<std::string, Service*>& services);
     void setState(util::State status);
-    std::string serialize() const;
-    static ComboPackage* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedComboPackage serialize() const;
+    static ComboPackage* deserialize(const SerializedComboPackage&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/InventoryItem.cpp

@@ -8,6 +8,7 @@ Date: 19-May-2026
 
 #include <sstream>
 #include <stdexcept>
+#include "SerializedRecords.h"
 #include "Factory.h"
 #include "StringHelper.h"
 #include "InventoryItem.h"
@@ -27,7 +28,8 @@ InventoryItem::InventoryItem()
     : m_id("IIM" + std::to_string(++m_uid)),
     m_quantity(0),
     m_status(util::State::ACTIVE),
-    m_price(0.0) {}
+    m_price(0.0) {
+}
 
 /*
 Function: InventoryItem
@@ -45,7 +47,8 @@ InventoryItem::InventoryItem(const std::string& partName, int quantity, double p
     m_partName(partName),
     m_quantity(quantity),
     m_status(util::State::ACTIVE),
-    m_price(price) {}
+    m_price(price) {
+}
 
 /*
 Function: InventoryItem (parameterized constructor with ID)
@@ -206,73 +209,37 @@ void InventoryItem::setState(util::State status)
 
 /*
 Function: serialize
-Description: Serializes the inventory item into a CSV-formatted string.
+Description: Serializes the InventoryItem object into a SerializedInventoryItem record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized inventory item record
+    - SerializedInventoryItem: Serialized representation of the inventory item
 */
-std::string InventoryItem::serialize() const
+SerializedInventoryItem InventoryItem::serialize() const
 {
-    std::ostringstream serializedInventoryItem;
-    serializedInventoryItem << m_id << ','
-        << m_partName << ','
-        << m_quantity << ','
-        << m_price << ','
-        << util::getStateString(m_status);
-    return serializedInventoryItem.str();
+    SerializedInventoryItem serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.partName, sizeof(serialized.partName), m_partName.c_str());
+    serialized.quantity = m_quantity;
+    serialized.price = m_price;
+    serialized.status = m_status;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into an InventoryItem object.
+Description: Deserializes a SerializedInventoryItem record into an InventoryItem object.
 Parameters:
-    - record: const std::string&, serialized inventory item record
+    - serializedInventoryItem: const SerializedInventoryItem&, serialized inventory item record
 Returns:
     - InventoryItem*: Pointer to the deserialized InventoryItem object
-Throws:
-    - std::runtime_error if data is invalid
 */
-InventoryItem* InventoryItem::deserialize(const std::string& record)
+InventoryItem* InventoryItem::deserialize(const SerializedInventoryItem& serializedInventoryItem)
 {
-    std::string id, partName;
-    std::string quantityString, priceString, statusString;
-    int quantity;
-    double price;
-    std::istringstream serializedInventoryItem(record);
-    getline(serializedInventoryItem, id, ',');
-    getline(serializedInventoryItem, partName, ',');
-    getline(serializedInventoryItem, quantityString, ',');
-    getline(serializedInventoryItem, priceString, ',');
-    getline(serializedInventoryItem, statusString, ',');
-    try
-    {
-        quantity = std::stoi(quantityString);
-        price = std::stod(priceString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid inventory item data");
-    }
-    util::State status = util::getState(statusString);
     return Factory::getObject<InventoryItem>(
-        id,
-        partName,
-        quantity,
-        price,
-        status
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for inventory item serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,PartName,Quantity,Price,Status")
-*/
-std::string InventoryItem::getHeaders()
-{
-    return "ID,PartName,Quantity,Price,Status";
+        serializedInventoryItem.id,
+        serializedInventoryItem.partName,
+        serializedInventoryItem.quantity,
+        serializedInventoryItem.price,
+        serializedInventoryItem.status);
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/InventoryItem.h

@@ -6,11 +6,12 @@ Author: Trenser
 Date: 19-May-2026
 */
 
-
 #pragma once
 #include <string>
 #include "Enums.h"
 
+struct SerializedInventoryItem;
+
 class InventoryItem
 {
 private:
@@ -34,7 +35,6 @@ public:
     void setQuantity(int quantity);
     void setPrice(double price);
     void setState(util::State status);
-    std::string serialize() const;
-    static InventoryItem* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedInventoryItem serialize() const;
+    static InventoryItem* deserialize(const SerializedInventoryItem&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/Invoice.cpp

@@ -9,6 +9,7 @@ Date: 19-May-2026
 
 #include <sstream>
 #include <stdexcept>
+#include "SerializedRecords.h"
 #include "Invoice.h"
 #include "Factory.h"
 #include "InventoryItem.h"
@@ -34,7 +35,8 @@ Invoice::Invoice()
     m_discountPercentage(0.0),
     m_totalAmount(0.0),
     m_paymentMethod(util::PaymentMode()),
-    m_status(util::PaymentStatus()) {}
+    m_status(util::PaymentStatus()) {
+}
 
 /*
 Function: Invoice
@@ -57,16 +59,16 @@ Returns:
 Invoice::Invoice(
     const std::string& bookingId,
     ServiceBooking* booking,
-    const util::Timestamp& invoiceDate, 
-    double laborCost, 
+    const util::Timestamp& invoiceDate,
+    double laborCost,
     const util::Map<std::string, InventoryItem*>& parts,
     double partsCost,
-    double discountPercentage, 
-    double totalAmount, 
-    const util::Timestamp& paymentDate, 
-    util::PaymentMode paymentMethod, 
+    double discountPercentage,
+    double totalAmount,
+    const util::Timestamp& paymentDate,
+    util::PaymentMode paymentMethod,
     util::PaymentStatus status
-    )
+)
     : m_id("INV" + std::to_string(++m_uid)),
     m_bookingId(bookingId),
     m_booking(booking),
@@ -78,7 +80,7 @@ Invoice::Invoice(
     m_totalAmount(totalAmount),
     m_paymentDate(paymentDate),
     m_paymentMethod(paymentMethod),
-    m_status(status) 
+    m_status(status)
 {
     int numberOfParts = m_parts.getSize();
     auto partPointers = m_parts.getValues();
@@ -473,100 +475,50 @@ static util::Vector<std::string> getPartIDsAsVector(const std::string& partIDsSt
 
 /*
 Function: serialize
-Description: Serializes the invoice into a CSV-formatted string.
+Description: Serializes the Invoice object into a SerializedInvoice record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized invoice record
+    - SerializedInvoice: Serialized representation of the invoice
 */
-std::string Invoice::serialize() const
+SerializedInvoice Invoice::serialize() const
 {
-    std::ostringstream serializedInvoice;
-    serializedInvoice << m_id << ','
-        << m_bookingId << ','
-        << m_invoiceDate.toString() << ','
-        << m_laborCost << ','
-        << getPartIDsAsString(m_partIDs) << ','
-        << m_partsCost << ','
-        << m_discountPercentage << ','
-        << m_totalAmount << ','
-        << m_paymentDate.toString() << ','
-        << util::getPaymentModeString(m_paymentMethod) << ','
-        << util::getPaymentStatusString(m_status);
-    return serializedInvoice.str();
+    SerializedInvoice serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.bookingId, sizeof(serialized.bookingId), m_bookingId.c_str());
+    strcpy_s(serialized.partIDs, sizeof(serialized.partIDs), getPartIDsAsString(m_partIDs).c_str());
+    serialized.invoiceDate = m_invoiceDate;
+    serialized.laborCost = m_laborCost;
+    serialized.partsCost = m_partsCost;
+    serialized.discountPercentage = m_discountPercentage;
+    serialized.totalAmount = m_totalAmount;
+    serialized.paymentDate = m_paymentDate;
+    serialized.paymentMethod = m_paymentMethod;
+    serialized.status = m_status;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into an Invoice object.
+Description: Deserializes a SerializedInvoice record into an Invoice object.
 Parameters:
-    - record: const std::string&, serialized invoice record
+    - serializedInvoice: const SerializedInvoice&, serialized invoice record
 Returns:
     - Invoice*: Pointer to the deserialized Invoice object
-Throws:
-    - std::runtime_error if data is invalid
 */
-Invoice* Invoice::deserialize(const std::string& record)
+Invoice* Invoice::deserialize(const SerializedInvoice& serializedInvoice)
 {
-    std::string id, bookingId;
-    std::string invoiceDateString, laborCostString, partIDsString;
-    std::string partsCostString, discountPercentageString, totalAmountString;
-    std::string paymentDateString, paymentMethodString, statusString;
-    double laborCost, partsCost, discountPercentage, totalAmount;
-    std::istringstream serializedInvoice(record);
-    getline(serializedInvoice, id, ',');
-    getline(serializedInvoice, bookingId, ',');
-    getline(serializedInvoice, invoiceDateString, ',');
-    getline(serializedInvoice, laborCostString, ',');
-    getline(serializedInvoice, partIDsString, ',');
-    getline(serializedInvoice, partsCostString, ',');
-    getline(serializedInvoice, discountPercentageString, ',');
-    getline(serializedInvoice, totalAmountString, ',');
-    getline(serializedInvoice, paymentDateString, ',');
-    getline(serializedInvoice, paymentMethodString, ',');
-    getline(serializedInvoice, statusString, ',');
-    util::Timestamp invoiceDate;
-    util::Timestamp paymentDate;
-    try
-    {
-        invoiceDate = util::Timestamp::fromString(invoiceDateString);
-        paymentDate = util::Timestamp::fromString(paymentDateString);
-        laborCost = std::stod(laborCostString);
-        partsCost = std::stod(partsCostString);
-        discountPercentage = std::stod(discountPercentageString);
-        totalAmount = std::stod(totalAmountString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid invoice data");
-    }
-    util::Vector<std::string> partIDs = getPartIDsAsVector(partIDsString);
-    util::PaymentMode paymentMethod = util::getPaymentMode(paymentMethodString);
-    util::PaymentStatus status = util::getPaymentStatus(statusString);
+    util::Vector<std::string> partIDs = getPartIDsAsVector(serializedInvoice.partIDs);
     return Factory::getObject<Invoice>(
-        id,
-        bookingId,
-        invoiceDate,
+        serializedInvoice.id,
+        serializedInvoice.bookingId,
+        serializedInvoice.invoiceDate,
         partIDs,
-        laborCost,
-        partsCost,
-        discountPercentage,
-        totalAmount,
-        paymentDate,
-        paymentMethod,
-        status
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for invoice serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,BookingID,InvoiceDate,LaborCost,PartIDs,PartsCost,DiscountPercentage,TotalAmount,PaymentDate,PaymentMethod,Status")
-*/
-std::string Invoice::getHeaders()
-{
-    return "ID,BookingID,InvoiceDate,LaborCost,PartIDs,PartsCost,DiscountPercentage,TotalAmount,PaymentDate,PaymentMethod,Status";
+        serializedInvoice.laborCost,
+        serializedInvoice.partsCost,
+        serializedInvoice.discountPercentage,
+        serializedInvoice.totalAmount,
+        serializedInvoice.paymentDate,
+        serializedInvoice.paymentMethod,
+        serializedInvoice.status);
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/Invoice.h

@@ -6,7 +6,6 @@ Author: Trenser
 Date: 19-May-2026
 */
 
-
 #pragma once
 #include <string>
 #include "Map.h"
@@ -16,6 +15,7 @@ Date: 19-May-2026
 
 class ServiceBooking;
 class InventoryItem;
+struct SerializedInvoice;
 
 class Invoice
 {
@@ -39,14 +39,14 @@ public:
     Invoice(
         const std::string& bookingId,
         ServiceBooking* booking,
-        const util::Timestamp& invoiceDate, 
-        double laborCost, 
-        const util::Map<std::string,InventoryItem*>& parts,
+        const util::Timestamp& invoiceDate,
+        double laborCost,
+        const util::Map<std::string, InventoryItem*>& parts,
         double partsCost,
-        double discountPercentage, 
-        double totalAmount, 
-        const util::Timestamp& paymentDate, 
-        util::PaymentMode paymentMethod, 
+        double discountPercentage,
+        double totalAmount,
+        const util::Timestamp& paymentDate,
+        util::PaymentMode paymentMethod,
         util::PaymentStatus status
     );
     Invoice(
@@ -87,7 +87,6 @@ public:
     void setPaymentDate(const util::Timestamp& paymentDate);
     void setPaymentMethod(util::PaymentMode paymentMethod);
     void setStatus(util::PaymentStatus status);
-    std::string serialize() const;
-    static Invoice* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedInvoice serialize() const;
+    static Invoice* deserialize(const SerializedInvoice&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/JobCard.cpp

@@ -9,6 +9,7 @@ Date:19-May-2026
 
 #include <sstream>
 #include <stdexcept>
+#include "SerializedRecords.h"
 #include "JobCard.h"
 #include "Factory.h"
 #include "StringHelper.h"
@@ -28,7 +29,8 @@ JobCard::JobCard()
     m_booking(nullptr),
     m_service(nullptr),
     m_technician(nullptr),
-    m_status(util::ServiceJobStatus()) {}
+    m_status(util::ServiceJobStatus()) {
+}
 
 /*
 Function: JobCard
@@ -65,7 +67,8 @@ JobCard::JobCard(const std::string& bookingId,
     m_technician(technician),
     m_assignedDate(assignedDate),
     m_status(status),
-    m_completionDate(completionDate) {}
+    m_completionDate(completionDate) {
+}
 
 /*
 Function: JobCard (parameterized constructor with ID)
@@ -351,79 +354,41 @@ void JobCard::setCompletionDate(const util::Timestamp& completionDate)
 
 /*
 Function: serialize
-Description: Serializes the job card into a CSV-formatted string.
+Description: Serializes the JobCard object into a SerializedJobCard record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized job card record
+    - SerializedJobCard: Serialized representation of the job card
 */
-std::string JobCard::serialize() const
+SerializedJobCard JobCard::serialize() const
 {
-    std::ostringstream serializedJobCard;
-    serializedJobCard << m_id << ','
-        << m_bookingId << ','
-        << m_serviceId << ','
-        << m_technicianId << ','
-        << m_assignedDate.toString() << ','
-        << util::getServiceJobStatusString(m_status) << ','
-        << m_completionDate.toString();
-    return serializedJobCard.str();
+    SerializedJobCard serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.bookingId, sizeof(serialized.bookingId), m_bookingId.c_str());
+    strcpy_s(serialized.serviceId, sizeof(serialized.serviceId), m_serviceId.c_str());
+    strcpy_s(serialized.technicianId, sizeof(serialized.technicianId), m_technicianId.c_str());
+    serialized.assignedDate = m_assignedDate;
+    serialized.status = m_status;
+    serialized.completionDate = m_completionDate;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into a JobCard object.
+Description: Deserializes a SerializedJobCard record into a JobCard object.
 Parameters:
-    - record: const std::string&, serialized job card record
+    - serializedJobCard: const SerializedJobCard&, serialized job card record
 Returns:
     - JobCard*: Pointer to the deserialized JobCard object
-Throws:
-    - std::runtime_error if timestamp parsing fails
 */
-JobCard* JobCard::deserialize(const std::string& record)
+JobCard* JobCard::deserialize(const SerializedJobCard& serializedJobCard)
 {
-    std::string id, bookingId, serviceId, technicianId;
-    std::string assignedDateString, statusString, completionDateString;
-    std::istringstream serializedJobCard(record);
-    getline(serializedJobCard, id, ',');
-    getline(serializedJobCard, bookingId, ',');
-    getline(serializedJobCard, serviceId, ',');
-    getline(serializedJobCard, technicianId, ',');
-    getline(serializedJobCard, assignedDateString, ',');
-    getline(serializedJobCard, statusString, ',');
-    getline(serializedJobCard, completionDateString, ',');
-    util::Timestamp assignedDate;
-    util::Timestamp completionDate;
-    try
-    {
-        assignedDate = util::Timestamp::fromString(assignedDateString);
-        completionDate = util::Timestamp::fromString(completionDateString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid timestamp");
-    }
-    util::ServiceJobStatus status = util::getServiceJobStatus(statusString);
     return Factory::getObject<JobCard>(
-        id,
-        bookingId,
-        serviceId,
-        technicianId,
-        assignedDate,
-        status,
-        completionDate
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for job card serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,BookingID,ServiceID,TechnicianID,AssignedDate,Status,CompletionDate")
-*/
-std::string JobCard::getHeaders()
-{
-    return "ID,BookingID,ServiceID,TechnicianID,AssignedDate,Status,CompletionDate";
+        serializedJobCard.id,
+        serializedJobCard.bookingId,
+        serializedJobCard.serviceId,
+        serializedJobCard.technicianId,
+        serializedJobCard.assignedDate,
+        serializedJobCard.status,
+        serializedJobCard.completionDate);
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/JobCard.h

@@ -15,6 +15,7 @@ Date:19-May-2026
 class ServiceBooking;
 class Service;
 class User;
+struct SerializedJobCard;
 
 class JobCard
 {
@@ -34,11 +35,11 @@ public:
     JobCard();
     JobCard(const std::string& bookingId,
         ServiceBooking* booking,
-        Service* service, 
-        const std::string& serviceId, 
-        const std::string& technicianId, 
-        User* technician, 
-        const util::Timestamp& assignedDate, 
+        Service* service,
+        const std::string& serviceId,
+        const std::string& technicianId,
+        User* technician,
+        const util::Timestamp& assignedDate,
         util::ServiceJobStatus status,
         const util::Timestamp& completionDate
     );
@@ -70,7 +71,6 @@ public:
     void setAssignedDate(const util::Timestamp& assignedDate);
     void setStatus(util::ServiceJobStatus status);
     void setCompletionDate(const util::Timestamp& completionDate);
-    std::string serialize() const;
-    static JobCard* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedJobCard serialize() const;
+    static JobCard* deserialize(const SerializedJobCard&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/Service.cpp

@@ -8,6 +8,7 @@ Date: 19-May-2026
 */
 
 #include <sstream>
+#include "SerializedRecords.h"
 #include "Service.h"
 #include "InventoryItem.h"
 #include "StringHelper.h"
@@ -27,7 +28,8 @@ Returns:
 Service::Service()
     : m_id("SRV" + std::to_string(++m_uid)),
     m_status(util::State::ACTIVE),
-    m_laborCost(0.0) {}
+    m_laborCost(0.0) {
+}
 
 /*
 Function: Service
@@ -44,7 +46,7 @@ Service::Service(const std::string& name, const util::Map<std::string, Inventory
     m_name(name),
     m_requiredInventoryItems(requiredInventoryItems),
     m_status(util::State::ACTIVE),
-    m_laborCost(laborCost) 
+    m_laborCost(laborCost)
 {
     int numberOfInventoryItems = m_requiredInventoryItems.getSize();
     auto inventoryItemPointers = m_requiredInventoryItems.getValues();
@@ -266,72 +268,38 @@ static util::Vector<std::string> getInventoryItemIDsAsVector(const std::string&
 
 /*
 Function: serialize
-Description: Serializes the service into a CSV-formatted string.
+Description: Serializes the Service object into a SerializedService record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized service record
+    - SerializedService: Serialized representation of the service
 */
-std::string Service::serialize() const
+SerializedService Service::serialize() const
 {
-    std::ostringstream serializedService;
-    serializedService << m_id << ','
-        << m_name << ','
-        << getInventoryItemIDsAsString(m_requiredInventoryItemIDs) << ','
-        << m_laborCost << ','
-        << util::getStateString(m_status);
-    return serializedService.str();
+    SerializedService serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.name, sizeof(serialized.name), m_name.c_str());
+    strcpy_s(serialized.inventoryItemIDs, sizeof(serialized.inventoryItemIDs), getInventoryItemIDsAsString(m_requiredInventoryItemIDs).c_str());
+    serialized.laborCost = m_laborCost;
+    serialized.status = m_status;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into a Service object.
+Description: Deserializes a SerializedService record into a Service object.
 Parameters:
-    - record: const std::string&, serialized service record
+    - serializedService: const SerializedService&, serialized service record
 Returns:
     - Service*: Pointer to the deserialized Service object
-Throws:
-    - std::runtime_error if labor cost parsing fails
 */
-Service* Service::deserialize(const std::string& record)
+Service* Service::deserialize(const SerializedService& serializedService)
 {
-    std::string id, name;
-    std::string inventoryItemIDsString, laborCostString, statusString;
-    double laborCost;
-    std::istringstream serializedService(record);
-    getline(serializedService, id, ',');
-    getline(serializedService, name, ',');
-    getline(serializedService, inventoryItemIDsString, ',');
-    getline(serializedService, laborCostString, ',');
-    getline(serializedService, statusString, ',');
-    util::Vector<std::string> inventoryItemIDs = getInventoryItemIDsAsVector(inventoryItemIDsString);
-    try
-    {
-        laborCost = std::stod(laborCostString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid labor cost");
-    }
-    util::State status = util::getState(statusString);
+    util::Vector<std::string> inventoryItemIDs = getInventoryItemIDsAsVector(serializedService.inventoryItemIDs);
     return Factory::getObject<Service>(
-        id,
-        name,
+        serializedService.id,
+        serializedService.name,
         inventoryItemIDs,
-        laborCost,
-        status
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for service serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,Name,InventoryIDs,LaborCost,Status")
-*/
-std::string Service::getHeaders()
-{
-    return "ID,Name,InventoryIDs,LaborCost,Status";
+        serializedService.laborCost,
+        serializedService.status);
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/Service.h

@@ -6,7 +6,6 @@ Author: Trenser
 Date: 19-May-2026
 */
 
-
 #pragma once
 #include <string>
 #include "Map.h"
@@ -14,6 +13,7 @@ Date: 19-May-2026
 #include "Enums.h"
 
 class InventoryItem;
+struct SerializedService;
 
 class Service
 {
@@ -40,7 +40,6 @@ public:
     void setRequiredInventoryItems(const util::Map<std::string, InventoryItem*>& requiredInventoryItems);
     void setLaborCost(double laborCost);
     void setState(util::State status);
-    std::string serialize() const;
-    static Service* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedService serialize() const;
+    static Service* deserialize(const SerializedService&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/ServiceBooking.cpp

@@ -6,8 +6,10 @@ Description: Implementation file containing the method definitions of the
 Author: Trenser
 Date:19-May-2026
 */
+
 #include <stdexcept>
 #include <sstream>
+#include "SerializedRecords.h"
 #include "ServiceBooking.h"
 #include "Service.h"
 #include "Enums.h"
@@ -28,7 +30,8 @@ ServiceBooking::ServiceBooking()
     m_customer(nullptr),
     m_assignedTechnician(nullptr),
     m_status(util::ServiceJobStatus::PENDING),
-    m_discountPercentage(0.0) {}
+    m_discountPercentage(0.0) {
+}
 
 /*
 Function: ServiceBooking
@@ -437,84 +440,46 @@ static util::Vector<std::string> getServiceIDsAsVector(const std::string& servic
 
 /*
 Function: serialize
-Description: Serializes the service booking into a CSV-formatted string.
+Description: Serializes the ServiceBooking object into a SerializedServiceBooking record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized booking record
+    - SerializedServiceBooking: Serialized representation of the service booking
 */
-std::string ServiceBooking::serialize() const
+SerializedServiceBooking ServiceBooking::serialize() const
 {
-    std::ostringstream serializedBooking;
-    serializedBooking << m_id << ','
-        << util::getServiceJobStatusString(m_status) << ','
-        << getServiceIDsAsString(m_serviceIDs) << ','
-        << m_customerId << ','
-        << m_vehicleNumber << ','
-        << m_vehicleBrand << ','
-        << m_vehicleModel << ','
-        << m_assignedTechnicianId << ','
-        << m_discountPercentage << ',';
-    return serializedBooking.str();
+    SerializedServiceBooking serialized = {};
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    strcpy_s(serialized.serviceIDs, sizeof(serialized.serviceIDs), getServiceIDsAsString(m_serviceIDs).c_str());
+    strcpy_s(serialized.customerId, sizeof(serialized.customerId), m_customerId.c_str());
+    strcpy_s(serialized.vehicleNumber, sizeof(serialized.vehicleNumber), m_vehicleNumber.c_str());
+    strcpy_s(serialized.vehicleBrand, sizeof(serialized.vehicleBrand), m_vehicleBrand.c_str());
+    strcpy_s(serialized.vehicleModel, sizeof(serialized.vehicleModel), m_vehicleModel.c_str());
+    strcpy_s(serialized.assignedTechnicianId, sizeof(serialized.assignedTechnicianId), m_assignedTechnicianId.c_str());
+    serialized.status = m_status;
+    serialized.discountPercentage = m_discountPercentage;
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into a ServiceBooking object.
+Description: Deserializes a SerializedServiceBooking record into a ServiceBooking object.
 Parameters:
-    - record: const std::string&, serialized booking record
+    - serializedServiceBooking: const SerializedServiceBooking&, serialized service booking record
 Returns:
     - ServiceBooking*: Pointer to the deserialized ServiceBooking object
-Throws:
-    - std::runtime_error if discount percentage parsing fails
 */
-ServiceBooking* ServiceBooking::deserialize(const std::string& record)
+ServiceBooking* ServiceBooking::deserialize(const SerializedServiceBooking& serializedServiceBooking)
 {
-    std::string id, customerId, vehicleNumber, vehicleBrand, vehicleModel, assignedTechnicianId;
-    std::string serviceJobStatusString, serviceIDsString, discountPercentageString;
-    double discountPercentage;
-    std::istringstream serializedBooking(record);
-    getline(serializedBooking, id, ',');
-    getline(serializedBooking, serviceJobStatusString, ',');
-    getline(serializedBooking, serviceIDsString, ',');
-    getline(serializedBooking, customerId, ',');
-    getline(serializedBooking, vehicleNumber, ',');
-    getline(serializedBooking, vehicleBrand, ',');
-    getline(serializedBooking, vehicleModel, ',');
-    getline(serializedBooking, assignedTechnicianId, ',');
-    getline(serializedBooking, discountPercentageString, ',');
-    util::Vector<std::string> serviceIDs = getServiceIDsAsVector(serviceIDsString);
-    try
-    {
-        discountPercentage = std::stod(discountPercentageString);
-    }
-    catch (...)
-    {
-        throw std::runtime_error("Invalid discount percentage");
-    }
-    util::ServiceJobStatus status = util::getServiceJobStatus(serviceJobStatusString);
+    util::Vector<std::string> serviceIDs = getServiceIDsAsVector(serializedServiceBooking.serviceIDs);
     return Factory::getObject<ServiceBooking>(
-        id,
-        status,
+        serializedServiceBooking.id,
+        serializedServiceBooking.status,
         serviceIDs,
-        customerId,
-        vehicleNumber,
-        vehicleBrand,
-        vehicleModel,
-        assignedTechnicianId,
-        discountPercentage
-    );
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for service booking serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,Status,ServiceIDs,CustomerID,VehicleNumber,VehicleBrand,VehicleModel,AssignedTechnicianID,DiscountPercentage")
-*/
-std::string ServiceBooking::getHeaders()
-{
-    return "ID,Status,ServiceIDs,CustomerID,VehicleNumber,VehicleBrand,VehicleModel,AssignedTechnicianID,DiscountPercentage";
+        serializedServiceBooking.customerId,
+        serializedServiceBooking.vehicleNumber,
+        serializedServiceBooking.vehicleBrand,
+        serializedServiceBooking.vehicleModel,
+        serializedServiceBooking.assignedTechnicianId,
+        serializedServiceBooking.discountPercentage);
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/ServiceBooking.h

@@ -6,6 +6,7 @@ Description: Header file declaring the ServiceBooking class, which represents
 Author: Trenser
 Date:19-May-2026
 */
+
 #pragma once
 #include <string>
 #include "Map.h"
@@ -14,6 +15,7 @@ Date:19-May-2026
 
 class Service;
 class User;
+struct SerializedServiceBooking;
 
 class ServiceBooking
 {
@@ -78,7 +80,6 @@ public:
     void setAssignedTechnicianId(const std::string& assignedTechnicianId);
     void setAssignedTechnician(User* assignedTechnician);
     void setDiscountPercentage(double discountPercentage);
-    std::string serialize() const;
-    static ServiceBooking* deserialize(const std::string&);
-    static std::string getHeaders();
+    SerializedServiceBooking serialize() const;
+    static ServiceBooking* deserialize(const SerializedServiceBooking&);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/AuthenticationManagementService.cpp

@@ -14,6 +14,28 @@ Date:19-May-2026
 #include "DataStoreLockGuard.h"
 
 User* AuthenticationManagementService::m_authenticatedUser = nullptr;
+bool AuthenticationManagementService::m_isAuthorized = false;
+EventManager AuthenticationManagementService::m_eventManager;
+HANDLE AuthenticationManagementService::m_accountDisabledEvent = NULL;
+HANDLE AuthenticationManagementService::m_notificationsAvailableEvent = NULL;
+
+
+/*
+Function: ensureAuthorization
+Description: Verifies that a user is currently authenticated before allowing
+			 access to a protected operation. Throws an exception if no
+			 authorized user session exists.
+Parameter: None
+Return type: void
+Throws: std::runtime_error - if the user is not authorized
+*/
+void AuthenticationManagementService::ensureAuthorization()
+{
+	if (!m_authenticatedUser || !m_isAuthorized)
+	{
+		throw std::runtime_error("You are not authorized to do this operation!");
+	}
+}
 
 /*
 Function: login
@@ -37,6 +59,24 @@ bool AuthenticationManagementService::login(const std::string& username, const s
 			if (password == user->getPassword())
 			{
 				m_authenticatedUser = user;
+				m_isAuthorized = true;
+				m_eventManager.initialize(
+					user->getId(),
+					[]()
+					{
+						if (m_accountDisabledEvent)
+						{
+							AuthenticationManagementService::m_isAuthorized = false;
+							SetEvent(m_accountDisabledEvent);
+						}
+					},
+					[]()
+					{
+						if (m_notificationsAvailableEvent)
+						{
+							SetEvent(m_notificationsAvailableEvent);
+						}
+					});
 				return true;
 			}
 			return false;
@@ -65,7 +105,11 @@ Return type: void
 */
 void AuthenticationManagementService::logout()
 {
+	m_eventManager.shutdown();
 	m_authenticatedUser = nullptr;
+	m_isAuthorized = false;
+	m_accountDisabledEvent = NULL;
+	m_notificationsAvailableEvent = NULL;
 }
 
 /*
@@ -77,6 +121,7 @@ Return type: void
 */
 void AuthenticationManagementService::changePassword(const std::string& newPassword)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	DataStoreLockGuard lock(m_dataStore);
 	auto& trackedUsersMap = m_dataStore.getUsers();
 	if (m_authenticatedUser == nullptr)
@@ -92,3 +137,17 @@ void AuthenticationManagementService::changePassword(const std::string& newPassw
 	trackedUsersMap.getValueAt(index).state = RecordState::MODIFIED;
 	m_dataStore.saveUsers();
 }
+
+/*
+Function: registerEvents
+Description: Registers menu event handles used to notify the active
+			 menu of account disable and notification events.
+Parameter: HANDLE accountDisabledEvent - account disabled event handle
+		   HANDLE notificationAvailableEvent - notification event handle
+Return type: void
+*/
+void AuthenticationManagementService::registerEvents(HANDLE accountDisabledEvent, HANDLE notificationAvailableEvent)
+{
+	m_accountDisabledEvent = accountDisabledEvent;
+	m_notificationsAvailableEvent = notificationAvailableEvent;
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/AuthenticationManagementService.h

@@ -9,6 +9,8 @@ Date:19-May-2026
 
 #pragma once
 #include <string>
+#include <windows.h>
+#include "EventManager.h"
 #include "DataStore.h"
 
 class User;
@@ -17,11 +19,17 @@ class AuthenticationManagementService
 {
 private:
     static User* m_authenticatedUser;
+    static bool m_isAuthorized;
+    static EventManager m_eventManager;
+    static HANDLE m_accountDisabledEvent;
+    static HANDLE m_notificationsAvailableEvent;
     DataStore& m_dataStore;
 public:
     AuthenticationManagementService() : m_dataStore(DataStore::getInstance()) {}
+    static void ensureAuthorization();
     bool login(const std::string& username, const std::string& password);
     void logout();
     void changePassword(const std::string& newPassword);
     User* getAuthenticatedUser();
+    void registerEvents(HANDLE accountDisabledEvent, HANDLE notificationAvailableEvent);
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/InventoryManagementService.cpp

@@ -14,11 +14,13 @@ Date: 22-May-2026
 #include "Factory.h"
 #include "InventoryItem.h"
 #include "InventoryManagementService.h"
+#include "AuthenticationManagementService.h"
 #include "Timestamp.h"
 #include "User.h"
 #include "Utility.h"
 #include "Vector.h"
 #include "DataStoreLockGuard.h"
+#include "EventManager.h"
 
 util::Map<std::string, User*> InventoryManagementService::m_observers{};
 
@@ -57,18 +59,19 @@ Returns:
 */
 void InventoryManagementService::sendLowStockAlerts()
 {
-	auto& inventoryItems = m_dataStore.getInventoryItems();
-	if (inventoryItems.isEmpty())
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemsMap = m_dataStore.getInventoryItems();
+	auto& trackedUserMap = m_dataStore.getUsers();
+	if (trackedInventoryItemsMap.isEmpty())
 	{
 		return;
 	}
-	int inventoryItemsSize = inventoryItems.getSize();
-	auto& usersMap = m_dataStore.getUsers();
-	int usersMapSize = usersMap.getSize();
+	int inventoryItemsSize = trackedInventoryItemsMap.getSize();
+	int usersMapSize = trackedUserMap.getSize();
 	util::Vector<User*> adminUsers;
 	for (int index = 0; index < usersMapSize; index++)
 	{
-		User* user = usersMap.getValueAt(index);
+		User* user = trackedUserMap.getValueAt(index).data;
 		if (user->getUserType() == util::UserType::ADMIN)
 		{
 			adminUsers.push_back(user);
@@ -81,7 +84,7 @@ void InventoryManagementService::sendLowStockAlerts()
 	}
 	for (int index = 0; index < inventoryItemsSize; index++)
 	{
-		InventoryItem* inventoryItem = inventoryItems.getValueAt(index);
+		InventoryItem* inventoryItem = trackedInventoryItemsMap.getValueAt(index).data;
 		if (inventoryItem && inventoryItem->getQuantity() < config::threshold::INVENTORY_LOW_STOCK_THRESHOLD)
 		{
 			sendLowStockAlertsToAdmins(*this, inventoryItem, adminUsers);
@@ -100,8 +103,12 @@ Return type: void
 */
 void InventoryManagementService::addInventoryItem(const std::string& partName, int quantity, double price)
 {
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
     InventoryItem* newItem = Factory::getObject<InventoryItem>(partName, quantity, price);
-    m_dataStore.getInventoryItems().insert(newItem->getId(), newItem);
+	trackedInventoryItemMap.insert(newItem->getId(), util::createNewRecord(newItem));
+	m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -113,16 +120,23 @@ Return type: void
 */
 void InventoryManagementService::addInventoryItemStock(const std::string& selectedItemId, int quantity)
 {
-    int index = m_dataStore.getInventoryItems().find(selectedItemId);
-    if (index != -1)
-    {
-        InventoryItem* item = m_dataStore.getInventoryItems().getValueAt(index);
-        if (item != nullptr)
-        {
-            int totalQuantity = item->getQuantity() + quantity;
-            item->setQuantity(totalQuantity);
-        }
-    }
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+	int index = trackedInventoryItemMap.find(selectedItemId);
+	if (index == -1)
+	{
+		throw std::runtime_error("Inventory update failed: Item ID '" + selectedItemId + "' not found.");
+	}
+	InventoryItem* item = trackedInventoryItemMap.getValueAt(index).data;
+	if (item == nullptr)
+	{
+		throw std::runtime_error("Inventory update failed. Item does not exist.\n");
+	}
+	int totalQuantity = item->getQuantity() + quantity;
+	item->setQuantity(totalQuantity);
+	trackedInventoryItemMap.getValueAt(index).state = RecordState::MODIFIED;
+	m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -133,7 +147,11 @@ Return type: util::Map<std::string, InventoryItem*>
 */
 util::Map<std::string, InventoryItem*> InventoryManagementService::getInventoryItems()
 {
-	return m_dataStore.getInventoryItems();
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+	auto inventoryMap = util::getObjects(trackedInventoryItemMap);
+	return inventoryMap;
 }
 
 /*
@@ -144,15 +162,22 @@ Return type: void
 */
 void InventoryManagementService::removeInventoryItem(const std::string& inventoryItemID)
 {
-    int index = m_dataStore.getInventoryItems().find(inventoryItemID);
-    if (index != -1)
-    {
-        InventoryItem* item = m_dataStore.getInventoryItems().getValueAt(index);
-        if (item != nullptr)
-        {
-            item->setState(util::State::INACTIVE);
-        }
-    }
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+	int index = trackedInventoryItemMap.find(inventoryItemID);
+	if (index == -1)
+	{
+		throw std::runtime_error("Inventory removal failed: Item ID '" + inventoryItemID + "' not found.");
+	}
+	InventoryItem* item = trackedInventoryItemMap.getValueAt(index).data;
+	if (item == nullptr)
+	{
+		throw std::runtime_error("Inventory removal failed: Item ID does not exist.");
+	}
+	item->setState(util::State::INACTIVE);
+	trackedInventoryItemMap.getValueAt(index).state = RecordState::MODIFIED;
+	m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -163,12 +188,20 @@ Return type: InventoryItem*
 */
 InventoryItem* InventoryManagementService::getInventoryItem(const std::string& inventoryItemID)
 {
-    int index = m_dataStore.getInventoryItems().find(inventoryItemID);
-    if (index != -1)
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+    int index = trackedInventoryItemMap.find(inventoryItemID);
+    if (index == -1)
     {
-        return m_dataStore.getInventoryItems().getValueAt(index);
+		return nullptr;
     }
-    return nullptr;
+	InventoryItem* inventoryItem = trackedInventoryItemMap.getValueAt(index).data;
+	if (inventoryItem == nullptr)
+	{
+		throw std::runtime_error("Item ID does not exist.");
+	}
+	return inventoryItem;
 }
 
 /*
@@ -243,6 +276,7 @@ void InventoryManagementService::sendNotification(User* user, const std::string&
 	{
 		return;
 	}
+	auto& trackedNotificationsMap = m_dataStore.getNotifications();
 	Notification* notification = Factory::getObject<Notification>(
 		user->getId(),
 		title,
@@ -252,8 +286,8 @@ void InventoryManagementService::sendNotification(User* user, const std::string&
 	{
 		throw std::runtime_error("Failed to create notification");
 	}
-	auto& trackedNotificationsMap = m_dataStore.getNotifications();
 	trackedNotificationsMap.insert(notification->getId(), util::createNewRecord(notification));
 	m_dataStore.saveNotifications();
+	EventManager::sendNotificationAvailableEvent(user->getId());
 }
 

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp

@@ -15,12 +15,15 @@ Date: 20-May-2026
 #include "Invoice.h"
 #include "JobCard.h"
 #include "PaymentManagementService.h"
+#include "AuthenticationManagementService.h"
+#include "DataStoreLockGuard.h"
 #include "Service.h"
 #include "ServiceBooking.h"
 #include "Timestamp.h"
 #include "User.h"
 #include "Utility.h"
 #include "DataStoreLockGuard.h"
+#include "EventManager.h"
 
 util::Map<std::string, User*> PaymentManagementService::m_observers{};
 
@@ -96,6 +99,7 @@ void PaymentManagementService::sendNotification(User* user, const std::string& t
 	{
 		return;
 	}
+	auto& trackedNotificationsMap = m_dataStore.getNotifications();
 	Notification* notification = Factory::getObject<Notification>(
 		user->getId(),
 		title,
@@ -105,9 +109,9 @@ void PaymentManagementService::sendNotification(User* user, const std::string& t
 	{
 		throw std::runtime_error("Failed to create notification");
 	}
-	auto& trackedNotificationsMap = m_dataStore.getNotifications();
 	trackedNotificationsMap.insert(notification->getId(), util::createNewRecord(notification));
 	m_dataStore.saveNotifications();
+	EventManager::sendNotificationAvailableEvent(user->getId());
 }
 
 /*
@@ -121,11 +125,12 @@ Returns:
 */
 void PaymentManagementService::sendPaymentReminders()
 {
-	auto& invoicesMap = m_dataStore.getInvoices();
-	int invoicesMapSize = invoicesMap.getSize();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedInvoicesMap = m_dataStore.getInvoices();
+	int invoicesMapSize = trackedInvoicesMap.getSize();
 	for (int index = 0; index < invoicesMapSize; index++)
 	{
-		const Invoice* invoice = invoicesMap.getValueAt(index);
+		const Invoice* invoice = trackedInvoicesMap.getValueAt(index).data;
 		if (invoice && invoice->getStatus() == util::PaymentStatus::PENDING)
 		{
 			util::Timestamp invoiceCreationTimestamp = invoice->getInvoiceDate();
@@ -181,6 +186,7 @@ Throws:
 */
 void PaymentManagementService::generateInvoice(ServiceBooking* booking)
 {
+	DataStoreLockGuard lock(m_dataStore);
 	if (!booking)
 	{
 		throw std::runtime_error("Invoice generation failed: booking is null.");
@@ -190,10 +196,10 @@ void PaymentManagementService::generateInvoice(ServiceBooking* booking)
 	std::string bookingID = booking->getId();
 	util::Map<std::string, Service*> servicesInTheBookedService = booking->getServices();
 	util::Map<std::string, InventoryItem*> completeInventoryItemMapOfBooking;
-	util::Map<std::string, JobCard*> currentJobCards = m_dataStore.getJobCards();
-	for (int iterator = 0; iterator < currentJobCards.getSize(); iterator++)
+	auto& currentTrackedJobCards = m_dataStore.getJobCards();
+	for (int iterator = 0; iterator < currentTrackedJobCards.getSize(); iterator++)
 	{
-		JobCard* currentJobCard = currentJobCards.getValueAt(iterator);
+		JobCard* currentJobCard = currentTrackedJobCards.getValueAt(iterator).data;
 		util::ServiceJobStatus currentJobCardStatus = currentJobCard->getStatus();
 		if (currentJobCard->getBookingId() == bookingID && currentJobCardStatus != util::ServiceJobStatus::CANCELLED && currentJobCardStatus != util::ServiceJobStatus::COMPLETED)
 		{
@@ -213,8 +219,9 @@ void PaymentManagementService::generateInvoice(ServiceBooking* booking)
 	totalServiceCost = totalLaborCost + totalPartsCost;
 	totalServiceCost -= (totalServiceCost * (discountPercentage / 100));
 	Invoice* invoice = Factory::getObject<Invoice>(bookingID, booking, util::Timestamp(), totalLaborCost, completeInventoryItemMapOfBooking, totalPartsCost, discountPercentage, totalServiceCost, util::Timestamp(), util::PaymentMode::NOTSET, util::PaymentStatus::PENDING);
-	util::Map<std::string, Invoice*>& currentInvoices = m_dataStore.getInvoices();
-	currentInvoices.insert(invoice->getId(), invoice);
+	auto& currentTrackedInvoices = m_dataStore.getInvoices();
+	currentTrackedInvoices.insert(invoice->getId(), util::createNewRecord(invoice));
+	m_dataStore.saveInvoices();
 }
 
 /*
@@ -227,11 +234,13 @@ Returns:
 */
 util::Map<std::string, Invoice*> PaymentManagementService::getInvoices(const std::string& customerID)
 {
-	util::Map<std::string, Invoice*>& currentInvoices = m_dataStore.getInvoices();
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& currentTrackedInvoices = m_dataStore.getInvoices();
 	util::Map<std::string, Invoice*> currentUserInvoices;
-	for (int iterator = 0; iterator < currentInvoices.getSize(); iterator++)
+	for (int iterator = 0; iterator < currentTrackedInvoices.getSize(); iterator++)
 	{
-		Invoice* currentInvoice = currentInvoices.getValueAt(iterator);
+		Invoice* currentInvoice = currentTrackedInvoices.getValueAt(iterator).data;
 		if (currentInvoice->getBooking()->getCustomerId() == customerID)
 		{
 			currentUserInvoices.insert(currentInvoice->getId(), currentInvoice);
@@ -254,11 +263,14 @@ Throws:
 */
 void PaymentManagementService::completePayment(const std::string& invoiceID, util::PaymentMode paymentMode)
 {
-	auto& currentInvoices = m_dataStore.getInvoices();
-	int invoiceIndex = currentInvoices.find(invoiceID);
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& currentTrackedInvoices = m_dataStore.getInvoices();
+	int invoiceIndex = currentTrackedInvoices.find(invoiceID);
 	if (invoiceIndex != -1)
 	{
-		Invoice* invoice = currentInvoices.getValueAt(invoiceIndex);
+		auto& trackedInvoice = currentTrackedInvoices.getValueAt(invoiceIndex);
+		Invoice* invoice = trackedInvoice.data;
 		if (invoice && invoice->getStatus() != util::PaymentStatus::PAID)
 		{
 			User* currentUser = invoice->getBooking()->getCustomer();
@@ -269,25 +281,31 @@ void PaymentManagementService::completePayment(const std::string& invoiceID, uti
 			title = "Payment successful";
 			message = "Payment successful for Invoice ID " + invoiceID;
 			sendNotification(currentUser, title, message);
+			trackedInvoice.state = RecordState::MODIFIED;
 		}
 	}
 	else
 	{
 		throw std::runtime_error("Payment failed: invalid invoice ID.");
 	}
+	m_dataStore.saveInvoices();
 }
 
 /*
-Function: getAllInvoice
+Function: getAllInvoices
 Description: Provides access to all invoices stored in the data store.
 Parameters:
 	- none
 Returns:
-	- util::Map<std::string, Invoice*>&: Map of invoice IDs to invoice objects
+	- util::Map<std::string, Invoice*>: Map of invoice IDs to invoice objects
 */
-util::Map<std::string, Invoice*>& PaymentManagementService::getAllInvoices()
+util::Map<std::string, Invoice*> PaymentManagementService::getAllInvoices()
 {
-	return m_dataStore.getInvoices();
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	util::Map<std::string, Invoice*> invoices;
+	invoices = util::getObjects(m_dataStore.getInvoices());
+	return invoices;
 }
 
 /*
@@ -303,20 +321,25 @@ Throws:
 */
 void PaymentManagementService::confirmPayment(const std::string& invoiceID)
 {
-	auto& currentInvoices = m_dataStore.getInvoices();
-	int invoiceIndex = currentInvoices.find(invoiceID);
+    AuthenticationManagementService::ensureAuthorization();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& currentTrackedInvoices = m_dataStore.getInvoices();
+	int invoiceIndex = currentTrackedInvoices.find(invoiceID);
 	if (invoiceIndex == -1)
 	{
 		throw std::runtime_error("Payment confirmation failed: invalid invoice ID.");
 	}
-	Invoice* invoice = currentInvoices.getValueAt(invoiceIndex);
+	auto& trackedInvoice = currentTrackedInvoices.getValueAt(invoiceIndex);
+	Invoice* invoice = trackedInvoice.data;
 	if (!invoice || invoice->getStatus() != util::PaymentStatus::PAID)
 	{
 		throw std::runtime_error("Payment confirmation failed: invoice is not awaiting confirmation.");
 	}
 	User* currentUser = invoice->getBooking()->getCustomer();
 	invoice->setStatus(util::PaymentStatus::COMPLETED);
+	trackedInvoice.state = RecordState::MODIFIED;
 	std::string title = "Payment Confirmed";
 	std::string message = "Payment Confirmed for Invoice ID " + invoiceID;
 	sendNotification(currentUser, title, message);
+	m_dataStore.saveInvoices();
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.h

@@ -27,7 +27,7 @@ public:
     void generateInvoice(ServiceBooking* booking);
     util::Map<std::string, Invoice*> getInvoices(const std::string& customerID);
     void completePayment(const std::string& invoiceID, util::PaymentMode paymentMode);
-    util::Map<std::string, Invoice*>& getAllInvoices();
+    util::Map<std::string, Invoice*> getAllInvoices();
     void confirmPayment(const std::string& invoiceID);
     void sendPaymentReminders();
     void sendNotification(User* user, const std::string& title, const std::string& message) override;

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/ServiceManagementService.cpp

@@ -24,8 +24,34 @@ Date:19-May-2026
 #include "Timestamp.h"
 #include "User.h"
 #include "UserManagementService.h"
-#include "Utility.h"
 #include "DataStoreLockGuard.h"
+#include "Utility.h"
+#include "EventManager.h"
+
+/*
+Function: notifyAllAdmins
+Description: Sends a notification to all users with the ADMIN role.
+             Iterates through the provided user collection and delivers
+             the specified notification to each administrator using the
+             ServiceManagementService notification mechanism.
+Parameter: const std::string& title - notification title
+Parameter: const std::string& message - notification message
+Parameter: const util::Map<std::string, TrackedRecord<User>>& users - collection of tracked users
+Parameter: ServiceManagementService* serviceManagementService - service used to dispatch notifications
+Return type: void
+*/
+static void notifyAllAdmins(const std::string& title, const std::string& message, const util::Map<std::string, TrackedRecord<User>>& users, ServiceManagementService* serviceManagementService)
+{
+    int numberOfUsers = users.getSize();
+    for (int index = 0; index < numberOfUsers; index++)
+    {
+        User* user = users.getValueAt(index).data;
+        if (user->getUserType() == util::UserType::ADMIN)
+        {
+            serviceManagementService->sendNotification(user, title, message);
+        }
+    }
+}
 
 /*
 Function: purchaseService
@@ -40,24 +66,26 @@ Return type: void
 */
 void ServiceManagementService::purchaseService(const util::Vector<std::string>& serviceIDs, const std::string& vehicleNumber, const std::string& vehicleBrand, const std::string& vehicleModel)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	AuthenticationManagementService m_authenticationManagementService;
 	auto authenticatedUser = m_authenticationManagementService.getAuthenticatedUser();
 	if (authenticatedUser == nullptr)
 	{
 		throw std::runtime_error("No user is currently logged in!");
 	}
-	auto& servicesMap = m_dataStore.getServices();
-	auto& serviceBookingMap = m_dataStore.getServiceBookings();
+    DataStoreLockGuard lock(m_dataStore);
+	auto& trackedServicesMap = m_dataStore.getServices();
+	auto& trackedServiceBookingMap = m_dataStore.getServiceBookings();
 	util::Map<std::string, Service*> selectedServices;
 	int selectedServicesCount = serviceIDs.getSize();
 	for (int index = 0; index < selectedServicesCount; index++)
 	{
-		int serviceIndex = servicesMap.find(serviceIDs[index]);
+		int serviceIndex = trackedServicesMap.find(serviceIDs[index]);
 		if (serviceIndex == -1)
 		{
 			throw std::runtime_error("Service not found!");
 		}
-		Service* service = servicesMap.getValueAt(serviceIndex);
+		Service* service = trackedServicesMap.getValueAt(serviceIndex).data;
 		selectedServices[service->getId()] = service;
 	}
 	ServiceBooking* serviceBooking = Factory::getObject<ServiceBooking>(util::ServiceJobStatus::PENDING, selectedServices, authenticatedUser->getId(), authenticatedUser, vehicleNumber, vehicleBrand, vehicleModel, 0);
@@ -65,10 +93,12 @@ void ServiceManagementService::purchaseService(const util::Vector<std::string>&
 	{
 		throw std::runtime_error("Failed to create service booking");
 	}
-	serviceBookingMap[serviceBooking->getId()] = serviceBooking;
+	trackedServiceBookingMap[serviceBooking->getId()] =  util::createNewRecord(serviceBooking);
     std::string title = "Service Booking succeeded";
     std::string message = "Your service booking has been successfully placed with ID " + serviceBooking->getId();
     sendNotification(authenticatedUser, title, message);
+    m_dataStore.saveServiceBookings();
+    notifyAllAdmins("New Service Order Available", "A new service order has been placed with Service Booking ID " + serviceBooking->getId(), m_dataStore.getUsers(), this);
 }
 
 /*
@@ -84,30 +114,34 @@ Return type: void
 */
 void ServiceManagementService::purchaseComboPackage(const std::string& comboPackageID, const std::string& vehicleNumber, const std::string& vehicleBrand, const std::string& vehicleModel)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	AuthenticationManagementService m_authenticationManagementService;
 	auto authenticatedUser = m_authenticationManagementService.getAuthenticatedUser();
 	if (authenticatedUser == nullptr)
 	{
 		throw std::runtime_error("No user is currently logged in!");
 	}
-	auto& comboPackagesMap = m_dataStore.getComboPackages();
-	auto& serviceBookingMap = m_dataStore.getServiceBookings();
-	int comboPackageIndex = comboPackagesMap.find(comboPackageID);
+    DataStoreLockGuard lock(m_dataStore);
+	auto& trackedComboPackagesMap = m_dataStore.getComboPackages();
+	auto& trackedServiceBookingMap = m_dataStore.getServiceBookings();
+	int comboPackageIndex = trackedComboPackagesMap.find(comboPackageID);
 	if (comboPackageIndex == -1)
 	{
 		throw std::runtime_error("Combo Package not found!");
 	}
-	const ComboPackage* comboPackage = comboPackagesMap[comboPackageID];
+	const ComboPackage* comboPackage = trackedComboPackagesMap[comboPackageID].data;
 	util::Map<std::string, Service*> selectedServices = comboPackage->getServices();
 	ServiceBooking* serviceBooking = Factory::getObject<ServiceBooking>(util::ServiceJobStatus::PENDING, selectedServices, authenticatedUser->getId(), authenticatedUser, vehicleNumber, vehicleBrand, vehicleModel, comboPackage->getDiscountPercentage());
 	if (serviceBooking == nullptr)
 	{
 		throw std::runtime_error("Failed to create combo package service booking");
 	}
-	serviceBookingMap[serviceBooking->getId()] = serviceBooking;
+	trackedServiceBookingMap[serviceBooking->getId()] = util::createNewRecord(serviceBooking);
     std::string title = "Combo Package Service Booking succeeded";
     std::string message = "Your service booking for the combo package has been successfully placed with ID " + serviceBooking->getId();
     sendNotification(authenticatedUser, title, message);
+    m_dataStore.saveServiceBookings();
+    notifyAllAdmins("New Combo Package Order Available", "A new combo package order has been placed with Service Booking ID " + serviceBooking->getId(), m_dataStore.getUsers(), this);
 }
 
 util::Map<std::string, User*> ServiceManagementService::m_observers{};
@@ -184,6 +218,7 @@ void ServiceManagementService::sendNotification(User* user, const std::string& t
     {
         return;
     }
+    auto& trackedNotificationsMap = m_dataStore.getNotifications();
     Notification* notification = Factory::getObject<Notification>(
         user->getId(),
         title,
@@ -193,9 +228,9 @@ void ServiceManagementService::sendNotification(User* user, const std::string& t
     {
         throw std::runtime_error("Failed to create notification");
     }
-    auto& trackedNotificationsMap = m_dataStore.getNotifications();
     trackedNotificationsMap.insert(notification->getId(), util::createNewRecord(notification));
     m_dataStore.saveNotifications();
+    EventManager::sendNotificationAvailableEvent(user->getId());
 }
 
 /*
@@ -205,7 +240,7 @@ Description: Restores inventory quantities for all required items in the service
 Parameter: ServiceBooking* booking - Pointer to the booking whose inventory items need to be restored
 Return type: void
 */
-static void restoreInventory(ServiceBooking* booking)
+static void restoreInventory(ServiceBooking* booking, util::Map<std::string, TrackedRecord<InventoryItem>>& trackedInventoryItems)
 {
     const int INCREMENT_VALUE = 1;
     if (!booking) 
@@ -224,9 +259,17 @@ static void restoreInventory(ServiceBooking* booking)
         for (int InventoryIterator = 0; InventoryIterator < items.getSize(); ++InventoryIterator)
         {
             InventoryItem* item = items.getValueAt(InventoryIterator);
+            const std::string& currentItemId = item->getId();
+            int itemIndex = trackedInventoryItems.find(currentItemId);
+            if (itemIndex == -1)
+            {
+                continue;
+            }
+            auto& currentTrackedInventoryItem = trackedInventoryItems.getValueAt(itemIndex);
             if (item)
             {
                 item->setQuantity(item->getQuantity() + INCREMENT_VALUE);
+                currentTrackedInventoryItem.state = RecordState::MODIFIED;
             }
         }
     }
@@ -244,23 +287,28 @@ Parameters:
     util::UserType userType - Type of user initiating cancellation (CUSTOMER or TECHNICIAN)
 Return type: void
 */
-static void processBookingCancellation(ServiceBooking* booking,
-    util::Map<std::string, JobCard*>& jobs,
+static void processBookingCancellation(TrackedRecord<ServiceBooking>& trackedBooking,
+    util::Map<std::string, TrackedRecord<JobCard>>& jobs,
     ServiceManagementService& currentService,
-    util::UserType userType)
+    util::UserType userType,
+    util::Map<std::string, TrackedRecord<InventoryItem>>& trackedInventoryItems)
 {
+    ServiceBooking* booking = trackedBooking.data;
     if (!booking)
     {
         return;
     }
+    const std::string& bookingId = booking->getId();
     for (int jobIterator = 0; jobIterator < jobs.getSize(); ++jobIterator)
     {
-        JobCard* jobCard = jobs.getValueAt(jobIterator);
+        auto& trackedJobCard = jobs.getValueAt(jobIterator);
+        JobCard* jobCard = trackedJobCard.data;
         if (!jobCard || jobCard->getBookingId() != booking->getId() || jobCard->getStatus() == util::ServiceJobStatus::CANCELLED)
         {
             continue;
         }
         jobCard->setStatus(util::ServiceJobStatus::CANCELLED);
+        trackedJobCard.state = RecordState::MODIFIED;
         if (userType == util::UserType::CUSTOMER)
         {
             if (User* technician = booking->getAssignedTechnician())
@@ -293,7 +341,8 @@ static void processBookingCancellation(ServiceBooking* booking,
     }
     booking->setAssignedTechnician(nullptr);
     booking->setAssignedTechnicianId("");
-    restoreInventory(booking);
+    trackedBooking.state = RecordState::MODIFIED;
+    restoreInventory(booking, trackedInventoryItems);
 }
 
 /*
@@ -306,22 +355,25 @@ Return type: void
 */
 void ServiceManagementService::cancelCustomerServiceBookings(const std::string& customerID)
 {
-    auto& users = m_dataStore.getUsers();
-    int userIndex = users.find(customerID);
+    DataStoreLockGuard lock(m_dataStore);
+    auto& trackedUsers = m_dataStore.getUsers();
+    int userIndex = trackedUsers.find(customerID);
     if (userIndex == -1)
     {
         throw std::runtime_error("User not found: " + customerID);
     }
-    User* customer = users.getValueAt(userIndex);
+    User* customer = trackedUsers.getValueAt(userIndex).data;
     if (!customer)
     {
         throw std::runtime_error("User not found: " + customerID);
     }
-    auto& bookings = m_dataStore.getServiceBookings();
-    auto& jobs = m_dataStore.getJobCards();
-    for (int iteratorOne = 0; iteratorOne < bookings.getSize(); iteratorOne++)
+    auto& trackedBookings = m_dataStore.getServiceBookings();
+    auto& trackedJobs = m_dataStore.getJobCards();
+    auto& trackedInventoryItems = m_dataStore.getInventoryItems();
+    for (int iteratorOne = 0; iteratorOne < trackedBookings.getSize(); iteratorOne++)
     {
-        ServiceBooking* booking = bookings.getValueAt(iteratorOne);
+        auto& trackedBooking = trackedBookings.getValueAt(iteratorOne);
+        ServiceBooking* booking = trackedBooking.data;
         if (!booking)
         {
             continue;
@@ -336,8 +388,12 @@ void ServiceManagementService::cancelCustomerServiceBookings(const std::string&
         {
             continue;
         }
-        processBookingCancellation(booking, jobs, *this, util::UserType::CUSTOMER);
+        processBookingCancellation(trackedBooking, trackedJobs, *this, util::UserType::CUSTOMER, trackedInventoryItems);
     }
+    m_dataStore.saveUsers();
+    m_dataStore.saveServiceBookings();
+    m_dataStore.saveJobCards();
+    m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -349,22 +405,25 @@ Return type: void
 */
 void ServiceManagementService::cancelTechnicianJobs(const std::string& technicianID)
 {
-    auto& users = m_dataStore.getUsers();
-    int userIndex = users.find(technicianID);
+    DataStoreLockGuard lock(m_dataStore);
+    auto& trackedUsers = m_dataStore.getUsers();
+    int userIndex = trackedUsers.find(technicianID);
     if (userIndex == -1)
     {
         throw std::runtime_error("User not found: " + technicianID);
     }
-    User* technician = users.getValueAt(userIndex);
+    User* technician = trackedUsers.getValueAt(userIndex).data;
     if (!technician)
     {
         throw std::runtime_error("User not found: " + technicianID);
     }
-    auto& bookings = m_dataStore.getServiceBookings();
-    auto& jobs = m_dataStore.getJobCards();
-    for (int iteratorOne = 0; iteratorOne < bookings.getSize(); iteratorOne++)
+    auto& trackedBookings = m_dataStore.getServiceBookings();
+    auto& trackedJobs = m_dataStore.getJobCards();
+    auto& trackedInventoryItems = m_dataStore.getInventoryItems();
+    for (int iteratorOne = 0; iteratorOne < trackedBookings.getSize(); iteratorOne++)
     {
-        ServiceBooking* booking = bookings.getValueAt(iteratorOne);
+        auto& trackedBooking = trackedBookings.getValueAt(iteratorOne);
+        ServiceBooking* booking = trackedBooking.data;
         if (!booking)
         {
             continue;
@@ -385,8 +444,12 @@ void ServiceManagementService::cancelTechnicianJobs(const std::string& technicia
         {
             continue;
         }
-        processBookingCancellation(booking, jobs, *this, util::UserType::TECHNICIAN);
+        processBookingCancellation(trackedBooking, trackedJobs, *this, util::UserType::TECHNICIAN, trackedInventoryItems);
     }
+    m_dataStore.saveUsers();
+    m_dataStore.saveInventoryItems();
+    m_dataStore.saveServiceBookings();
+    m_dataStore.saveJobCards();
 }
 
 /*
@@ -400,6 +463,8 @@ Return type: void
 */
 void ServiceManagementService::createComboPackage(const std::string& packageName, const util::Vector<std::string>& serviceIDsInNewCombo, double discountPercentage)
 {
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
     if (packageName.empty())
     {
         throw std::invalid_argument("The Combo Package Name cannot be empty.\n");
@@ -412,19 +477,19 @@ void ServiceManagementService::createComboPackage(const std::string& packageName
     {
         throw std::invalid_argument("Discount percentage must be between 0 and 100.");
     }
-    auto& servicesMap = m_dataStore.getServices();
+    auto& trackedServicesMap = m_dataStore.getServices();
     for (int index = 0; index < serviceIDsInNewCombo.getSize(); index++)
     {
-        const std::string serviceid = serviceIDsInNewCombo[index];
-        if (servicesMap.find(serviceid) == -1)
+        const std::string& serviceid = serviceIDsInNewCombo[index];
+        if (trackedServicesMap.find(serviceid) == -1)
         {
             throw std::runtime_error("Service ID not found: " + serviceid);
         }
     }
-    auto& comboPackageMap = m_dataStore.getComboPackages();
-    for (int iterator = 0; iterator < comboPackageMap.getSize(); iterator++)
+    auto& trackedComboPackageMap = m_dataStore.getComboPackages();
+    for (int iterator = 0; iterator < trackedComboPackageMap.getSize(); iterator++)
     {
-        ComboPackage* existingCombos = comboPackageMap.getValueAt(iterator);
+        ComboPackage* existingCombos = trackedComboPackageMap.getValueAt(iterator).data;
         const util::Map<std::string, Service*>& servicesInsideExistingCombos = existingCombos->getServices();
         if (servicesInsideExistingCombos.getSize() == serviceIDsInNewCombo.getSize())
         {
@@ -448,15 +513,16 @@ void ServiceManagementService::createComboPackage(const std::string& packageName
     for (int iteratorOne = 0; iteratorOne < serviceIDsInNewCombo.getSize(); iteratorOne++)
     {
         const std::string& serviceId = serviceIDsInNewCombo[iteratorOne];
-        int serviceIndex = servicesMap.find(serviceId);
+        int serviceIndex = trackedServicesMap.find(serviceId);
         if (serviceIndex == -1)
         {
             throw std::runtime_error("Service ID not found: " + serviceId);
         }
-        selectedServices.insert(serviceId, servicesMap.getValueAt(serviceIndex));
+        selectedServices.insert(serviceId, trackedServicesMap.getValueAt(serviceIndex).data);
     }
     ComboPackage* newComboPackage = Factory::getObject<ComboPackage>(packageName, discountPercentage, selectedServices);
-    comboPackageMap.insert(newComboPackage->getId(), newComboPackage);
+    trackedComboPackageMap.insert(newComboPackage->getId(), util::createNewRecord(newComboPackage));
+    m_dataStore.saveComboPackages();
 }
 
 /*
@@ -467,7 +533,11 @@ Return type: util::Map<std::string, ComboPackage*>
 */
 util::Map<std::string, ComboPackage*> ServiceManagementService::getComboPackages()
 {
-    return m_dataStore.getComboPackages();
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+    util::Map<std::string, ComboPackage*> comboPackages;
+    comboPackages = util::getObjects(m_dataStore.getComboPackages());
+    return comboPackages;
 }
 
 /*
@@ -478,14 +548,18 @@ Return type: void
 */
 void ServiceManagementService::removeComboPackage(const std::string& comboPackageID)
 {
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
     bool removed = false;
-    util::Map<std::string, ComboPackage*>& currentComboPackages = m_dataStore.getComboPackages();
-    for (int iterator = 0; iterator < currentComboPackages.getSize(); iterator++)
+    auto& trackedComboPackages = m_dataStore.getComboPackages();
+    for (int iterator = 0; iterator < trackedComboPackages.getSize(); iterator++)
     {
-        ComboPackage* currentComboPackage = currentComboPackages.getValueAt(iterator);
+        auto& comboPackage = trackedComboPackages.getValueAt(iterator);
+        ComboPackage* currentComboPackage = comboPackage.data;
         if (currentComboPackage && currentComboPackage->getId() == comboPackageID)
         {
             currentComboPackage->setState(util::State::INACTIVE);
+            comboPackage.state = RecordState::MODIFIED;
             removed = true;
             break;
         }
@@ -494,6 +568,7 @@ void ServiceManagementService::removeComboPackage(const std::string& comboPackag
     {
         throw std::runtime_error("Combo package with ID '" + comboPackageID + "' not found.");
     }
+    m_dataStore.saveComboPackages();
 }
 
 /*
@@ -506,7 +581,11 @@ Returns:
 */
 util::Map<std::string, ServiceBooking*> ServiceManagementService::getServiceBookings()
 {
-	return m_dataStore.getServiceBookings();
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+    util::Map<std::string, ServiceBooking*> serviceBookings;
+    serviceBookings = util::getObjects(m_dataStore.getServiceBookings());
+    return serviceBookings;
 }
 
 /*
@@ -519,6 +598,7 @@ Returns:
 */
 ServiceBooking* ServiceManagementService::getServiceBooking(const std::string& serviceID)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	auto currentServiceBookings = getServiceBookings();
 	for (int iterator = 0; iterator < currentServiceBookings.getSize(); iterator++)
 	{
@@ -545,13 +625,28 @@ Throws:
 */
 void ServiceManagementService::createJobCard(const std::string& bookingID, const std::string& technicianID, const std::string& serviceID)
 {
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
 	UserManagementService m_userManagementService;
 	ServiceBooking* currentBooking = getServiceBooking(bookingID);
-	auto& currentJobCards = m_dataStore.getJobCards();
-	if (currentBooking == nullptr)
-	{
-		throw std::runtime_error("Service Booking not available");
-	}
+    std::string title, message;
+    if (currentBooking == nullptr)
+    {
+        throw std::runtime_error("Service Booking not available");
+    }
+    if (currentBooking->getStatus() == util::ServiceJobStatus::CANCELLED)
+    {
+        throw std::runtime_error("Cannot create job card. Service Booking was cancelled!");
+    }
+	auto& currentTrackedJobCards = m_dataStore.getJobCards();
+    auto& currentTrackedInventoryItems = m_dataStore.getInventoryItems();
+    auto& currentTrackedServiceBookings = m_dataStore.getServiceBookings();
+    int currentTrackedServiceBookingIndex = currentTrackedServiceBookings.find(bookingID);
+    if (currentTrackedServiceBookingIndex == -1)
+    {
+        throw std::runtime_error("Invalid service booking id.");
+    }
+    auto& currentTrackedServiceBooking = currentTrackedServiceBookings.getValueAt(currentTrackedServiceBookingIndex);
 	auto& currentServices = currentBooking->getServices();
 	if (currentServices.find(serviceID) == -1)
 	{
@@ -576,33 +671,54 @@ void ServiceManagementService::createJobCard(const std::string& bookingID, const
 	for (int iterator = 0; iterator < inventoryItems.getSize(); iterator++)
 	{
 		InventoryItem* currentInventoryItem = inventoryItems.getValueAt(iterator);
+        const std::string& currentInventoryItemId = inventoryItems.getKeyAt(iterator);
 		if (currentInventoryItem)
 		{
+            int trackedCurrentInventoryItemIndex = currentTrackedInventoryItems.find(currentInventoryItemId);
+            if (trackedCurrentInventoryItemIndex == -1)
+            {
+                throw std::runtime_error("Invalid inventory item index.");
+            }
+            auto& trackedCurrentInventoryItem = currentTrackedInventoryItems.getValueAt(trackedCurrentInventoryItemIndex);
 			int currentStockQuantity = currentInventoryItem->getQuantity();
 			currentInventoryItem->setQuantity(currentStockQuantity - 1);
+            trackedCurrentInventoryItem.state = RecordState::MODIFIED;
 		}
 	}
-	currentBooking->setAssignedTechnician(selectedTechnician);
-	currentBooking->setAssignedTechnicianId(selectedTechnician->getId());
+    const User* currentAssignedTechnician = currentBooking->getAssignedTechnician();
+    const std::string& currentAssignedTechnicianId = currentBooking->getAssignedTechnicianId();
+    if (!currentAssignedTechnician && currentAssignedTechnicianId.empty())
+    {
+        currentBooking->setAssignedTechnician(selectedTechnician);
+        currentBooking->setAssignedTechnicianId(selectedTechnician->getId());
+        title = "Technician assigned";
+        message = "A technician has been assigned to your Service Booking with ID " + bookingID;
+        sendNotification(currentBooking->getCustomer(), title, message);
+    }
+
     if (currentBooking->getStatus() == util::ServiceJobStatus::PENDING)
     {
         currentBooking->setStatus(util::ServiceJobStatus::STARTED);
     }
-	std::string title = "Job card created";
-	std::string message = "Job card created for the service and you are assigned for that.";
+    currentTrackedServiceBooking.state = RecordState::MODIFIED;
 	JobCard* jobCard = Factory::getObject<JobCard>(bookingID, currentBooking, currentService, serviceID, technicianID, selectedTechnician, util::Timestamp(), util::ServiceJobStatus::STARTED, util::Timestamp());
 	if (jobCard)
 	{
-		currentJobCards.insert(jobCard->getId(), jobCard);
+        title = "Job Card Assigned";
+        message = "A new Job Card (ID: " + jobCard->getId() +
+            ") has been created for Service " + serviceID +
+            " in Booking " + bookingID +
+            ". You have been assigned to this job.";
+		currentTrackedJobCards.insert(jobCard->getId(), util::createNewRecord(jobCard));
 		sendNotification(selectedTechnician, title, message);
 	}
 	else
 	{
 		throw std::runtime_error("Failed to create job card.");
 	}
-    title = "Technician assigned";
-    message = "A technician has been assigned to your Service Booking with ID " + bookingID;
-    sendNotification(currentBooking->getCustomer(), title, message);
+    m_dataStore.saveJobCards();
+    m_dataStore.saveServiceBookings();
+    m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -620,15 +736,18 @@ Throws:
 */
 void ServiceManagementService::createService(const std::string& name, const util::Vector<std::string>& inventoryItemIDs, double laborCost)
 {
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
 	util::Map<std::string, InventoryItem*> currentServiceInventoryItems;
-	auto inventoryItems = m_dataStore.getInventoryItems();
+	auto& trackedInventoryItems = m_dataStore.getInventoryItems();
+    auto& currentServices = m_dataStore.getServices();
 	for (int iteratorOne =0; iteratorOne < inventoryItemIDs.getSize(); iteratorOne++)
 	{
 		std::string currentItemID = inventoryItemIDs[iteratorOne];
 		bool itemFound = false;
-		for (int iteratorTwo = 0; iteratorTwo < inventoryItems.getSize(); iteratorTwo++)
+		for (int iteratorTwo = 0; iteratorTwo < trackedInventoryItems.getSize(); iteratorTwo++)
 		{
-			InventoryItem* currentInventoryItem = inventoryItems.getValueAt(iteratorTwo);
+			InventoryItem* currentInventoryItem = trackedInventoryItems.getValueAt(iteratorTwo).data;
 			if (currentInventoryItem && currentInventoryItem->getId() == currentItemID)
 			{
 				itemFound = true;
@@ -646,12 +765,12 @@ void ServiceManagementService::createService(const std::string& name, const util
 	{
 		throw std::runtime_error("Unable to create new service.");
 	}
-	util::Map<std::string, Service*>& currentServices = m_dataStore.getServices();
 	if (currentServices.find(newService->getId()) != -1)
 	{
 		throw std::runtime_error("Service with this ID Already exists.");
 	}
-	currentServices.insert(newService->getId(), newService);
+	currentServices.insert(newService->getId(), util::createNewRecord(newService));
+    m_dataStore.saveServices();
 }
 
 /*
@@ -664,7 +783,11 @@ Returns:
 */
 util::Map<std::string, Service*> ServiceManagementService::getServices()
 {
-	return m_dataStore.getServices();
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+    util::Map<std::string, Service*> services;
+    services = util::getObjects(m_dataStore.getServices());
+    return services;
 }
 
 /*
@@ -679,14 +802,20 @@ Throws:
 */
 void ServiceManagementService::removeService(const std::string& serviceID)
 {
-	util::Map<std::string, Service*>& currentServices = m_dataStore.getServices();
-    util::Map<std::string, ComboPackage*>& currentComboPackages =  m_dataStore.getComboPackages();
-	if (currentServices.find(serviceID) != -1)
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+	auto& currentTrackedServices = m_dataStore.getServices();
+    auto& currentTrackedComboPackages =  m_dataStore.getComboPackages();
+	if (currentTrackedServices.find(serviceID) != -1)
 	{
-		currentServices.getValueAt(currentServices.find(serviceID))->setState(util::State::INACTIVE);
-        for (int iterator = 0; iterator < currentComboPackages.getSize(); iterator++)
+        int serviceIndex, comboPackageIndex;
+        serviceIndex = currentTrackedServices.find(serviceID);
+		currentTrackedServices.getValueAt(serviceIndex).data->setState(util::State::INACTIVE);
+        currentTrackedServices.getValueAt(serviceIndex).state = RecordState::MODIFIED;
+        for (int iterator = 0; iterator < currentTrackedComboPackages.getSize(); iterator++)
         {
-            ComboPackage* currentComboPackage = currentComboPackages.getValueAt(iterator);
+            comboPackageIndex = iterator;
+            ComboPackage* currentComboPackage = currentTrackedComboPackages.getValueAt(iterator).data;
             if (currentComboPackage && currentComboPackage->getState() == util::State::ACTIVE)
             {
                 util::Map<std::string, Service*> currentServices = currentComboPackage->getServices();
@@ -696,6 +825,7 @@ void ServiceManagementService::removeService(const std::string& serviceID)
                     if (currentService->getId() == serviceID)
                     {
                         currentComboPackage->setState(util::State::INACTIVE);
+                        currentTrackedComboPackages.getValueAt(comboPackageIndex).state = RecordState::MODIFIED;
                         break;
                     }
                 }
@@ -706,6 +836,63 @@ void ServiceManagementService::removeService(const std::string& serviceID)
 	{
 		throw std::runtime_error("Service not found.");
 	}
+    m_dataStore.saveServices();
+    m_dataStore.saveComboPackages();
+}
+
+/*
+Function: removeServiceBooking
+Description: Removes a pending service booking by its ID.
+             Cancels only if status is PENDING, otherwise throws exceptions
+             for invalid states. Sends notification to the customer and
+             persists changes.
+Parameter: const std::string& bookingID - ID of the service booking
+Return type: void
+*/
+void ServiceManagementService::removeServiceBooking(const std::string& bookingID)
+{
+    DataStoreLockGuard lock(m_dataStore);
+    auto& trackedServiceBookings = m_dataStore.getServiceBookings();
+    bool serviceBookingRemoved = false;
+    for (int iterator = 0; iterator < trackedServiceBookings.getSize(); iterator++)
+    {
+        auto& currentTrackedServiceBooking = trackedServiceBookings.getValueAt(iterator);
+        ServiceBooking* currentServiceBooking = currentTrackedServiceBooking.data;
+        if (currentServiceBooking && currentServiceBooking->getId() == bookingID)
+        {
+            if (currentServiceBooking->getStatus() == util::ServiceJobStatus::PENDING)
+            {
+                const std::string title = "Service Booking Cancelled";
+                const std::string message = "Service Booking (ID: " + bookingID + ") has been successfully cancelled";
+                currentServiceBooking->setStatus(util::ServiceJobStatus::CANCELLED);
+                currentTrackedServiceBooking.state = RecordState::MODIFIED;
+                serviceBookingRemoved = true;
+                sendNotification(currentServiceBooking->getCustomer(), title, message);
+                break;
+            }
+            else if(currentServiceBooking->getStatus() == util::ServiceJobStatus::COMPLETED)
+            {
+                throw std::runtime_error("Unable to cancel completed service booking.");
+            }
+            else if (currentServiceBooking->getStatus() == util::ServiceJobStatus::STARTED)
+            {
+                throw std::runtime_error("Unable to cancel started service booking.");
+            }
+            else if (currentServiceBooking->getStatus() == util::ServiceJobStatus::IN_PROGRESS)
+            {
+                throw std::runtime_error("Unable to cancel currently Inprogress service booking.");
+            }
+            else
+            {
+                throw std::runtime_error("Service Booking already cancelled.");
+            }
+        }
+    }
+    if (!serviceBookingRemoved)
+    {
+        throw std::runtime_error("Unable to cancel service booking.");
+    }
+    m_dataStore.saveServiceBookings();
 }
 
 /*
@@ -718,6 +905,7 @@ Returns:
 */
 util::Map<std::string, ServiceBooking*> ServiceManagementService::getServiceBookings(const std::string& customerID)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	util::Map<std::string, ServiceBooking*> currentServiceBookings = getServiceBookings();
 	util::Map<std::string, ServiceBooking*> currentUserServiceBookings;
 	if (currentServiceBookings.getSize() != 0)
@@ -744,11 +932,13 @@ Returns:
 */
 util::Map<std::string, JobCard*> ServiceManagementService::getJobCards(const std::string& technicianID)
 {
-	util::Map<std::string, JobCard*> jobCards = m_dataStore.getJobCards();
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+	auto& trackedJobCards = m_dataStore.getJobCards();
 	util::Map<std::string, JobCard*> technicianJobCards;
-	for (int iterator = 0; iterator < jobCards.getSize(); iterator++)
+	for (int iterator = 0; iterator < trackedJobCards.getSize(); iterator++)
 	{
-		JobCard* currentJobCard = jobCards.getValueAt(iterator);
+		JobCard* currentJobCard = trackedJobCards.getValueAt(iterator).data;
 		if (currentJobCard->getTechnicianId() == technicianID)
 		{
 			technicianJobCards.insert(currentJobCard->getId(), currentJobCard);
@@ -797,53 +987,68 @@ Returns:
 */
 void ServiceManagementService::updateJobStatus(const std::string& jobID)
 {
-	AuthenticationManagementService authenticationManagementService;
-	PaymentManagementService paymentManagementService;
-	bool jobStatusUpdated = false, serviceBookingCompleted;
-	JobCard* currentJob;
-	User* currentTechnician = authenticationManagementService.getAuthenticatedUser();
-	if (currentTechnician == nullptr)
-	{
-		throw std::runtime_error("Unable to fetch current technician.");
-	}
-	util::Map<std::string, JobCard*> currentAssignedJobs = getJobCards(currentTechnician->getId());
-	if (currentAssignedJobs.getSize() == 0)
-	{
-		throw std::runtime_error("No job cards assigned to the technician.");
-	}
-	if (currentAssignedJobs.find(jobID) != -1)
-	{
-		currentJob = currentAssignedJobs.getValueAt(currentAssignedJobs.find(jobID));
-		if (currentJob == nullptr)
-		{
-			throw std::runtime_error("Unable to fetch current job.");
-		}
-		if (currentJob->getStatus() == util::ServiceJobStatus::STARTED)
-		{
-			currentJob->setStatus(util::ServiceJobStatus::IN_PROGRESS);
-			jobStatusUpdated = true;
-		}
+    AuthenticationManagementService::ensureAuthorization();
+    DataStoreLockGuard lock(m_dataStore);
+    AuthenticationManagementService authenticationManagementService;
+    PaymentManagementService paymentManagementService;
+    bool jobStatusUpdated = false, serviceBookingCompleted;
+    User* currentTechnician = authenticationManagementService.getAuthenticatedUser();
+    if (currentTechnician == nullptr)
+    {
+        throw std::runtime_error("Unable to fetch current technician.");
+    }
+    util::Map<std::string, JobCard*> currentAssignedJobs = getJobCards(currentTechnician->getId());
+    if (currentAssignedJobs.getSize() == 0)
+    {
+        throw std::runtime_error("No job cards assigned to the technician.");
+    }
+    auto& trackedJobCards = m_dataStore.getJobCards();
+    auto& trackedServiceBookings = m_dataStore.getServiceBookings();
+    if (currentAssignedJobs.find(jobID) != -1)
+    {
+        int jobIndex = trackedJobCards.find(jobID);
+        if (jobIndex == -1)
+        {
+            throw std::runtime_error("Unable to fetch current job.");
+        }
+        auto& trackedCurrentJob = trackedJobCards.getValueAt(jobIndex);
+        JobCard* currentJob = trackedCurrentJob.data;
+        if (currentJob == nullptr)
+        {
+            throw std::runtime_error("Unable to fetch current job.");
+        }
+        if (currentJob->getStatus() == util::ServiceJobStatus::STARTED)
+        {
+            currentJob->setStatus(util::ServiceJobStatus::IN_PROGRESS);
+            trackedCurrentJob.state = RecordState::MODIFIED;
+            jobStatusUpdated = true;
+        }
         else if (currentJob->getStatus() == util::ServiceJobStatus::IN_PROGRESS)
         {
             currentJob->setStatus(util::ServiceJobStatus::COMPLETED);
+            trackedCurrentJob.state = RecordState::MODIFIED;
             jobStatusUpdated = true;
             serviceBookingCompleted = hasCompletedAllJobs(currentJob->getBookingId(), currentAssignedJobs);
             if (serviceBookingCompleted)
             {
+                const std::string& bookingId = currentJob->getBookingId();
                 currentJob->getBooking()->setStatus(util::ServiceJobStatus::COMPLETED);
+                trackedServiceBookings.getValueAt(trackedServiceBookings.find(bookingId)).state = RecordState::MODIFIED;
                 paymentManagementService.generateInvoice(currentJob->getBooking());
-                std::string title = "Service Booking completed. Invoice Generated.";
-                std::string message = "Services completed for the booking and invoice generated.";
+                std::string title = "Service Booking Completed";
+                std::string message = "Service Booking (ID: " + bookingId + ") has been completed successfully. An invoice has been generated.";
                 sendNotification(currentJob->getBooking()->getCustomer(), title, message);
             }
         }
-	}
-	else
-	{
-		throw std::runtime_error("Failed to update job status. Job may already be completed.");
-	}
-	if (!jobStatusUpdated)
-	{
-		throw std::runtime_error("Failed to update job status. Job may already be completed.");
-	}
+    }
+    else
+    {
+        throw std::runtime_error("Failed to update job status. Job may already be completed.");
+    }
+    if (!jobStatusUpdated)
+    {
+        throw std::runtime_error("Failed to update job status. Job may already be completed.");
+    }
+    m_dataStore.saveJobCards();
+    m_dataStore.saveServiceBookings();
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/ServiceManagementService.h

@@ -35,6 +35,7 @@ public:
     void createJobCard(const std::string& bookingID, const std::string& technicianID, const std::string& serviceID);
     void createService(const std::string& name, const util::Vector<std::string>& inventoryItemIDs, double laborCost);
     void removeService(const std::string& serviceID);
+    void removeServiceBooking(const std::string& bookingID);
     util::Map<std::string, JobCard*> getJobCards(const std::string& technicianID);
     void updateJobStatus(const std::string& jobID);
     void cancelCustomerServiceBookings(const std::string& customerID);

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/UserManagementService.cpp

@@ -15,6 +15,7 @@ Date:19-May-2026
 #include "Notification.h"
 #include "PaymentManagementService.h"
 #include "ServiceManagementService.h"
+#include "AuthenticationManagementService.h"
 #include "User.h"
 #include "UserManagementService.h"
 #include "Vector.h"
@@ -22,6 +23,7 @@ Date:19-May-2026
 #include "Utility.h"
 #include "TrackedRecord.h"
 #include "DataStoreLockGuard.h"
+#include "EventManager.h"
 
 /*
 Function: ensureAdminExists
@@ -113,6 +115,7 @@ Return type: void
 */
 void UserManagementService::updateUserDetails(const std::string& userID, const std::string& email, const std::string& phone)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	DataStoreLockGuard lock(m_dataStore);
 	auto& trackedUsersMap = m_dataStore.getUsers();
 	auto usersMap = util::getObjects(trackedUsersMap);
@@ -160,6 +163,7 @@ Throws:
 */
 util::Vector<Notification*> UserManagementService::getUserNotifications(const std::string& userID)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	DataStoreLockGuard lock(m_dataStore);
 	auto& trackedUsersMap = m_dataStore.getUsers(); 
 	if (trackedUsersMap.find(userID) == -1)
@@ -203,6 +207,7 @@ Throws:
 */
 void UserManagementService::deleteNotification(const std::string& notificationID, const std::string& userID)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	DataStoreLockGuard lock(m_dataStore);
 	auto& trackedUsersMap = m_dataStore.getUsers();
 	auto& trackedNotificationsMap = m_dataStore.getNotifications();
@@ -264,33 +269,42 @@ Return type: void
 */
 void UserManagementService::removeUser(const std::string& userID)
 {
+    AuthenticationManagementService::ensureAuthorization();
 	InventoryManagementService inventoryManagementService;
 	PaymentManagementService paymentManagementService;
 	ServiceManagementService serviceManagementService;
-	DataStoreLockGuard lock(m_dataStore);
-	auto& trackedUsersMap = m_dataStore.getUsers();
-	int index = trackedUsersMap.find(userID);
-	if (index != -1)
+	std::string removedUserID;
 	{
-		User* user = trackedUsersMap.getValueAt(index).data;
-		if (user != nullptr)
+		DataStoreLockGuard lock(m_dataStore);
+		auto& trackedUsersMap = m_dataStore.getUsers();
+		int index = trackedUsersMap.find(userID);
+		if (index != -1)
 		{
-			if (user->getUserType() == util::UserType::CUSTOMER)
+			User* user = trackedUsersMap.getValueAt(index).data;
+			if (user != nullptr)
 			{
-				serviceManagementService.cancelCustomerServiceBookings(userID);
+				if (user->getUserType() == util::UserType::CUSTOMER)
+				{
+					serviceManagementService.cancelCustomerServiceBookings(userID);
+				}
+				if (user->getUserType() == util::UserType::TECHNICIAN)
+				{
+					serviceManagementService.cancelTechnicianJobs(userID);
+				}
+				inventoryManagementService.detach(user);
+				paymentManagementService.detach(user);
+				serviceManagementService.detach(user);
+				user->setState(util::State::INACTIVE);
+				trackedUsersMap.getValueAt(index).state = RecordState::MODIFIED;
+				removedUserID = user->getId();
+				m_dataStore.saveUsers();
 			}
-			if (user->getUserType() == util::UserType::TECHNICIAN)
-			{
-				serviceManagementService.cancelTechnicianJobs(userID);
-			}
-			inventoryManagementService.detach(user);
-			paymentManagementService.detach(user);
-			serviceManagementService.detach(user);
-			user->setState(util::State::INACTIVE);
-			trackedUsersMap.getValueAt(index).state = RecordState::MODIFIED;
-			m_dataStore.saveUsers();
 		}
 	}
+	if (!removedUserID.empty())
+	{
+		EventManager::sendUserDisabledEvent(removedUserID);
+	}
 }
 
 /*

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/AdminMenu.cpp

@@ -30,10 +30,16 @@ Return type: void
 */
 void AdminMenu::showMenu()
 {
+	startEventListener();
     while (true)
     {
         try
         {
+			if (!m_isMenuActive)
+			{
+				logout();
+				break;
+			}
             int choice;
             util::clear();
             std::cout << "Admin Menu"
@@ -68,6 +74,7 @@ void AdminMenu::showMenu()
             util::pressEnter();
         }
     }
+	stopEventListener();
 }
 
 /*
@@ -78,6 +85,11 @@ Return type: bool - true if menu continues, false if logout
 */
 bool AdminMenu::handleOperation(int choice)
 {
+	if (!m_isMenuActive)
+	{
+		logout();
+		return false;
+	}
     switch (choice)
     {
     case 1:
@@ -141,6 +153,25 @@ bool AdminMenu::handleOperation(int choice)
     return true;
 }
 
+/*
+Function: handleNotificationEvent
+Description: Retrieves and displays the latest notification for the
+			 currently logged in admin.
+Parameter: None
+Return type: void
+*/
+void AdminMenu::handleNotificationEvent()
+{
+	auto notifications = m_controller.getNotifications();
+	const User* authenticatedUser = m_controller.getAuthenticatedUser();
+	std::string name;
+	if (authenticatedUser)
+	{
+		name = authenticatedUser->getName();
+	}
+	displayNewNotification(notifications, name);
+}
+
 /*
 Function: logout
 Description: Logs out the currently authenticated admin user.
@@ -307,6 +338,23 @@ void AdminMenu::removeInventoryItem()
             std::string selectedItemId = selectedItem->getId();
             m_controller.removeInventoryItem(selectedItemId);
             std::cout << "Item " << selectedItem->getPartName() << " removed successfully." << std::endl;
+			const util::Map<std::string, const Service*>& listOfService = m_controller.getServices();
+			for (int serviceIndex = 0; serviceIndex < listOfService.getSize(); serviceIndex++)
+			{
+				const Service* service = listOfService.getValueAt(serviceIndex);
+				if (!service)
+				{
+					continue;
+				}
+				const util::Map<std::string, InventoryItem*>& requiredItems = service->getRequiredInventoryItems();
+				if (requiredItems.find(selectedItemId) != -1) 
+				{
+					m_controller.removeService(service->getId()); 
+					std::cout << "Service " << service->getName()
+						<< " removed as the item "
+						<< selectedItem->getPartName() << " required for the service has been removed." << std::endl;
+				}
+			}
         }
     }
     util::pressEnter();

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/AdminMenu.h

@@ -9,12 +9,13 @@ Date:19-May-2026
 
 #pragma once
 #include "Controller.h"
+#include "Menu.h"
 
-class AdminMenu
+class AdminMenu : public Menu
 {
 private:
-    Controller m_controller;
     bool handleOperation(int choice);
+    void handleNotificationEvent() override;
 public:
     void showMenu();
     void logout();

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/CustomerMenu.cpp

@@ -32,10 +32,17 @@ Return type: void
 */
 void CustomerMenu::showMenu()
 {
+
+    startEventListener();
     while (true)
     {
         try
         {
+            if (!m_isMenuActive)
+            {
+                logout();
+                break;
+            }
             int choice;
             util::clear();
             std::cout << "Customer Menu"
@@ -44,11 +51,12 @@ void CustomerMenu::showMenu()
                 << "\n3. Update Profile"
                 << "\n4. Change Password"
                 << "\n5. View Service History"
-                << "\n6. Complete Payments"
-                << "\n7. View Invoices"
-                << "\n8. View Notifications"
-                << "\n9. Configure Notifications"
-                << "\n10. Logout"
+                << "\n6. Cancel Service Booking"
+                << "\n7. Complete Payments"
+                << "\n8. View Invoices"
+                << "\n9. View Notifications"
+                << "\n10. Configure Notifications"
+                << "\n11. Logout"
                 << "\nEnter a choice: ";
             util::read(choice);
             if (!handleOperation(choice))
@@ -62,6 +70,7 @@ void CustomerMenu::showMenu()
             util::pressEnter();
         }
     }
+    stopEventListener();
 }
 
 /*
@@ -72,6 +81,11 @@ Return type: bool - true if menu continues, false if logout
 */
 bool CustomerMenu::handleOperation(int choice)
 {
+    if (!m_isMenuActive)
+    {
+        logout();
+        return false;
+    }
     switch (choice)
     {
     case 1:
@@ -90,18 +104,21 @@ bool CustomerMenu::handleOperation(int choice)
         viewServiceHistory();
         break;
     case 6:
-        completePayments();
+        cancelServiceBooking();
         break;
     case 7:
-        viewInvoices();
+        completePayments();
         break;
     case 8:
-        viewNotifications();
+        viewInvoices();
         break;
     case 9:
-        configureNotifications();
+        viewNotifications();
         break;
     case 10:
+        configureNotifications();
+        break;
+    case 11:
         logout();
         return false;
     default:
@@ -111,6 +128,25 @@ bool CustomerMenu::handleOperation(int choice)
     return true;
 }
 
+/*
+Function: handleNotificationEvent
+Description: Retrieves and displays the latest notification for the
+             currently logged in admin.
+Parameter: None
+Return type: void
+*/
+void CustomerMenu::handleNotificationEvent()
+{
+    auto notifications = m_controller.getNotifications();
+    const User* authenticatedUser = m_controller.getAuthenticatedUser();
+    std::string name;
+    if (authenticatedUser)
+    {
+        name = authenticatedUser->getName();
+    }
+    displayNewNotification(notifications, name);
+}
+
 /*
 Function: logout
 Description: Logs out the currently authenticated customer user.
@@ -184,6 +220,13 @@ void CustomerMenu::selectService()
         util::pressEnter();
         return;
     }
+    if (!verifyAllPaymentsCompleted(m_controller))
+    {
+        std::cout << "Your booking cannot be processed because you have pending payments for previous services. Please complete all outstanding invoices before booking a new service."
+             << std::endl;
+        util::pressEnter();
+        return;
+    }
     util::Vector<std::string> selectedServices;
     const Service* selectedService = selectServiceFromServices(services);
     if (selectedService == nullptr)
@@ -226,6 +269,13 @@ void CustomerMenu::selectComboPackage()
         util::pressEnter();
         return;
     }
+    if (!verifyAllPaymentsCompleted(m_controller))
+    {
+        std::cout << "Your booking cannot be processed because you have pending payments for previous services. Please complete all outstanding invoices before booking a new combo package."
+            << std::endl;
+        util::pressEnter();
+        return;
+    }
     const ComboPackage* selectedComboPackage = selectComboPackageFromPackages(activeComboPackages);
     if (selectedComboPackage == nullptr)
     {
@@ -301,6 +351,46 @@ void CustomerMenu::viewServiceHistory()
     util::pressEnter();
 }
 
+/*
+Function: cancelServiceBooking
+Description: Allows the customer to cancel a pending service booking.
+             Displays the list of active bookings, lets the user select one,
+             and removes it from the system. If no bookings are available,
+             an appropriate message is shown.
+Parameter: None
+Return type: void
+*/
+void CustomerMenu::cancelServiceBooking()
+{
+    util::clear();
+    std::cout << "Cancel Service Booking\n";
+    const User* currentUser = m_controller.getAuthenticatedUser();
+    std::string currentUserID = currentUser->getId();
+    util::Map<std::string, const ServiceBooking*> serviceBookingsByCurrentUser = m_controller.getServiceBookingsByUser(currentUserID);
+    util::Map<int, const ServiceBooking*> serviceBookingsMap;
+    auto currentPendingServiceBookings = filterActiveServiceBookings(serviceBookingsByCurrentUser);
+    int bookingsSize = currentPendingServiceBookings.getSize();
+    if (listServiceBookings(currentPendingServiceBookings, bookingsSize, serviceBookingsMap))
+    {
+        const ServiceBooking* selectedService = selectPendingServiceBookings(serviceBookingsMap);
+        if (selectedService)
+        {
+            m_controller.removeServiceBooking(selectedService->getId());
+            std::cout << "Cancelled Service booking of id " + selectedService->getId() << std::endl << std::endl;
+        }
+        else
+        {
+            std::cout << "Invalid service booking index.\n\n";
+            return;
+        }
+    }
+    else
+    {
+        std::cout << "No pending service bookings available.\n\n";
+    }
+    util::pressEnter();
+}
+
 /*
 Function: completePayments
 Description: Allows the customer to complete pending payments for invoices.

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/CustomerMenu.h

@@ -9,13 +9,14 @@ Date:19-May-2026
 */
 
 #pragma once
+#include "Menu.h"
 #include "Controller.h"
 
-class CustomerMenu
+class CustomerMenu : public Menu
 {
 private:
-    Controller m_controller;
     bool handleOperation(int choice);
+    void handleNotificationEvent();
 public:
     void showMenu();
     void logout();
@@ -27,5 +28,6 @@ public:
     void completePayments();
     void viewInvoices();
     void viewNotifications();
+    void cancelServiceBooking();
     void configureNotifications();
-};
+};

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/Menu.cpp

@@ -0,0 +1,150 @@
+/*
+File: Menu.cpp
+Description: Implementation file containing common menu event listener
+             functionality, account disable handling, and notification
+             event dispatching for all menu types.
+Author: Trenser
+Date:16-Jun-2026
+*/
+
+#include "Menu.h"
+
+/*
+Function: Menu
+Description: Constructs a Menu object and initializes event handles
+             and menu state.
+Parameter: None
+Return type: None
+*/
+Menu::Menu()
+    :
+    m_isMenuActive(false),
+    m_accountDisabledEvent(NULL),
+    m_notificationAvailableEvent(NULL),
+    m_shutdownEvent(NULL) {}
+
+/*
+Function: ~Menu
+Description: Destroys the Menu object and performs event listener
+             cleanup.
+Parameter: None
+Return type: None
+*/
+Menu::~Menu()
+{
+    stopEventListener();
+}
+
+/*
+Function: startEventListener
+Description: Creates menu event handles, registers them with the
+             authentication service, and starts the event listener
+             thread.
+Parameter: None
+Return type: void
+*/
+void Menu::startEventListener()
+{
+    if (m_isMenuActive.load())
+    {
+        return;
+    }
+    m_isMenuActive.store(true);
+    m_accountDisabledEvent = CreateEventA(NULL, FALSE, FALSE, NULL);
+    m_notificationAvailableEvent = CreateEventA(NULL, FALSE, FALSE, NULL);
+    m_shutdownEvent = CreateEventA(NULL, FALSE, FALSE, NULL);
+    m_controller.registerEvents(m_accountDisabledEvent, m_notificationAvailableEvent);
+    m_eventListenerThread = std::thread(&Menu::eventListenerLoop, this);
+}
+
+/*
+Function: eventListenerLoop
+Description: Waits for account disabled, notification available,
+             and shutdown events and dispatches them to the
+             appropriate handlers.
+Parameter: None
+Return type: void
+*/
+void Menu::eventListenerLoop()
+{
+    HANDLE handles[3] = { NULL, NULL, NULL };
+    handles[0] = m_accountDisabledEvent;
+    handles[1] = m_notificationAvailableEvent;
+    handles[2] = m_shutdownEvent;
+    while (m_isMenuActive.load())
+    {
+        DWORD result = WaitForMultipleObjects(3, handles, FALSE, INFINITE);
+        switch (result)
+        {
+        case WAIT_OBJECT_0:
+            handleAccountDisabledEvent();
+            break;
+        case WAIT_OBJECT_0 + 1:
+            handleNotificationEvent();
+            break;
+        case WAIT_OBJECT_0 + 2:
+            return;
+        }
+    }
+}
+
+/*
+Function: stopEventListener
+Description: Stops the event listener thread and releases all
+             associated event handles.
+Parameter: None
+Return type: void
+*/
+void Menu::stopEventListener()
+{
+    m_isMenuActive.store(false);
+    if (m_shutdownEvent)
+    {
+        SetEvent(m_shutdownEvent);
+    }
+    if (m_eventListenerThread.joinable())
+    {
+        m_eventListenerThread.join();
+    }
+    if (m_accountDisabledEvent)
+    {
+        CloseHandle(m_accountDisabledEvent);
+    }
+    if (m_notificationAvailableEvent)
+    {
+        CloseHandle(m_notificationAvailableEvent);
+    }
+    if (m_shutdownEvent)
+    {
+        CloseHandle(m_shutdownEvent);
+    }
+    m_accountDisabledEvent = NULL;
+    m_notificationAvailableEvent = NULL;
+    m_shutdownEvent = NULL;
+}
+
+/*
+Function: handleAccountDisabledEvent
+Description: Handles an account disabled event by marking the menu
+             inactive and notifying the user.
+Parameter: None
+Return type: void
+*/
+void Menu::handleAccountDisabledEvent()
+{
+    m_isMenuActive.store(false);
+    const User* authenticatedUser = m_controller.getAuthenticatedUser();
+    std::string messageTitle = "Account Disabled";
+    if (authenticatedUser)
+    {
+        messageTitle += " - " + authenticatedUser->getName();
+    }
+    MessageBoxA(
+        GetConsoleWindow(),
+        "Your account has been disabled.",
+        messageTitle.c_str(),
+        MB_OK |
+        MB_ICONWARNING |
+        MB_SETFOREGROUND |
+        MB_TOPMOST);
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/Menu.h

@@ -0,0 +1,33 @@
+/*
+File: Menu.h
+Description: Base class providing common event listener functionality
+             for all menu implementations.
+Author: Trenser
+Date:16-Jun-2026
+*/
+
+#pragma once
+
+#include <windows.h>
+#include <atomic>
+#include <thread>
+#include "Controller.h"
+
+class Menu
+{
+protected:
+    Controller m_controller;
+    std::atomic<bool> m_isMenuActive;
+    HANDLE m_accountDisabledEvent;
+    HANDLE m_notificationAvailableEvent;
+    HANDLE m_shutdownEvent;
+    std::thread m_eventListenerThread;
+    void startEventListener();
+    void stopEventListener();
+    void eventListenerLoop();
+    void handleAccountDisabledEvent();
+    virtual void handleNotificationEvent() = 0;
+public:
+    Menu();
+    virtual ~Menu();
+};

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/MenuHelper.h

@@ -28,6 +28,7 @@ Date: 21-May-2026
 #include "Utility.h"
 #include "Validator.h"
 #include "Vector.h"
+#include "StringHelper.h"
 
 /*
 Function: displayAllServices
@@ -587,7 +588,7 @@ inline void displayInvoices(util::Map<std::string, const Invoice*> currentUserIn
                     << util::getPaymentStatusString(selectedInvoice->getStatus()) << std::endl;
                 std::cout << std::left << std::setw(20) << "Payment Mode:"
                     << util::getPaymentModeString(selectedInvoice->getPaymentMethod()) << std::endl;
-                auto inventoryItemsInInvoice = selectedInvoice->getParts();
+                auto& inventoryItemsInInvoice = selectedInvoice->getParts();
                 if (inventoryItemsInInvoice.isEmpty())
                 {
                     std::cout << "No inventory items used.\n\n";
@@ -596,7 +597,6 @@ inline void displayInvoices(util::Map<std::string, const Invoice*> currentUserIn
                 std::cout << "\nItems Used:\n";
                 std::cout << std::left
                     << std::setw(20) << "ItemName"
-                    << std::setw(10) << "Quantity"
                     << std::setw(10) << "Price"
                     << std::endl;
                 std::cout << std::string(40, '-') << std::endl;
@@ -605,7 +605,6 @@ inline void displayInvoices(util::Map<std::string, const Invoice*> currentUserIn
                     InventoryItem* currentItem = inventoryItemsInInvoice.getValueAt(iterator);
                     std::cout << std::left
                         << std::setw(20) << currentItem->getPartName()
-                        << std::setw(10) << currentItem->getQuantity()
                         << std::setw(10) << currentItem->getPrice()
                         << std::endl;
                 }
@@ -1056,6 +1055,21 @@ inline const Service* selectServiceFromServices(const util::Map<std::string, con
         {
             continue;
         }
+        bool hasDepletedItem = false;
+        const util::Map<std::string, InventoryItem*>& requiredItems = currentService->getRequiredInventoryItems();
+        for (int itemIndex = 0; itemIndex < requiredItems.getSize(); itemIndex++)
+        {
+            const InventoryItem* item = requiredItems.getValueAt(itemIndex);
+            if (!item || item->getQuantity() < 1)
+            {
+                hasDepletedItem = true;
+                break;
+            }
+        }
+        if (hasDepletedItem)
+        {
+            continue; 
+        }
         activeServicesMap.insert(currentIndex, currentService);
         double partsCost = util::calculatePartsCost(currentService);
         std::cout << std::left
@@ -1130,15 +1144,18 @@ inline void displayAllComboPackages(util::Map<std::string, const ComboPackage*>
     for (int index = 0; index < comboPackages.getSize(); index++)
     {
         const ComboPackage* currentComboPackage = comboPackages.getValueAt(index);
-        if (currentComboPackage && currentComboPackage->getState() != util::State::ACTIVE)
+        if (currentComboPackage) 
         {
-            continue;
+            if (currentComboPackage->getState() != util::State::ACTIVE)
+            {
+                continue;
+            }
+            std::cout << std::left
+                << std::setw(15) << currentComboPackage->getId()
+                << std::setw(35) << util::truncateString(currentComboPackage->getPackageName(), 30)
+                << std::setw(15) << util::calculateComboServiceEstimatedCost(currentComboPackage)
+                << std::endl;
         }
-        std::cout << std::left
-            << std::setw(15) << currentComboPackage->getId()
-            << std::setw(35) << util::truncateString(currentComboPackage->getPackageName(), 30)
-            << std::setw(15) << util::calculateComboServiceEstimatedCost(currentComboPackage)
-            << std::endl;
     }
 }
 
@@ -1164,18 +1181,21 @@ inline const ComboPackage* selectComboPackageFromPackages(const util::Map<std::s
     for (int index = 0; index < comboPackages.getSize(); index++)
     {
         const ComboPackage* currentComboPackage = comboPackages.getValueAt(index);
-        if (currentComboPackage && currentComboPackage->getState() != util::State::ACTIVE)
+        if (currentComboPackage)
         {
-            continue;
+            if (currentComboPackage->getState() != util::State::ACTIVE)
+            {
+                continue;
+            }
+            activeComboPackages.insert(currentIndex, currentComboPackage);
+            std::cout << std::left
+                << std::setw(10) << currentIndex
+                << std::setw(15) << currentComboPackage->getId()
+                << std::setw(35) << util::truncateString(currentComboPackage->getPackageName(), 30)
+                << std::setw(15) << util::calculateComboServiceEstimatedCost(currentComboPackage)
+                << std::endl;
+            currentIndex++;
         }
-        activeComboPackages.insert(currentIndex, currentComboPackage);
-        std::cout << std::left
-            << std::setw(10) << currentIndex
-            << std::setw(15) << currentComboPackage->getId()
-            << std::setw(35) << util::truncateString(currentComboPackage->getPackageName(), 30)
-            << std::setw(15) << util::calculateComboServiceEstimatedCost(currentComboPackage)
-            << std::endl;
-        currentIndex++;
     }
     if (activeComboPackages.getSize() == 0)
     {
@@ -1407,4 +1427,89 @@ inline std::string selectComboPackage(util::Map<std::string, const ComboPackage*
         std::cout << "Enter a valid choice.\n";
         return "";
     }
-}
+}
+
+/*
+Function: displayNewNotification
+Description: Displays the most recent notification from the supplied
+             notification collection.
+Parameter: util::Vector<const Notification*> notifications -
+           collection of notifications
+           const std::string& - The name of the user currently authenticated with the system
+Return type: void
+*/
+inline void displayNewNotification(util::Vector<const Notification*> notifications, const std::string& name)
+{
+    const Notification* notification = nullptr;
+	size_t numberOfNotifications = notifications.getSize();
+	for (int index = 0; index < numberOfNotifications; index++)
+	{
+		if (!notification)
+		{
+			notification = notifications[index];
+		}
+		else
+		{
+            if (util::extractNumber(notification->getId()) < util::extractNumber(notifications[index]->getId()))
+			{
+				notification = notifications[index];
+			}
+		}
+	}
+    if (notification)
+    {
+        std::string messageTitle = notification->getTitle();
+        if (!name.empty())
+        {
+            messageTitle += " - " + name;
+        }
+        MessageBoxA(
+            GetConsoleWindow(),
+            notification->getMessage().c_str(),
+            messageTitle.c_str(),
+            MB_OK |
+            MB_ICONINFORMATION);
+    }
+}
+
+/*
+Function: verifyAllPaymentsCompleted
+Description: Checks whether the authenticated customer has completed
+             all payments for their invoices. Iterates through all
+             invoices belonging to the customer and verifies that
+             each invoice has a payment status of COMPLETED.
+Parameters: Controller& m_controller -
+            reference to the Controller object used to access
+            authenticated user and invoice data
+Return type: bool
+             true if all invoices for the authenticated customer
+             are completed, false if any invoice is pending or not completed
+Throws: std::runtime_error if no authenticated user is found
+*/
+inline bool verifyAllPaymentsCompleted(Controller& m_controller)
+{
+    const User* authenticatedUser = m_controller.getAuthenticatedUser();
+    if (!authenticatedUser)
+    {
+        throw std::runtime_error("No authenticated user found.");
+    }
+    const std::string& authenticatedUserId = authenticatedUser->getId();
+    util::Map<std::string, const Invoice*> listOfInvoices = m_controller.getAllInvoices();
+    for (int invoiceIndex = 0; invoiceIndex < listOfInvoices.getSize(); ++invoiceIndex)
+    {
+        const Invoice* invoice = listOfInvoices.getValueAt(invoiceIndex);
+        if (!invoice)
+        {
+            continue;
+        }
+        const std::string& customerId = invoice->getBooking()->getCustomerId();
+        if (customerId == authenticatedUserId)
+        {
+            if (invoice->getStatus() != util::PaymentStatus::COMPLETED)
+            {
+                return false;
+            }
+        }
+    }
+    return true;
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/TechnicianMenu.cpp

@@ -27,10 +27,16 @@ Returns:
 */
 void TechnicianMenu::showMenu()
 {
+    startEventListener();
     while (true)
     {
         try
         {
+            if (!m_isMenuActive)
+            {
+                logout();
+                break;
+            }
             int choice;
             util::clear();
             std::cout << "Technician Menu"
@@ -52,6 +58,7 @@ void TechnicianMenu::showMenu()
             util::pressEnter();
         }
     }
+    stopEventListener();
 }
 
 /*
@@ -62,6 +69,11 @@ Return type: bool - true if menu continues, false if logout
 */
 bool TechnicianMenu::handleOperation(int choice)
 {
+    if (!m_isMenuActive)
+    {
+        logout();
+        return false;
+    }
     switch (choice)
     {
     case 1:
@@ -86,6 +98,25 @@ bool TechnicianMenu::handleOperation(int choice)
     return true;
 }
 
+/*
+Function: handleNotificationEvent
+Description: Retrieves and displays the latest notification for the
+             currently logged in admin.
+Parameter: None
+Return type: void
+*/
+void TechnicianMenu::handleNotificationEvent()
+{
+    auto notifications = m_controller.getNotifications();
+    const User* authenticatedUser = m_controller.getAuthenticatedUser();
+    std::string name;
+    if (authenticatedUser)
+    {
+        name = authenticatedUser->getName();
+    }
+    displayNewNotification(notifications, name);
+}
+
 /*
 Function: displayJobs
 Description: Displays all Jobs assigned to a Technician

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/TechnicianMenu.h

@@ -9,12 +9,13 @@ Date:19-May-2026
 
 #pragma once
 #include "Controller.h"
+#include "Menu.h"
 
-class TechnicianMenu
+class TechnicianMenu : public Menu
 {
 private:
-    Controller m_controller;
     bool handleOperation(int choice);
+    void handleNotificationEvent();
 public:
     void showMenu();
     void displayJobs();