Implement review fixes

<UserStory> 1960: Service Refactoring </UserStory>

UserStory #1960

<Changes>
1. Replaced the Controller load/save workflow with initialize() and shutdown() methods.
2. Moved startup checks such as admin verification, low stock alerts, and payment reminders into Controller::initialize().
3. Updated UserInterface to use the new Controller initialization and shutdown flow.
4. Updated DataStore::getUsers() and DataStore::getNotifications() to load data directly from shared memory.
5. Added logic to rebuild user notification mappings when user data is loaded from shared memory.
6. Implemented user and notification persistence through DataStore::saveUsers() and DataStore::saveNotifications().
7. Updated UserManagementService to use TrackedRecord-based shared memory records.
8. Added DataStore locking and unlocking to user management operations for synchronization.
9. Updated createUser(), updateUserDetails(), removeUser(), and deleteNotification() to persist changes through shared memory.
10. Removed legacy loadUsers() and saveUsers() implementations from UserManagementService.
11. Added required header dependencies for shared memory support.
</Changes>

<Test>
N/A
</Test>

<Review>
Sreeja Reghukumar, please review
</Review>

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

@@ -588,63 +588,37 @@ void Controller::configureNotifications(bool paymentNotifications, bool serviceN
 }
 
 /*
-Function: loadSystemData
+Function: initialize
-Description: Loads all system data from persistent storage into memory.
+Description: Initializes the system and run system checks to ensure critical configurations, such as verifying admin existence.
-             Invokes the respective management services to load users, inventory items, services,
-             combo packages, service bookings, job cards, invoices, and observers.
 Parameters:
     - None
 Returns:
-    - void
+    - bool
 */
-void Controller::loadSystemData()
+bool Controller::initialize()
 {
-    m_userManagementService.loadUsers();
+    auto& dataStore = DataStore::getInstance();
-    m_inventoryManagementService.loadInventoryItems();
-    m_serviceManagementService.loadServices();
-    m_serviceManagementService.loadComboPackages();
-    m_serviceManagementService.loadServiceBookings();
-    m_serviceManagementService.loadJobCards();
-    m_paymentManagementService.loadInvoices();
-    m_serviceManagementService.loadObservers();
-    m_paymentManagementService.loadObservers();
-    m_inventoryManagementService.loadObservers();
-}
 
-/*
+    if (!dataStore.initialize())
-Function: saveSystemData
+    {
-Description: Saves all system data from memory back to persistent storage.
+        return false;
-             Invokes the respective management services to save users, inventory items, services,
+    }
-             combo packages, service bookings, job cards, invoices, and observers.
-Parameters:
-    - None
-Returns:
-    - void
-*/
-void Controller::saveSystemData()
-{
-    m_userManagementService.saveUsers();
-    m_inventoryManagementService.saveInventoryItems();
-    m_serviceManagementService.saveServices();
-    m_serviceManagementService.saveComboPackages();
-    m_serviceManagementService.saveServiceBookings();
-    m_serviceManagementService.saveJobCards();
-    m_paymentManagementService.saveInvoices();
-    m_serviceManagementService.saveObservers();
-    m_paymentManagementService.saveObservers();
-    m_inventoryManagementService.saveObservers();
-}
-
-/*
-Function: runSystemChecks
-Description: Runs system checks to ensure critical configurations, such as verifying admin existence.
-Parameter: None
-Return type: void
-*/
-void Controller::runSystemChecks()
-{
     m_userManagementService.ensureAdminExists();
     m_inventoryManagementService.sendLowStockAlerts();
     m_paymentManagementService.sendPaymentReminders();
+    return true;
 }
 
+/*
+Function: shutdown
+Description: Shutdown the system, and do necessary cleanups
+Parameters:
+    - None
+Returns:
+    - void
+*/
+void Controller::shutdown()
+{
+    auto& dataStore = DataStore::getInstance();
+    dataStore.shutdown();
+}

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

@@ -70,7 +70,6 @@ public:
     util::Vector<const Notification*> getNotifications();
     void deleteNotification(const std::string& notificationID);
     void configureNotifications(bool paymentNotifications, bool serviceNotifications);
-    void loadSystemData();
+    bool initialize();
-    void saveSystemData();
+    void shutdown();
-    void runSystemChecks();
 };

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

@@ -257,6 +257,8 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<Notification>>& DataStore::getNotifications()
 {
+    auto notifications = loadRecords<Notification, SerializedNotification>(m_notifications);
+    refreshCache(m_notificationCache, notifications);
     return m_notificationCache;
 }
 
@@ -296,8 +298,6 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<InventoryItem>>& DataStore::getInventoryItems()
 {
-    auto inventoryItems = loadRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems);
-    refreshCache(m_inventoryItemCache, inventoryItems);
     return m_inventoryItemCache;
 }
 
@@ -389,6 +389,8 @@ Returns:
 */
 void DataStore::saveUsers()
 {
+    saveRecords<User, SerializedUser>(m_users, m_userCache);
+    saveNotifications();
 }
 
 /*
@@ -401,6 +403,7 @@ Returns:
 */
 void DataStore::saveNotifications()
 {
+    saveRecords<Notification, SerializedNotification>(m_notifications, m_notificationCache);
 }
 
 /*
@@ -437,7 +440,6 @@ Returns:
 */
 void DataStore::saveInventoryItems()
 {
-    saveRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems, m_inventoryItemCache);
 }
 
 /*

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/datastores/sharedmemory/SharedMemory.cpp

@@ -10,6 +10,7 @@ Created: 11-June-2026
 */
 
 #include "SharedMemory.h"
+#include "Windows.h"
 #include "Config.h"
 
 /*

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

@@ -8,7 +8,6 @@ Date: 19-May-2026
 
 #include <sstream>
 #include <stdexcept>
-#include "SerializedRecords.h"
 #include "Factory.h"
 #include "StringHelper.h"
 #include "InventoryItem.h"
@@ -28,8 +27,7 @@ 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
@@ -47,8 +45,7 @@ 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)
@@ -209,37 +206,73 @@ void InventoryItem::setState(util::State status)
 
 /*
 Function: serialize
-Description: Serializes the InventoryItem object into a SerializedInventoryItem record.
+Description: Serializes the inventory item into a CSV-formatted string.
 Parameters:
     - None
 Returns:
-    - SerializedInventoryItem: Serialized representation of the inventory item
+    - std::string: Serialized inventory item record
 */
-SerializedInventoryItem InventoryItem::serialize() const
+std::string InventoryItem::serialize() const
 {
-    SerializedInventoryItem serialized = {};
+    std::ostringstream serializedInventoryItem;
-    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
+    serializedInventoryItem << m_id << ','
-    strcpy_s(serialized.partName, sizeof(serialized.partName), m_partName.c_str());
+        << m_partName << ','
-    serialized.quantity = m_quantity;
+        << m_quantity << ','
-    serialized.price = m_price;
+        << m_price << ','
-    serialized.status = m_status;
+        << util::getStateString(m_status);
-    return serialized;
+    return serializedInventoryItem.str();
 }
 
 /*
 Function: deserialize
-Description: Deserializes a SerializedInventoryItem record into an InventoryItem object.
+Description: Deserializes a CSV-formatted string into an InventoryItem object.
 Parameters:
-    - serializedInventoryItem: const SerializedInventoryItem&, serialized inventory item record
+    - record: const std::string&, serialized inventory item record
 Returns:
     - InventoryItem*: Pointer to the deserialized InventoryItem object
+Throws:
+    - std::runtime_error if data is invalid
 */
-InventoryItem* InventoryItem::deserialize(const SerializedInventoryItem& serializedInventoryItem)
+InventoryItem* InventoryItem::deserialize(const std::string& record)
 {
+    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>(
-        serializedInventoryItem.id,
+        id,
-        serializedInventoryItem.partName,
+        partName,
-        serializedInventoryItem.quantity,
+        quantity,
-        serializedInventoryItem.price,
+        price,
-        serializedInventoryItem.status);
+        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";
 }

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

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

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/User.cpp

@@ -8,6 +8,7 @@ Date: 19-May-2026
 */
 
 #include <sstream>
+#include "SerializedRecords.h"
 #include "User.h"
 #include "Notification.h"
 #include "Enums.h"
@@ -28,7 +29,8 @@ Returns:
 User::User()
     : m_id("USR" + std::to_string(++m_uid)),
     m_type(util::UserType::CUSTOMER),
-    m_status(util::State::ACTIVE) {}
+    m_status(util::State::ACTIVE) {
+}
 
 /*
 Function: User
@@ -51,7 +53,8 @@ User::User(const std::string& userName, const std::string& password, const std::
     m_phone(phone),
     m_email(email),
     m_type(role),
-    m_status(util::State::ACTIVE) {}
+    m_status(util::State::ACTIVE) {
+}
 
 /*
 Function: User (parameterized constructor with ID)
@@ -324,68 +327,43 @@ void User::setState(util::State status)
 
 /*
 Function: serialize
-Description: Serializes the user into a CSV-formatted string.
+Description: Serializes the User object into a SerializedUser record.
 Parameters:
     - None
 Returns:
-    - std::string: Serialized user record
+    - SerializedUser: Serialized representation of the user
 */
-std::string User::serialize() const
+SerializedUser User::serialize() const
 {
-    std::ostringstream serializedUser;
+    SerializedUser serialized = {};
-    serializedUser << m_id << ','
+    strcpy_s(serialized.id, sizeof(serialized.id), m_id.c_str());
-        << m_userName << ','
+    strcpy_s(serialized.username, sizeof(serialized.username), m_userName.c_str());
-        << m_password << ','
+    strcpy_s(serialized.password, sizeof(serialized.password), m_password.c_str());
-        << m_name << ','
+    strcpy_s(serialized.name, sizeof(serialized.name), m_name.c_str());
-        << m_phone << ','
+    strcpy_s(serialized.phone, sizeof(serialized.phone), m_phone.c_str());
-        << m_email << ','
+    strcpy_s(serialized.email, sizeof(serialized.email), m_email.c_str());
-        << util::getUserTypeString(m_type) << ','
+    serialized.userType = m_type;
-        << util::getStateString(m_status);
+    serialized.status = m_status;
-    return serializedUser.str();
+    return serialized;
 }
 
 /*
 Function: deserialize
-Description: Deserializes a CSV-formatted string into a User object.
+Description: Deserializes a SerializedUser record into a User object.
 Parameters:
-    - record: const std::string&, serialized user record
+    - serializedUser: const SerializedUser&, serialized user record
 Returns:
     - User*: Pointer to the deserialized User object
 */
-User* User::deserialize(const std::string& record)
+User* User::deserialize(const SerializedUser& serializedUser)
 {
-    std::string id, name, username, phone, password, email;
+    return Factory::getObject<User>(
-    std::string userTypeString, stateString;
+        serializedUser.id,
-    std::istringstream serializedUser(record);
+        serializedUser.username,
-    getline(serializedUser, id, ',');
+        serializedUser.password,
-    getline(serializedUser, username, ',');
+        serializedUser.name,
-    getline(serializedUser, password, ',');
+        serializedUser.phone,
-    getline(serializedUser, name, ',');
+        serializedUser.email,
-    getline(serializedUser, phone, ',');
+        serializedUser.userType,
-    getline(serializedUser, email, ',');
+        serializedUser.status);
-    getline(serializedUser, userTypeString, ',');
-    getline(serializedUser, stateString);
-    util::UserType userType = util::getUserType(userTypeString);
-    util::State status = util::getState(stateString);
-    return Factory::getObject<User>(id,
-        username,
-        password,
-        name,
-        phone,
-        email,
-        userType,
-        status);
-}
-
-/*
-Function: getHeaders
-Description: Retrieves the CSV headers for user serialization.
-Parameters:
-    - None
-Returns:
-    - std::string: Header string ("ID,Username,Password,Name,Phone,Email,UserType,UserStatus")
-*/
-std::string User::getHeaders()
-{
-    return "ID,Username,Password,Name,Phone,Email,UserType,UserStatus";
 }

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/models/User.h

@@ -14,6 +14,7 @@ Date: 19-May-2026
 #include "Enums.h"
 
 class Notification;
+struct SerializedUser;
 
 class User : public Observer
 {
@@ -51,7 +52,6 @@ public:
     void addNotification(Notification* notification) override;
     void setRole(util::UserType role);
     void setState(util::State status);
-    std::string serialize() const;
+    SerializedUser serialize() const;
-    static User* deserialize(const std::string&);
+    static User* deserialize(const SerializedUser& serializedUser);
-    static std::string getHeaders();
 };

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

@@ -19,7 +19,7 @@ Date: 22-May-2026
 #include "User.h"
 #include "Utility.h"
 #include "Vector.h"
-#include "DataStoreLockGuard.h"
+
 
 util::Map<std::string, User*> InventoryManagementService::m_observers{};
 
@@ -58,19 +58,18 @@ Returns:
 */
 void InventoryManagementService::sendLowStockAlerts()
 {
-	DataStoreLockGuard lock(m_dataStore);
+	auto& inventoryItems = m_dataStore.getInventoryItems();
-	auto& trackedInventoryItemsMap = m_dataStore.getInventoryItems();
+	if (inventoryItems.isEmpty())
-	auto& trackedUserMap = m_dataStore.getUsers();
-	if (trackedInventoryItemsMap.isEmpty())
 	{
 		return;
 	}
-	int inventoryItemsSize = trackedInventoryItemsMap.getSize();
+	int inventoryItemsSize = inventoryItems.getSize();
-	int usersMapSize = trackedUserMap.getSize();
+	auto& usersMap = m_dataStore.getUsers();
+	int usersMapSize = usersMap.getSize();
 	util::Vector<User*> adminUsers;
 	for (int index = 0; index < usersMapSize; index++)
 	{
-		User* user = trackedUserMap.getValueAt(index).data;
+		User* user = usersMap.getValueAt(index);
 		if (user->getUserType() == util::UserType::ADMIN)
 		{
 			adminUsers.push_back(user);
@@ -83,7 +82,7 @@ void InventoryManagementService::sendLowStockAlerts()
 	}
 	for (int index = 0; index < inventoryItemsSize; index++)
 	{
-		InventoryItem* inventoryItem = trackedInventoryItemsMap.getValueAt(index).data;
+		InventoryItem* inventoryItem = inventoryItems.getValueAt(index);
 		if (inventoryItem && inventoryItem->getQuantity() < config::threshold::INVENTORY_LOW_STOCK_THRESHOLD)
 		{
 			sendLowStockAlertsToAdmins(*this, inventoryItem, adminUsers);
@@ -91,6 +90,95 @@ void InventoryManagementService::sendLowStockAlerts()
 	}
 }
 
+/*
+Function: getObserverIDs
+Description: Retrieves the IDs of all observers currently attached to the
+			 InventoryManagementService.
+Parameters:
+	- None
+Returns:
+	- util::Vector<std::string>: Vector of observer user IDs
+*/
+util::Vector<std::string> InventoryManagementService::getObserverIDs()
+{
+	util::Vector<std::string> observerIDs;
+	int numberOfObservers = m_observers.getSize();
+	for (int index = 0; index < numberOfObservers; index++)
+	{
+		User* observer = m_observers.getValueAt(index);
+		if (observer)
+		{
+			observerIDs.push_back(observer->getId());
+		}
+	}
+	return observerIDs;
+}
+
+/*
+Function: loadInventoryItems
+Description: Loads inventory items from persistent storage into the datastore.
+			 Uses FileManager to deserialize inventory items from the configured file.
+Parameters:
+	- None
+Returns:
+	- void
+*/
+void InventoryManagementService::loadInventoryItems()
+{
+	util::FileManager<InventoryItem> inventoryItemFileManager(config::file::INVENTORYITEM_FILE);
+	auto& inventoryItems = m_dataStore.getInventoryItems();
+	auto inventoryItemsMap = inventoryItemFileManager.load();
+	int numberOfInventoryItems = inventoryItemsMap.getSize();
+	for (int index = 0; index < numberOfInventoryItems; index++)
+	{
+		inventoryItems[inventoryItemsMap.getKeyAt(index)] = inventoryItemsMap.getValueAt(index);
+	}
+}
+
+/*
+Function: saveInventoryItems
+Description: Saves inventory items from the datastore to persistent storage.
+			 Uses FileManager to serialize inventory items into the configured file.
+Parameters:
+	- None
+Returns:
+	- void
+*/
+void InventoryManagementService::saveInventoryItems()
+{
+	util::FileManager<InventoryItem> inventoryItemFileManager(config::file::INVENTORYITEM_FILE);
+	auto& inventoryItems = m_dataStore.getInventoryItems();
+	inventoryItemFileManager.save(inventoryItems);
+}
+
+/*
+Function: loadObservers
+Description: Loads observer IDs from persistent storage and attaches corresponding
+			 users as observers to the InventoryManagementService.
+Parameters:
+	- None
+Returns:
+	- void
+*/
+void InventoryManagementService::loadObservers()
+{
+	util::loadObservers(config::file::INVENTORYMANAGEMENTOBSERVERS, this, m_dataStore);
+}
+
+/*
+Function: saveObservers
+Description: Saves the current observer IDs of the InventoryManagementService
+			 to persistent storage for future retrieval.
+Parameters:
+	- None
+Returns:
+	- void
+*/
+void InventoryManagementService::saveObservers()
+{
+	util::saveObservers(config::file::INVENTORYMANAGEMENTOBSERVERS, this);
+}
+
 /*
 Function: addInventoryItem
 Description: Creates a new inventory item using the Factory and inserts it
@@ -102,11 +190,8 @@ Return type: void
 */
 void InventoryManagementService::addInventoryItem(const std::string& partName, int quantity, double price)
 {
-	DataStoreLockGuard lock(m_dataStore);
-	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
     InventoryItem* newItem = Factory::getObject<InventoryItem>(partName, quantity, price);
-	trackedInventoryItemMap.insert(newItem->getId(), util::createNewRecord(newItem));
+    m_dataStore.getInventoryItems().insert(newItem->getId(), newItem);
-	m_dataStore.saveInventoryItems();
 }
 
 /*
@@ -118,22 +203,16 @@ Return type: void
 */
 void InventoryManagementService::addInventoryItemStock(const std::string& selectedItemId, int quantity)
 {
-	DataStoreLockGuard lock(m_dataStore);
+    int index = m_dataStore.getInventoryItems().find(selectedItemId);
-	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+    if (index != -1)
-	int index = trackedInventoryItemMap.find(selectedItemId);
+    {
-	if (index == -1)
+        InventoryItem* item = m_dataStore.getInventoryItems().getValueAt(index);
-	{
+        if (item != nullptr)
-		throw std::runtime_error("Inventory update failed: Item ID '" + selectedItemId + "' not found.");
+        {
-	}
+            int totalQuantity = item->getQuantity() + quantity;
-	InventoryItem* item = trackedInventoryItemMap.getValueAt(index).data;
+            item->setQuantity(totalQuantity);
-	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();
 }
 
 /*
@@ -144,10 +223,7 @@ Return type: util::Map<std::string, InventoryItem*>
 */
 util::Map<std::string, InventoryItem*> InventoryManagementService::getInventoryItems()
 {
-	DataStoreLockGuard lock(m_dataStore);
+	return m_dataStore.getInventoryItems();
-	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
-	auto inventoryMap = util::getObjects(trackedInventoryItemMap);
-	return inventoryMap;
 }
 
 /*
@@ -158,21 +234,15 @@ Return type: void
 */
 void InventoryManagementService::removeInventoryItem(const std::string& inventoryItemID)
 {
-	DataStoreLockGuard lock(m_dataStore);
+    int index = m_dataStore.getInventoryItems().find(inventoryItemID);
-	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+    if (index != -1)
-	int index = trackedInventoryItemMap.find(inventoryItemID);
+    {
-	if (index == -1)
+        InventoryItem* item = m_dataStore.getInventoryItems().getValueAt(index);
-	{
+        if (item != nullptr)
-		throw std::runtime_error("Inventory removal failed: Item ID '" + inventoryItemID + "' not found.");
+        {
-	}
+            item->setState(util::State::INACTIVE);
-	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();
 }
 
 /*
@@ -183,19 +253,12 @@ Return type: InventoryItem*
 */
 InventoryItem* InventoryManagementService::getInventoryItem(const std::string& inventoryItemID)
 {
-	DataStoreLockGuard lock(m_dataStore);
+    int index = m_dataStore.getInventoryItems().find(inventoryItemID);
-	auto& trackedInventoryItemMap = m_dataStore.getInventoryItems();
+    if (index != -1)
-    int index = trackedInventoryItemMap.find(inventoryItemID);
-    if (index == -1)
     {
-		return nullptr;
+        return m_dataStore.getInventoryItems().getValueAt(index);
     }
-	InventoryItem* inventoryItem = trackedInventoryItemMap.getValueAt(index).data;
+    return nullptr;
-	if (inventoryItem == nullptr)
-	{
-		throw std::runtime_error("Item ID does not exist.");
-	}
-	return inventoryItem;
 }
 
 /*

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/InventoryManagementService.h

@@ -33,6 +33,8 @@ public:
     void sendNotification(User* user, const std::string& title, const std::string& message) override;
     void attach(User* user) override;
     void detach(User* user) override;
+    void loadInventoryItems();
+    void saveInventoryItems();
     void loadObservers();
     void saveObservers();
 };

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

@@ -20,6 +20,9 @@ Date:19-May-2026
 #include "UserManagementService.h"
 #include "Vector.h"
 #include "Validator.h"
+#include "Utility.h"
+#include "TrackedRecord.h"
+#include "DataStoreLockGuard.h"
 
 /*
 Function: ensureAdminExists
@@ -31,12 +34,13 @@ Return type: void
 */
 void UserManagementService::ensureAdminExists()
 {
+	DataStoreLockGuard lock(m_dataStore);
 	auto& usersMap = m_dataStore.getUsers();
 	int usersMapSize = usersMap.getSize();
 	bool isAdminFound = false;
 	for (int index = 0; index < usersMapSize; index++)
 	{
-		User* user = usersMap.getValueAt(index);
+		User* user = usersMap.getValueAt(index).data;
 		if (user && user->getUserType() == util::UserType::ADMIN)
 		{
 			isAdminFound = true;
@@ -73,7 +77,9 @@ void UserManagementService::createUser(const std::string& username, const std::s
 	InventoryManagementService inventoryManagementService;
 	PaymentManagementService paymentManagementService;
 	ServiceManagementService serviceManagementService;
-	auto& usersMap = m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	auto usersMap = util::getObjects(trackedUsersMap);
 	if (util::isUsernameDuplicate(username, usersMap))
 	{
 		throw std::runtime_error("Username already exists");
@@ -87,13 +93,14 @@ void UserManagementService::createUser(const std::string& username, const std::s
 		throw std::runtime_error("Phone already exists");
 	}
 	User* newUser = Factory::getObject<User>(username, password, name, phone, email, type);
-	usersMap.insert(newUser->getId(), newUser);
+	trackedUsersMap.insert(newUser->getId(), util::createNewRecord(newUser));
 	paymentManagementService.attach(newUser);
 	serviceManagementService.attach(newUser);
 	if (newUser->getUserType() == util::UserType::ADMIN)
 	{
 		inventoryManagementService.attach(newUser);
 	}
+	m_dataStore.saveUsers();
 }
 
 /*
@@ -107,19 +114,24 @@ Return type: void
 */
 void UserManagementService::updateUserDetails(const std::string& userID, const std::string& email, const std::string& phone)
 {
-	auto& usersMap = m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
-	int index = usersMap.find(userID);
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	auto usersMap = util::getObjects(trackedUsersMap);
+	int index = trackedUsersMap.find(userID);
 	if (index == -1)
 	{
 		throw std::runtime_error("User does not exist!\n");
 	}
-	User* user = usersMap.getValueAt(index);
+	User* user = trackedUsersMap.getValueAt(index).data;
+	bool isModified = false;
 	if (email != user->getEmail())
 	{
 		if (util::isEmailDuplicate(email, usersMap))
 		{
 			throw std::runtime_error("Email already exists!\n");
 		}
+		user->setEmail(email);
+		isModified = true;
 	}
 	if (phone != user->getPhone())
 	{
@@ -127,9 +139,14 @@ void UserManagementService::updateUserDetails(const std::string& userID, const s
 		{
 			throw std::runtime_error("Phone number already exists!\n");
 		}
+		user->setPhone(phone);
+		isModified = true;
+	}
+	if (isModified)
+	{
+		trackedUsersMap.getValueAt(index).state = RecordState::MODIFIED;
+		m_dataStore.saveUsers();
 	}
-	user->setEmail(email);
-	user->setPhone(phone);
 }
 
 /*
@@ -144,12 +161,13 @@ Throws:
 */
 util::Vector<Notification*> UserManagementService::getUserNotifications(const std::string& userID)
 {
-	auto& usersMap = m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
-	if (usersMap.find(userID) == -1)
+	auto& trackedUsersMap = m_dataStore.getUsers(); 
+	if (trackedUsersMap.find(userID) == -1)
 	{
 		throw std::runtime_error("No user found with given UserID");
 	}
-	User* user = usersMap[userID];
+	User* user = trackedUsersMap[userID].data;
 	if (user)
 	{
 		auto& notifications = user->getNotifications();
@@ -169,97 +187,41 @@ util::Vector<Notification*> UserManagementService::getUserNotifications(const st
 
 /*
 Function: deleteNotification
-Description: Deletes a specific notification associated with a given user ID.
+Description: Marks a specific notification associated with a given user
+			 as inactive.
 Parameters:
 	- notificationID: The unique ID of the notification to be deleted.
 	- userID: The unique ID of the user whose notification is to be deleted.
 Returns:
 	- void
 Throws:
-	- std::runtime_error if no user is found with the given UserID or if no notification is found with the given NotificationID.
+	- std::runtime_error if no user is found with the given UserID or
+	  if no notification is found with the given NotificationID.
 */
 void UserManagementService::deleteNotification(const std::string& notificationID, const std::string& userID)
 {
-	auto& usersMap = m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
-	if (usersMap.find(userID) == -1)
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	auto& trackedNotificationsMap = m_dataStore.getNotifications();
+	int userIndex = trackedUsersMap.find(userID);
+	if (userIndex == -1)
 	{
 		throw std::runtime_error("No user found with given UserID");
 	}
-	User* user = usersMap[userID];
+	User* user = trackedUsersMap.getValueAt(userIndex).data;
 	auto& notifications = user->getNotifications();
 	if (notifications.find(notificationID) == -1)
 	{
 		throw std::runtime_error("No notification found with given NotificationID");
 	}
-	notifications.remove(notificationID);
+	int notificationIndex = trackedNotificationsMap.find(notificationID);
-}
+	if (notificationIndex == -1)
-
+	{
-/*
+		throw std::runtime_error("No notification found with given NotificationID");
-Function: loadUsers
+	}
-Description: Loads users and notifications from persistent storage into the datastore.
+	notifications[notificationID]->setState(util::State::INACTIVE);
-             Validates that each notification’s recipient exists and attaches the
+	trackedNotificationsMap.getValueAt(notificationIndex).state = RecordState::MODIFIED;
-             notification to the corresponding user.
+	m_dataStore.saveNotifications();
-Parameters:
-    - None
-Returns:
-    - void
-Throws:
-    - std::runtime_error if a notification recipient user ID is invalid
-*/
-void UserManagementService::loadUsers()
-{
-    util::FileManager<User> userFileManager(config::file::USER_FILE);
-    util::FileManager<Notification> notificationFileManager(config::file::NOTIFICATION_FILE);
-    auto& users = m_dataStore.getUsers();
-    auto usersMap = userFileManager.load();
-    auto notificationsMap = notificationFileManager.load();
-    int numberOfUsers = usersMap.getSize();
-    int numberOfNotifications = notificationsMap.getSize();
-    for (int index = 0; index < numberOfUsers; index++)
-    {
-        users[usersMap.getKeyAt(index)] = usersMap.getValueAt(index);
-    }
-    for (int index = 0; index < numberOfNotifications; index++)
-    {
-        Notification* notification = notificationsMap.getValueAt(index);
-        const std::string& recipientUserId = notification->getRecipientUserId();
-        int userIndex = users.find(recipientUserId);
-        if (userIndex == -1)
-        {
-            throw std::runtime_error("Invalid recipient user ID");
-        }
-        User* user = users.getValueAt(userIndex);
-        user->addNotification(notification);
-    }
-}
-
-/*
-Function: saveUsers
-Description: Saves users and their notifications from the datastore to persistent storage.
-             Collects notifications from all users into a single map before saving.
-Parameters:
-    - None
-Returns:
-    - void
-*/
-void UserManagementService::saveUsers()
-{
-    util::FileManager<User> userFileManager(config::file::USER_FILE);
-    util::FileManager<Notification> notificationFileManager(config::file::NOTIFICATION_FILE);
-    auto& users = m_dataStore.getUsers();
-    util::Map<std::string, Notification*> notifications;
-    for (int userIndex = 0; userIndex < users.getSize(); userIndex++)
-    {
-        User* user = users.getValueAt(userIndex);
-        auto& userNotifications = user->getNotifications();
-        for (int notificationIndex = 0; notificationIndex < userNotifications.getSize(); notificationIndex++)
-        {
-            notifications[userNotifications.getKeyAt(notificationIndex)] =
-                userNotifications.getValueAt(notificationIndex);
-        }
-    }
-    userFileManager.save(users);
-    notificationFileManager.save(notifications);
 }
 
 /*
@@ -270,7 +232,9 @@ Return type: util::Map<std::string, User*>
 */
 util::Map<std::string, User*> UserManagementService::getUsers()
 {
-	return m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
+	auto users = util::getObjects(m_dataStore.getUsers());
+	return users;
 }
 
 /*
@@ -281,10 +245,12 @@ Return type: User*
 */
 User* UserManagementService::getUser(const std::string& userID)
 {
-	int index = m_dataStore.getUsers().find(userID);
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	int index = trackedUsersMap.find(userID);
 	if (index != -1)
 	{
-		return m_dataStore.getUsers().getValueAt(index);
+		return trackedUsersMap.getValueAt(index).data;
 	}
 	return nullptr;
 }
@@ -300,10 +266,12 @@ void UserManagementService::removeUser(const std::string& userID)
 	InventoryManagementService inventoryManagementService;
 	PaymentManagementService paymentManagementService;
 	ServiceManagementService serviceManagementService;
-	int index = m_dataStore.getUsers().find(userID);
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	int index = trackedUsersMap.find(userID);
 	if (index != -1)
 	{
-		User* user = m_dataStore.getUsers().getValueAt(index);
+		User* user = trackedUsersMap.getValueAt(index).data;
 		if (user != nullptr)
 		{
 			if (user->getUserType() == util::UserType::CUSTOMER)
@@ -314,21 +282,37 @@ void UserManagementService::removeUser(const std::string& userID)
 			{
 				serviceManagementService.cancelTechnicianJobs(userID);
 			}
-			user->setState(util::State::INACTIVE);
 			inventoryManagementService.detach(user);
 			paymentManagementService.detach(user);
 			serviceManagementService.detach(user);
+			user->setState(util::State::INACTIVE);
+			trackedUsersMap.getValueAt(index).state = RecordState::MODIFIED;
+			m_dataStore.saveUsers();
 		}
 	}
 }
 
+/*
+Function: getUsers
+Description: Retrieves all active users of the specified type from
+			 the DataStore.
+Parameters:
+	- type: The user type to filter by
+			(ADMIN, CUSTOMER, or TECHNICIAN).
+Returns:
+	- util::Map<std::string, User*>:
+	  Collection of active users matching the specified type,
+	  keyed by user ID.
+*/
 util::Map<std::string, User*> UserManagementService::getUsers(util::UserType type) 
 {
-	util::Map<std::string, User*>& currentUsers = m_dataStore.getUsers();
+	DataStoreLockGuard lock(m_dataStore);
+	auto& trackedUsersMap = m_dataStore.getUsers();
+	util::Map<std::string, User*> currentUsers = util::getObjects(trackedUsersMap);
 	util::Map<std::string, User*> filteredUsersMap;
-	for (int iterator = 0; iterator < currentUsers.getSize(); iterator++)
+	for (int index = 0; index < currentUsers.getSize(); index++)
 	{
-		User* currentUser = currentUsers.getValueAt(iterator);
+		User* currentUser = currentUsers.getValueAt(index);
 		if (currentUser && currentUser->getState() == util::State::ACTIVE && currentUser->getUserType() == type)
 		{
 			filteredUsersMap.insert(currentUser->getId(), currentUser);

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/UserManagementService.h

@@ -31,6 +31,4 @@ public:
     util::Vector<Notification*> getUserNotifications(const std::string& userID);
     void deleteNotification(const std::string& notificationID, const std::string& userID);
     void ensureAdminExists();
-    void loadUsers();
-    void saveUsers();
 };

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/UserInterface.cpp

@@ -27,8 +27,11 @@ void UserInterface::run()
 {
 	try
 	{
-		m_controller.loadSystemData();
+		if (!m_controller.initialize())
-		m_controller.runSystemChecks();
+		{
+			std::cout << "Error: Failed to initialize the system!";
+			return;
+		}
 		bool isMenuActive = true;
 		while (isMenuActive)
 		{
@@ -49,7 +52,7 @@ void UserInterface::run()
 				util::pressEnter();
 			}
 		}
-		m_controller.saveSystemData();
+		m_controller.shutdown();
 	}
 	catch (const std::invalid_argument& exception)
 	{