Add welcome popup, changelog system, and account deletion button

lib/services/changelog_service.dart

@@ -0,0 +1,154 @@
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'version_service.dart';
+
+/// Service for managing changelog data and first launch detection
+class ChangelogService {
+  static final ChangelogService _instance = ChangelogService._internal();
+  factory ChangelogService() => _instance;
+  ChangelogService._internal();
+
+  static const String _lastSeenVersionKey = 'last_seen_version';
+  static const String _hasSeenWelcomeKey = 'has_seen_welcome';
+
+  Map<String, dynamic>? _changelogData;
+  bool _initialized = false;
+
+  /// Initialize the service by loading changelog data
+  Future<void> init() async {
+    if (_initialized) return;
+    
+    try {
+      final String jsonString = await rootBundle.loadString('assets/changelog.json');
+      _changelogData = json.decode(jsonString);
+      _initialized = true;
+      debugPrint('[ChangelogService] Loaded changelog with ${_changelogData?.keys.length ?? 0} versions');
+    } catch (e) {
+      debugPrint('[ChangelogService] Failed to load changelog: $e');
+      _changelogData = {};
+      _initialized = true; // Mark as initialized even on failure to prevent repeated attempts
+    }
+  }
+
+  /// Check if this is the first app launch ever
+  Future<bool> isFirstLaunch() async {
+    final prefs = await SharedPreferences.getInstance();
+    return !prefs.containsKey(_lastSeenVersionKey);
+  }
+
+  /// Check if user has seen the welcome popup (separate from version tracking)
+  Future<bool> hasSeenWelcome() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(_hasSeenWelcomeKey) ?? false;
+  }
+
+  /// Mark that user has seen the welcome popup
+  Future<void> markWelcomeSeen() async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_hasSeenWelcomeKey, true);
+  }
+
+  /// Check if app version has changed since last launch
+  Future<bool> hasVersionChanged() async {
+    final prefs = await SharedPreferences.getInstance();
+    final lastSeenVersion = prefs.getString(_lastSeenVersionKey);
+    final currentVersion = VersionService().version;
+    
+    return lastSeenVersion != currentVersion;
+  }
+
+  /// Update the stored version to current version
+  Future<void> updateLastSeenVersion() async {
+    final prefs = await SharedPreferences.getInstance();
+    final currentVersion = VersionService().version;
+    await prefs.setString(_lastSeenVersionKey, currentVersion);
+    debugPrint('[ChangelogService] Updated last seen version to: $currentVersion');
+  }
+
+  /// Get changelog content for the current version
+  String? getChangelogForCurrentVersion() {
+    if (!_initialized || _changelogData == null) {
+      debugPrint('[ChangelogService] Not initialized or no changelog data');
+      return null;
+    }
+
+    final currentVersion = VersionService().version;
+    final versionData = _changelogData![currentVersion] as Map<String, dynamic>?;
+    
+    if (versionData == null) {
+      debugPrint('[ChangelogService] No changelog entry found for version: $currentVersion');
+      return null;
+    }
+
+    final content = versionData['content'] as String?;
+    return (content?.isEmpty == true) ? null : content;
+  }
+
+  /// Get changelog content for a specific version
+  String? getChangelogForVersion(String version) {
+    if (!_initialized || _changelogData == null) return null;
+    
+    final versionData = _changelogData![version] as Map<String, dynamic>?;
+    if (versionData == null) return null;
+    
+    final content = versionData['content'] as String?;
+    return (content?.isEmpty == true) ? null : content;
+  }
+
+  /// Get all changelog entries (for settings page)
+  Map<String, String> getAllChangelogs() {
+    if (!_initialized || _changelogData == null) return {};
+
+    final Map<String, String> result = {};
+    
+    for (final entry in _changelogData!.entries) {
+      final version = entry.key;
+      final versionData = entry.value as Map<String, dynamic>?;
+      final content = versionData?['content'] as String?;
+      
+      // Only include versions with non-empty content
+      if (content != null && content.isNotEmpty) {
+        result[version] = content;
+      }
+    }
+    
+    return result;
+  }
+
+  /// Determine what popup (if any) should be shown
+  Future<PopupType> getPopupType() async {
+    // Ensure services are initialized
+    if (!_initialized) await init();
+
+    final isFirstLaunch = await this.isFirstLaunch();
+    final hasSeenWelcome = await this.hasSeenWelcome();
+    final hasVersionChanged = await this.hasVersionChanged();
+
+    // First launch and haven't seen welcome
+    if (isFirstLaunch || !hasSeenWelcome) {
+      return PopupType.welcome;
+    }
+
+    // Version changed and there's changelog content
+    if (hasVersionChanged) {
+      final changelogContent = getChangelogForCurrentVersion();
+      if (changelogContent != null) {
+        return PopupType.changelog;
+      }
+    }
+
+    return PopupType.none;
+  }
+
+  /// Check if the service is properly initialized
+  bool get isInitialized => _initialized;
+}
+
+/// Types of popups that can be shown
+enum PopupType {
+  none,
+  welcome,
+  changelog,
+}