feat: Implement update checker and dialog for available app updates with localization support

lib/services/build_info_service.dart

@@ -0,0 +1,54 @@
+import 'dart:io' show Platform;
+import 'package:flutter/services.dart';
+import 'package:flutter/foundation.dart';
+
+/// Service for accessing build information from native platform code
+/// Currently supports Android only - returns "unknown" for other platforms
+class BuildInfoService {
+  static final BuildInfoService _instance = BuildInfoService._internal();
+  factory BuildInfoService() => _instance;
+  BuildInfoService._internal();
+
+  static const MethodChannel _channel = MethodChannel('com.meshcore.sar/build_info');
+
+  String? _cachedCommitHash;
+
+  /// Get the commit hash that was embedded during build time
+  /// Returns "unknown" if:
+  /// - Not running on Android
+  /// - Platform channel call fails
+  /// - Build was not configured with COMMIT_HASH
+  Future<String> getCommitHash() async {
+    // Return cached value if available
+    if (_cachedCommitHash != null) {
+      return _cachedCommitHash!;
+    }
+
+    // Only Android has the platform channel implementation
+    if (!Platform.isAndroid) {
+      debugPrint('[BuildInfoService] Not on Android platform, returning "unknown"');
+      _cachedCommitHash = 'unknown';
+      return _cachedCommitHash!;
+    }
+
+    try {
+      final String commitHash = await _channel.invokeMethod('getCommitHash');
+      _cachedCommitHash = commitHash;
+      debugPrint('[BuildInfoService] Commit hash: $commitHash');
+      return commitHash;
+    } on PlatformException catch (e) {
+      debugPrint('[BuildInfoService] Failed to get commit hash: ${e.message}');
+      _cachedCommitHash = 'unknown';
+      return _cachedCommitHash!;
+    } catch (e) {
+      debugPrint('[BuildInfoService] Unexpected error getting commit hash: $e');
+      _cachedCommitHash = 'unknown';
+      return _cachedCommitHash!;
+    }
+  }
+
+  /// Clear cached commit hash (useful for testing)
+  void clearCache() {
+    _cachedCommitHash = null;
+  }
+}

lib/services/update_checker_service.dart

@@ -0,0 +1,135 @@
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:http/http.dart' as http;
+import '../models/update_info.dart';
+import 'build_info_service.dart';
+
+/// Service for checking if a new app version is available
+/// Compares current build's commit hash with latest manifest from server
+class UpdateCheckerService {
+  static final UpdateCheckerService _instance = UpdateCheckerService._internal();
+  factory UpdateCheckerService() => _instance;
+  UpdateCheckerService._internal();
+
+  final BuildInfoService _buildInfoService = BuildInfoService();
+
+  // Manifest URL for the latest unstable build
+  static const String _manifestUrl = 'https://meshcore-sar.dz0ny.dev/unstable/latest/manifest.json';
+
+  /// Check if an update is available
+  /// Returns UpdateInfo with availability status and download URL if available
+  Future<UpdateInfo> checkForUpdate() async {
+    try {
+      // Get current build's commit hash
+      final currentCommitHash = await _buildInfoService.getCommitHash();
+
+      // Skip check for dev builds (local development)
+      if (currentCommitHash == 'dev' || currentCommitHash == 'unknown') {
+        debugPrint('[UpdateChecker] Skipping update check for dev/unknown build');
+        return UpdateInfo.noUpdate(currentCommitHash);
+      }
+
+      debugPrint('[UpdateChecker] Current commit hash: $currentCommitHash');
+      debugPrint('[UpdateChecker] Fetching latest manifest from: $_manifestUrl');
+
+      // Fetch manifest from server
+      final response = await http.get(
+        Uri.parse(_manifestUrl),
+        headers: {'Accept': 'application/json'},
+      ).timeout(
+        const Duration(seconds: 10),
+        onTimeout: () {
+          debugPrint('[UpdateChecker] Manifest fetch timed out');
+          throw Exception('Manifest fetch timed out');
+        },
+      );
+
+      if (response.statusCode != 200) {
+        debugPrint('[UpdateChecker] Failed to fetch manifest: ${response.statusCode}');
+        return UpdateInfo.noUpdate(currentCommitHash);
+      }
+
+      // Parse manifest JSON
+      final Map<String, dynamic> manifest = json.decode(response.body);
+      final latestCommitHash = manifest['commit'] as String?;
+      final commitShort = manifest['commit_short'] as String?;
+      final buildId = manifest['build_id'] as String?;
+      final timestamp = manifest['timestamp'] as String?;
+      final artifacts = manifest['artifacts'] as List<dynamic>?;
+
+      if (latestCommitHash == null || commitShort == null) {
+        debugPrint('[UpdateChecker] Invalid manifest: missing commit information');
+        return UpdateInfo.noUpdate(currentCommitHash);
+      }
+
+      debugPrint('[UpdateChecker] Latest commit hash: $latestCommitHash');
+      debugPrint('[UpdateChecker] Latest commit short: $commitShort');
+
+      // Compare commit hashes
+      // Current hash might be full SHA or short (7 chars)
+      // Latest from manifest is full SHA
+      final isUpdateAvailable = !_compareCommitHashes(currentCommitHash, latestCommitHash);
+
+      if (!isUpdateAvailable) {
+        debugPrint('[UpdateChecker] No update available (same commit)');
+        return UpdateInfo.noUpdate(currentCommitHash);
+      }
+
+      // Find Android APK in artifacts
+      final String? apkUrl = _findAndroidApkUrl(artifacts);
+
+      if (apkUrl == null) {
+        debugPrint('[UpdateChecker] Update available but no APK found in artifacts');
+        return UpdateInfo.noUpdate(currentCommitHash);
+      }
+
+      debugPrint('[UpdateChecker] Update available! APK URL: $apkUrl');
+
+      return UpdateInfo.available(
+        currentCommitHash: currentCommitHash,
+        latestCommitHash: commitShort,
+        downloadUrl: apkUrl,
+        buildId: buildId,
+        timestamp: timestamp,
+      );
+    } catch (e) {
+      debugPrint('[UpdateChecker] Error checking for update: $e');
+      // Return no update on error to avoid disrupting app startup
+      final currentCommitHash = await _buildInfoService.getCommitHash();
+      return UpdateInfo.noUpdate(currentCommitHash);
+    }
+  }
+
+  /// Compare two commit hashes (handles both full SHA and short format)
+  bool _compareCommitHashes(String current, String latest) {
+    // Normalize to lowercase for comparison
+    final currentLower = current.toLowerCase();
+    final latestLower = latest.toLowerCase();
+
+    // Direct match
+    if (currentLower == latestLower) return true;
+
+    // Check if current is short form of latest
+    if (latestLower.startsWith(currentLower)) return true;
+
+    // Check if latest is short form of current
+    if (currentLower.startsWith(latestLower)) return true;
+
+    return false;
+  }
+
+  /// Find Android APK URL in artifacts list
+  String? _findAndroidApkUrl(List<dynamic>? artifacts) {
+    if (artifacts == null || artifacts.isEmpty) return null;
+
+    // Look for .apk file in artifacts
+    for (final artifact in artifacts) {
+      if (artifact is String && artifact.toLowerCase().endsWith('.apk')) {
+        // Construct full URL
+        return 'https://meshcore-sar.dz0ny.dev/unstable/latest/$artifact';
+      }
+    }
+
+    return null;
+  }
+}