Phase 4 - synch engine complete

lib/data/sync/models/sync_operation.dart

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+import 'sync_status.dart';
+
+/// Represents a sync operation in the queue.
+class SyncOperation {
+  /// Unique identifier for the operation.
+  final String id;
+
+  /// Type of sync operation.
+  final SyncOperationType type;
+
+  /// Item ID being synced.
+  final String itemId;
+
+  /// Source of the sync (local, immich, nostr).
+  final String source;
+
+  /// Target of the sync (local, immich, nostr).
+  final String target;
+
+  /// Current status of the operation.
+  SyncStatus status;
+
+  /// Priority of the operation.
+  final SyncPriority priority;
+
+  /// Number of retry attempts.
+  int retryCount;
+
+  /// Maximum number of retries allowed.
+  final int maxRetries;
+
+  /// Error message if operation failed.
+  String? error;
+
+  /// Timestamp when operation was created.
+  final int createdAt;
+
+  /// Timestamp when operation was last updated.
+  int updatedAt;
+
+  /// Creates a [SyncOperation] instance.
+  SyncOperation({
+    required this.id,
+    required this.type,
+    required this.itemId,
+    required this.source,
+    required this.target,
+    this.status = SyncStatus.pending,
+    this.priority = SyncPriority.normal,
+    this.retryCount = 0,
+    this.maxRetries = 3,
+    this.error,
+    int? createdAt,
+    int? updatedAt,
+  })  : createdAt = createdAt ?? DateTime.now().millisecondsSinceEpoch,
+        updatedAt = updatedAt ?? DateTime.now().millisecondsSinceEpoch;
+
+  /// Creates a [SyncOperation] from JSON.
+  factory SyncOperation.fromJson(Map<String, dynamic> json) {
+    return SyncOperation(
+      id: json['id'] as String,
+      type: SyncOperationType.values.firstWhere(
+        (e) => e.toString() == json['type'],
+        orElse: () => SyncOperationType.upload,
+      ),
+      itemId: json['itemId'] as String,
+      source: json['source'] as String,
+      target: json['target'] as String,
+      status: SyncStatus.values.firstWhere(
+        (e) => e.toString() == json['status'],
+        orElse: () => SyncStatus.pending,
+      ),
+      priority: SyncPriority.values.firstWhere(
+        (e) => e.toString() == json['priority'],
+        orElse: () => SyncPriority.normal,
+      ),
+      retryCount: json['retryCount'] as int? ?? 0,
+      maxRetries: json['maxRetries'] as int? ?? 3,
+      error: json['error'] as String?,
+      createdAt: json['createdAt'] as int,
+      updatedAt: json['updatedAt'] as int,
+    );
+  }
+
+  /// Converts [SyncOperation] to JSON.
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'type': type.toString(),
+      'itemId': itemId,
+      'source': source,
+      'target': target,
+      'status': status.toString(),
+      'priority': priority.toString(),
+      'retryCount': retryCount,
+      'maxRetries': maxRetries,
+      'error': error,
+      'createdAt': createdAt,
+      'updatedAt': updatedAt,
+    };
+  }
+
+  /// Marks the operation as failed with an error.
+  void markFailed(String errorMessage) {
+    status = SyncStatus.failed;
+    error = errorMessage;
+    updatedAt = DateTime.now().millisecondsSinceEpoch;
+  }
+
+  /// Marks the operation as successful.
+  void markSuccess() {
+    status = SyncStatus.success;
+    error = null;
+    updatedAt = DateTime.now().millisecondsSinceEpoch;
+  }
+
+  /// Increments retry count and updates status.
+  void incrementRetry() {
+    retryCount++;
+    status = SyncStatus.pending;
+    updatedAt = DateTime.now().millisecondsSinceEpoch;
+  }
+
+  /// Checks if the operation can be retried.
+  bool canRetry() {
+    return retryCount < maxRetries && status == SyncStatus.failed;
+  }
+
+  @override
+  String toString() {
+    return 'SyncOperation(id: $id, type: $type, itemId: $itemId, status: $status, retries: $retryCount/$maxRetries)';
+  }
+}
+
+/// Type of sync operation.
+enum SyncOperationType {
+  /// Upload operation (local to remote).
+  upload,
+
+  /// Download operation (remote to local).
+  download,
+
+  /// Bidirectional sync (merge).
+  sync,
+}
+

lib/data/sync/models/sync_status.dart

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+/// Status of a sync operation.
+enum SyncStatus {
+  /// Sync operation is pending (queued).
+  pending,
+
+  /// Sync operation is in progress.
+  syncing,
+
+  /// Sync operation completed successfully.
+  success,
+
+  /// Sync operation failed.
+  failed,
+}
+
+/// Priority level for sync operations.
+enum SyncPriority {
+  /// Low priority (background sync).
+  low,
+
+  /// Normal priority.
+  normal,
+
+  /// High priority (user-initiated).
+  high,
+}
+
+/// Resolution strategy for conflicts.
+enum ConflictResolution {
+  /// Use local version (prefer local data).
+  useLocal,
+
+  /// Use remote version (prefer remote data).
+  useRemote,
+
+  /// Merge both versions.
+  merge,
+
+  /// Keep the most recent version based on timestamp.
+  useLatest,
+}
+