import '../../core/exceptions.dart';
import '../api/tasks_api.dart';
import '../local/database.dart';
import '../models/task.dart';

/// Tasks repository with read-through caching (Phase 1+2) and offline-write
/// queueing (Phase 3). See `notes_repository.dart` for the full pattern.
class TasksRepository {
  final TasksApi _api;
  final FabledDatabase _db;

  const TasksRepository(this._api, this._db);

  Future<List<Task>> getAll() async {
    try {
      final tasks = await _api.getAll();
      await _db.replaceAllTasks(tasks);
      return tasks;
    } on NetworkException {
      final cached = await _db.getAllTasks();
      if (cached.isEmpty) rethrow;
      return cached;
    }
  }

  Future<Task> getOne(int id) async {
    try {
      final task = await _api.getOne(id);
      await _db.upsertTask(task);
      return task;
    } on NetworkException {
      final cached = await _db.getTask(id);
      if (cached == null) rethrow;
      return cached;
    }
  }

  Future<List<Task>> getByProject(int projectId) async {
    try {
      final tasks = await _api.getByProject(projectId);
      for (final t in tasks) {
        await _db.upsertTask(t);
      }
      return tasks;
    } on NetworkException {
      return _db.getTasksByProject(projectId);
    }
  }

  Future<List<Task>> getSubTasks(int parentId) async {
    try {
      final tasks = await _api.getSubTasks(parentId);
      for (final t in tasks) {
        await _db.upsertTask(t);
      }
      return tasks;
    } on NetworkException {
      return _db.getSubTasks(parentId);
    }
  }

  Future<Task> create({
    required String title,
    String? description,
    required TaskStatus status,
    required TaskPriority priority,
    DateTime? dueDate,
    int? projectId,
    int? parentId,
  }) async {
    try {
      final task = await _api.create(
        title: title,
        description: description,
        status: status,
        priority: priority,
        dueDate: dueDate,
        projectId: projectId,
        parentId: parentId,
      );
      await _db.upsertTask(task);
      return task;
    } on NetworkException {
      final tempId = await _db.nextTempId();
      final now = DateTime.now();
      final optimistic = Task(
        id: tempId,
        title: title,
        description: description,
        status: status,
        priority: priority,
        dueDate: dueDate,
        projectId: projectId,
        parentId: parentId,
        createdAt: now,
        updatedAt: now,
      );
      await _db.upsertTask(optimistic);
      await _db.enqueuePending(
        domain: kSyncDomainTasks,
        verb: kWriteVerbCreate,
        tempId: tempId,
        payload: {
          'title': title,
          'description': description,
          'status': status.value,
          'priority': priority.value,
          'due_date': dueDate?.toIso8601String(),
          'project_id': projectId,
          'parent_id': parentId,
        },
      );
      return optimistic;
    }
  }

  Future<Task> update(int id, Map<String, dynamic> fields) async {
    try {
      final updated = await _api.update(id, fields);
      await _db.upsertTask(updated);
      return updated;
    } on NetworkException {
      final cached = await _db.getTask(id);
      if (cached == null) rethrow;
      final optimistic = _applyTaskFields(cached, fields);
      await _db.upsertTask(optimistic);
      if (id < 0) {
        final queued = await _db.findQueuedCreate(kSyncDomainTasks, id);
        if (queued != null) {
          await _db.updatePendingPayload(queued.id, fields);
          return optimistic;
        }
      }
      await _db.enqueuePending(
        domain: kSyncDomainTasks,
        verb: kWriteVerbUpdate,
        targetId: id,
        payload: fields,
        baselineUpdatedAt: cached.updatedAt,
      );
      return optimistic;
    }
  }

  Future<void> delete(int id) async {
    try {
      await _api.delete(id);
      await _db.deleteTask(id);
    } on NetworkException {
      if (id < 0) {
        final queued = await _db.findQueuedCreate(kSyncDomainTasks, id);
        if (queued != null) await _db.deletePending(queued.id);
        await _db.deleteTask(id);
        return;
      }
      await _db.deleteTask(id);
      await _db.enqueuePending(
        domain: kSyncDomainTasks,
        verb: kWriteVerbDelete,
        targetId: id,
      );
    }
  }
}

/// Applies a partial-fields map (the same shape sent to the PUT endpoint)
/// to a cached Task so the UI can show the edit immediately.
Task _applyTaskFields(Task t, Map<String, dynamic> f) {
  return Task(
    id: t.id,
    title: f['title'] as String? ?? t.title,
    description:
        f.containsKey('body') ? f['body'] as String? : t.description,
    status: f.containsKey('status')
        ? TaskStatusExtension.fromString(f['status'] as String?)
        : t.status,
    priority: f.containsKey('priority')
        ? TaskPriorityExtension.fromString(f['priority'] as String?)
        : t.priority,
    dueDate: f.containsKey('due_date')
        ? (f['due_date'] is String
            ? DateTime.tryParse(f['due_date'] as String)
            : null)
        : t.dueDate,
    projectId: f.containsKey('project_id')
        ? f['project_id'] as int?
        : t.projectId,
    milestoneId: f.containsKey('milestone_id')
        ? f['milestone_id'] as int?
        : t.milestoneId,
    parentId:
        f.containsKey('parent_id') ? f['parent_id'] as int? : t.parentId,
    createdAt: t.createdAt,
    updatedAt: t.updatedAt,
  );
}