import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import '../../features/rides/ride_state_machine.dart';
import 'sync_manager.dart';
import 'sync_providers.dart';

/// External observer listening for ride state machine transitions.
/// Automatically enqueues completed rides into the synchronization pipeline
/// without modifying or blocking the frozen RideStateMachine.
class SyncObserver {
  final SyncManager _syncManager;
  int? _lastEnqueuedRideId;

  SyncObserver(this._syncManager);

  /// Called when the RideStateMachine state changes in Riverpod
  void onRideSessionChanged(RideSession? previous, RideSession next) {
    // Detect transition into finished state
    final wasFinished = previous?.state == RideState.finished;
    final isFinished = next.state == RideState.finished;
    final completedRideId = next.dbId;

    if (!wasFinished && isFinished && completedRideId != null) {
      if (_lastEnqueuedRideId != completedRideId) {
        _lastEnqueuedRideId = completedRideId;
        debugPrint('[SyncObserver] Ride #$completedRideId completed, enqueuing to SyncManager');
        _syncManager.enqueueRide(completedRideId);
      }
    }
  }
}

/// Riverpod provider establishing the active SyncObserver listener
final syncObserverProvider = Provider<SyncObserver>((ref) {
  final manager = ref.watch(syncManagerProvider);
  final observer = SyncObserver(manager);

  // External, non-invasive observation of the frozen RideStateMachine
  ref.listen<RideSession>(
    rideStateMachineProvider,
    (previous, next) => observer.onRideSessionChanged(previous, next),
  );

  return observer;
});