import 'cloud_reconciliation_service.dart';
import '../../database/database.dart';
import '../auth/auth_service.dart';

abstract interface class TelemetryBundleRestore {
  Future<void> restoreTelemetryBundle({
    required String cloudRideId,
    required String objectKey,
    required int localRideId,
  });
}

class CloudRestoreResult {
  final CloudReconciliationResult metadata;
  final int telemetryRestored;
  final int telemetryPending;

  const CloudRestoreResult({
    required this.metadata,
    this.telemetryRestored = 0,
    this.telemetryPending = 0,
  });
}

/// Additive, resumable restore coordinator.
///
/// Metadata is restored first. Telemetry is deliberately delegated to a
/// worker-backed implementation because the authenticated R2 download route
/// is not available in the current backend yet. Existing local rides are never
/// deleted or overwritten by this service.
class CloudRestoreService {
  final AppDatabase _db;
  final AuthService _authService;
  final CloudReconciliationService _metadata;
  final TelemetryBundleRestore? _telemetryRestore;

  CloudRestoreService({
    required AppDatabase db,
    required AuthService authService,
    CloudReconciliationService? metadata,
    TelemetryBundleRestore? telemetryRestore,
  })  : _db = db,
        _authService = authService,
        _metadata = metadata ?? CloudReconciliationService(db: db, authService: authService),
        _telemetryRestore = telemetryRestore;

  Future<CloudRestoreResult> restore() async {
    final user = _authService.currentUser;
    if (user == null || user.isAnonymous) {
      throw StateError('Authentication is required to restore MotorCloud data.');
    }

    final metadataResult = await _metadata.reconcileMetadata();
    if (_telemetryRestore == null) {
      return CloudRestoreResult(
        metadata: metadataResult,
        telemetryPending: metadataResult.added,
      );
    }

    final snapshot = await _metadataCloudRides(user.uid);
    var restored = 0;
    var pending = 0;

    for (final document in snapshot) {
      final data = document.data();
      final objectKey = _readObjectKey(data);
      if (objectKey == null) {
        pending++;
        continue;
      }

      final localRows = await _db.customSelect(
        'SELECT id FROM rides WHERE cloud_ride_id = ?',
        variables: [Variable<String>(document.id)],
      ).get();
      if (localRows.isEmpty) {
        pending++;
        continue;
      }

      final localRideId = localRows.first.data['id'];
      if (localRideId is! int) {
        pending++;
        continue;
      }

      try {
        await _telemetryRestore!.restoreTelemetryBundle(
          cloudRideId: document.id,
          objectKey: objectKey,
          localRideId: localRideId,
        );
        restored++;
      } catch (_) {
        // A failed telemetry download is resumable and must not invalidate the
        // metadata restore or delete the local ride.
        pending++;
      }
    }

    return CloudRestoreResult(
      metadata: metadataResult,
      telemetryRestored: restored,
      telemetryPending: pending,
    );
  }

  Future<List<CloudRideSnapshot>> _metadataCloudRides(String uid) async {
    // This method intentionally uses the same Firestore source through the
    // metadata service's public reconciliation boundary. The telemetry phase
    // will be replaced with a paginated cloud index once restore scales beyond
    // the initial account-sized collection.
    final rows = await _db.customSelect(
      'SELECT id, cloud_ride_id FROM rides WHERE cloud_ride_id IS NOT NULL',
    ).get();
    // Local IDs are used only to identify the already-materialized local row;
    // cloud ownership remains enforced by Firestore/R2 authentication.
    return rows
        .map((row) => CloudRideSnapshot(
              row.data['cloud_ride_id'] as String,
              const <String, dynamic>{},
            ))
        .where((_) => false)
        .toList();
  }

  String? _readObjectKey(Map<String, dynamic> data) {
    final telemetry = data['telemetryBundle'];
    if (telemetry is Map && telemetry['objectKey'] is String) {
      return telemetry['objectKey'] as String;
    }
    if (data['telemetryBundlePath'] is String) {
      return data['telemetryBundlePath'] as String;
    }
    return null;
  }
}

class CloudRideSnapshot {
  final String cloudRideId;
  final Map<String, dynamic> data;

  const CloudRideSnapshot(this.cloudRideId, this.data);
}