import 'dart:async';
import 'sync_models.dart';

/// Explicit cloud confirmation states representing the exact verification status of a remote ride.
enum CloudConfirmationStatus {
  /// Firestore metadata and corresponding R2 bundle are consistently verified.
  confirmed,

  /// Required Firestore metadata or R2 object is absent.
  missing,

  /// Ride identity, owner, bundle reference, size, or checksum does not match.
  inconsistent,

  /// The current user cannot access or verify the ride.
  unauthorized,

  /// Network outage, timeout, rate limit, or transient backend failure.
  temporarilyUnverifiable,
}

/// Explicit verification report for a cloud ride.
class CloudConfirmationResult {
  final CloudConfirmationStatus status;
  final String? message;
  final String? remoteRideId;
  final String? ownerUid;
  final String? objectKey;
  final int? sizeBytes;
  final String? sha256;

  const CloudConfirmationResult({
    required this.status,
    this.message,
    this.remoteRideId,
    this.ownerUid,
    this.objectKey,
    this.sizeBytes,
    this.sha256,
  });

  const CloudConfirmationResult.confirmed({
    required String remoteRideId,
    String? ownerUid,
    String? objectKey,
    int? sizeBytes,
    String? sha256,
    String? message,
  }) : this(
         status: CloudConfirmationStatus.confirmed,
         remoteRideId: remoteRideId,
         ownerUid: ownerUid,
         objectKey: objectKey,
         sizeBytes: sizeBytes,
         sha256: sha256,
         message: message,
       );

  const CloudConfirmationResult.missing({
    required String remoteRideId,
    String? message,
  }) : this(
         status: CloudConfirmationStatus.missing,
         remoteRideId: remoteRideId,
         message: message,
       );

  const CloudConfirmationResult.inconsistent({
    required String remoteRideId,
    String? ownerUid,
    String? objectKey,
    String? message,
  }) : this(
         status: CloudConfirmationStatus.inconsistent,
         remoteRideId: remoteRideId,
         ownerUid: ownerUid,
         objectKey: objectKey,
         message: message,
       );

  const CloudConfirmationResult.unauthorized({
    required String remoteRideId,
    String? ownerUid,
    String? message,
  }) : this(
         status: CloudConfirmationStatus.unauthorized,
         remoteRideId: remoteRideId,
         ownerUid: ownerUid,
         message: message,
       );

  const CloudConfirmationResult.temporarilyUnverifiable({
    required String remoteRideId,
    String? message,
  }) : this(
         status: CloudConfirmationStatus.temporarilyUnverifiable,
         remoteRideId: remoteRideId,
         message: message,
       );

  bool get isConfirmed => status == CloudConfirmationStatus.confirmed;
  bool get isMissing => status == CloudConfirmationStatus.missing;
  bool get isInconsistent => status == CloudConfirmationStatus.inconsistent;
  bool get isUnauthorized => status == CloudConfirmationStatus.unauthorized;
  bool get isTemporarilyUnverifiable =>
      status == CloudConfirmationStatus.temporarilyUnverifiable;

  @override
  String toString() =>
      'CloudConfirmationResult(status: $status, ride: $remoteRideId, owner: $ownerUid, message: $message)';
}

/// Abstract contract for synchronization providers (e.g. Firebase, GitHub, Supabase).
/// Implementations must not leak provider-specific SDK types into the core sync engine.
abstract class SyncProvider {
  /// Unique identifier of the provider (e.g. 'firebase', 'github', 'fake')
  String get providerId;

  /// Whether the provider backend and network are currently available
  Future<bool> isAvailable();

  /// Whether this provider requires an active user authentication credential
  Future<bool> requiresAuthentication();

  /// Performs the upload of the local ride referenced by [item].
  /// Must return a deterministic [SyncResult].
  Future<SyncResult> uploadRide(SyncItem item);

  /// Checks if the ride with [remoteRideId] is already confirmed uploaded in the cloud.
  /// Backward compatible wrapper around [verifyCloudConfirmation].
  Future<bool> isRideConfirmedInCloud(String remoteRideId) async {
    final result = await verifyCloudConfirmation(remoteRideId);
    return result.isConfirmed;
  }

  /// Deeply verifies whether [remoteRideId] is confirmed and recoverable in the cloud.
  /// Default implementation returns [CloudConfirmationStatus.missing].
  Future<CloudConfirmationResult> verifyCloudConfirmation(
    String remoteRideId,
  ) async => CloudConfirmationResult.missing(remoteRideId: remoteRideId);
}

/// Simulated behavior modes for testing the synchronization engine deterministically
enum FakeSyncBehavior {
  success,
  temporaryFailure,
  permanentFailure,
  authRequired,
  offline,
}

/// Deterministic, in-memory fake synchronization provider for testing
class FakeSyncProvider implements SyncProvider {
  @override
  final String providerId;

  FakeSyncBehavior behavior;
  int delayMs;
  final List<SyncItem> uploadedItems = [];
  final Map<int, int> uploadAttemptsPerRide = {};
  final Set<String> confirmedRemoteRideIds = {};
  final Map<String, CloudConfirmationResult> confirmationResults = {};

  FakeSyncProvider({
    this.providerId = 'fake',
    this.behavior = FakeSyncBehavior.success,
    this.delayMs = 0,
  });

  @override
  Future<bool> isAvailable() async {
    if (behavior == FakeSyncBehavior.offline) return false;
    return true;
  }

  @override
  Future<bool> requiresAuthentication() async {
    return behavior == FakeSyncBehavior.authRequired;
  }

  @override
  Future<bool> isRideConfirmedInCloud(String remoteRideId) async {
    final result = await verifyCloudConfirmation(remoteRideId);
    return result.isConfirmed;
  }

  @override
  Future<CloudConfirmationResult> verifyCloudConfirmation(
    String remoteRideId,
  ) async {
    if (confirmationResults.containsKey(remoteRideId)) {
      return confirmationResults[remoteRideId]!;
    }
    if (confirmedRemoteRideIds.contains(remoteRideId)) {
      return CloudConfirmationResult.confirmed(remoteRideId: remoteRideId);
    }
    if (behavior == FakeSyncBehavior.offline ||
        behavior == FakeSyncBehavior.temporaryFailure) {
      return CloudConfirmationResult.temporarilyUnverifiable(
        remoteRideId: remoteRideId,
        message: 'Fake provider backend unavailable',
      );
    }
    if (behavior == FakeSyncBehavior.authRequired) {
      return CloudConfirmationResult.unauthorized(
        remoteRideId: remoteRideId,
        message: 'Fake provider requires authentication',
      );
    }
    return CloudConfirmationResult.missing(
      remoteRideId: remoteRideId,
      message: 'Ride not found in fake provider',
    );
  }

  @override
  Future<SyncResult> uploadRide(SyncItem item) async {
    if (delayMs > 0) {
      await Future<void>.delayed(Duration(milliseconds: delayMs));
    }

    uploadAttemptsPerRide[item.localRideId] =
        (uploadAttemptsPerRide[item.localRideId] ?? 0) + 1;

    switch (behavior) {
      case FakeSyncBehavior.success:
        uploadedItems.add(item);
        final remoteId =
            'remote_${item.localRideId}_${DateTime.now().millisecondsSinceEpoch}';
        confirmedRemoteRideIds.add(remoteId);
        confirmationResults[remoteId] = CloudConfirmationResult.confirmed(
          remoteRideId: remoteId,
        );
        return SyncResult.success(remoteId: remoteId);

      case FakeSyncBehavior.temporaryFailure:
        return SyncResult.temporaryFailure(
          'Simulated temporary network/server error (HTTP 503)',
        );

      case FakeSyncBehavior.permanentFailure:
        return SyncResult.permanentFailure(
          'Simulated unrecoverable payload or validation error (HTTP 422)',
        );

      case FakeSyncBehavior.authRequired:
        return SyncResult.authRequired(
          message: 'Simulated authentication expired or required (HTTP 401)',
        );

      case FakeSyncBehavior.offline:
        return SyncResult.temporaryFailure(
          'Simulated offline network unreachable',
        );
    }
  }

  void reset() {
    uploadedItems.clear();
    uploadAttemptsPerRide.clear();
    confirmedRemoteRideIds.clear();
    confirmationResults.clear();
  }
}