import 'package:dartz/dartz.dart';
import '../../core/errors/exceptions.dart';
import '../../core/errors/failures.dart';
import '../data_sources/local/server_local_data_source.dart';
import '../data_sources/remote/server_remote_data_source.dart';
import '../data_sources/local/action_mapping_local_data_source.dart';
import '../data_sources/remote/action_mapping_remote_data_source.dart';

enum SyncStatus {
  idle,
  syncing,
  success,
  error,
}

class SyncResult {
  final SyncStatus status;
  final String? message;
  final int? syncedCount;
  final List<String>? errors;

  SyncResult({
    required this.status,
    this.message,
    this.syncedCount,
    this.errors,
  });

  factory SyncResult.idle() => SyncResult(status: SyncStatus.idle);

  factory SyncResult.syncing() => SyncResult(
        status: SyncStatus.syncing,
        message: 'Syncing changes...',
      );

  factory SyncResult.success(int count) => SyncResult(
        status: SyncStatus.success,
        message: 'Successfully synced $count change${count != 1 ? 's' : ''}',
        syncedCount: count,
      );

  factory SyncResult.error(List<String> errors) => SyncResult(
        status: SyncStatus.error,
        message: 'Sync failed: ${errors.length} error${errors.length != 1 ? 's' : ''}',
        errors: errors,
      );
}

abstract class SyncService {
  /// Sync all dirty servers with the remote API
  Future<Either<Failure, SyncResult>> syncServers();

  /// Download fresh data from server and update local storage
  Future<Either<Failure, int>> downloadServers();

  /// Sync all dirty action mappings with the remote API
  Future<Either<Failure, SyncResult>> syncActionMappings();

  /// Download fresh action mappings from server and update local storage
  Future<Either<Failure, int>> downloadActionMappings();
}

class SyncServiceImpl implements SyncService {
  final ServerLocalDataSource localDataSource;
  final ServerRemoteDataSource remoteDataSource;
  final ActionMappingLocalDataSource actionMappingLocalDataSource;
  final ActionMappingRemoteDataSource actionMappingRemoteDataSource;

  SyncServiceImpl({
    required this.localDataSource,
    required this.remoteDataSource,
    required this.actionMappingLocalDataSource,
    required this.actionMappingRemoteDataSource,
  });

  @override
  Future<Either<Failure, SyncResult>> syncServers() async {
    try {
      // Get all dirty servers
      final dirtyServers = await localDataSource.getDirtyServers();

      if (dirtyServers.isEmpty) {
        return Right(SyncResult.success(0));
      }

      final errors = <String>[];
      int successCount = 0;

      // Process each dirty server
      for (final server in dirtyServers) {
        try {
          final operation = server.syncOperation;
          final serverModel = server.toServerModel();

          if (operation == 'create') {
            await remoteDataSource.createServer(serverModel);
            await localDataSource.markServerAsSynced(server.id, server.serverType);
            successCount++;
          } else if (operation == 'update') {
            await remoteDataSource.updateServer(serverModel);
            await localDataSource.markServerAsSynced(server.id, server.serverType);
            successCount++;
          } else if (operation == 'delete') {
            await remoteDataSource.deleteServer(server.id, server.serverType);
            await localDataSource.markServerAsSynced(server.id, server.serverType);
            successCount++;
          }
        } catch (e) {
          errors.add('Failed to sync ${server.alias}: ${e.toString()}');
        }
      }

      if (errors.isEmpty) {
        return Right(SyncResult.success(successCount));
      } else if (successCount > 0) {
        // Partial success
        return Right(SyncResult(
          status: SyncStatus.success,
          message: 'Synced $successCount/${dirtyServers.length} changes',
          syncedCount: successCount,
          errors: errors,
        ));
      } else {
        // Complete failure
        return Right(SyncResult.error(errors));
      }
    } on ServerException catch (e) {
      return Left(ServerFailure(e.message));
    } on NetworkException catch (e) {
      return Left(NetworkFailure(e.message));
    } catch (e) {
      return Left(ServerFailure('Unexpected error during sync: ${e.toString()}'));
    }
  }

  @override
  Future<Either<Failure, int>> downloadServers() async {
    try {
      // Fetch all servers from API
      final servers = await remoteDataSource.getAllServers();

      // Replace local storage (preserving dirty servers)
      await localDataSource.replaceAllServers(servers);

      return Right(servers.length);
    } on ServerException catch (e) {
      return Left(ServerFailure(e.message));
    } on NetworkException catch (e) {
      return Left(NetworkFailure(e.message));
    } catch (e) {
      return Left(ServerFailure('Unexpected error during download: ${e.toString()}'));
    }
  }

  @override
  Future<Either<Failure, SyncResult>> syncActionMappings() async {
    try {
      // Get all dirty action mappings
      final dirtyMappings = await actionMappingLocalDataSource.getDirtyActionMappings();

      if (dirtyMappings.isEmpty) {
        return Right(SyncResult.success(0));
      }

      final errors = <String>[];
      int successCount = 0;

      // Process each dirty action mapping
      for (final mapping in dirtyMappings) {
        try {
          final operation = mapping.syncOperation;
          final mappingModel = mapping.toActionMappingModel();

          if (operation == 'create') {
            await actionMappingRemoteDataSource.createActionMapping(mappingModel);
            await actionMappingLocalDataSource.markActionMappingAsSynced(mapping.id);
            successCount++;
          } else if (operation == 'update') {
            await actionMappingRemoteDataSource.updateActionMapping(mapping.id, mappingModel);
            await actionMappingLocalDataSource.markActionMappingAsSynced(mapping.id);
            successCount++;
          } else if (operation == 'delete') {
            await actionMappingRemoteDataSource.deleteActionMapping(mapping.id);
            await actionMappingLocalDataSource.markActionMappingAsSynced(mapping.id);
            successCount++;
          }
        } catch (e) {
          errors.add('Failed to sync ${mapping.name}: ${e.toString()}');
        }
      }

      if (errors.isEmpty) {
        return Right(SyncResult.success(successCount));
      } else if (successCount > 0) {
        // Partial success
        return Right(SyncResult(
          status: SyncStatus.success,
          message: 'Synced $successCount/${dirtyMappings.length} changes',
          syncedCount: successCount,
          errors: errors,
        ));
      } else {
        // Complete failure
        return Right(SyncResult.error(errors));
      }
    } on ActionMappingException catch (e) {
      return Left(ActionMappingFailure(e.message));
    } on NetworkException catch (e) {
      return Left(NetworkFailure(e.message));
    } catch (e) {
      return Left(ActionMappingFailure('Unexpected error during sync: ${e.toString()}'));
    }
  }

  @override
  Future<Either<Failure, int>> downloadActionMappings() async {
    try {
      // Fetch all action mappings from API
      final mappings = await actionMappingRemoteDataSource.getAllActionMappings();

      // Replace local storage with force=true to discard local changes and get fresh server data
      await actionMappingLocalDataSource.replaceAllActionMappings(mappings, force: true);

      return Right(mappings.length);
    } on ActionMappingException catch (e) {
      return Left(ActionMappingFailure(e.message));
    } on NetworkException catch (e) {
      return Left(NetworkFailure(e.message));
    } catch (e) {
      return Left(ActionMappingFailure('Unexpected error during download: ${e.toString()}'));
    }
  }
}