// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:typed_data';

import 'package:json_rpc_2/json_rpc_2.dart' as json_rpc;
import 'package:vm_service/vm_service.dart';

import 'client.dart';
import 'dds_impl.dart';
import 'logging_repository.dart';
import 'rpc_error_codes.dart';
import 'utils/mutex.dart';

class StreamManager {
  StreamManager(this.dds);

  /// Send `streamNotify` notifications to clients subscribed to `streamId`.
  ///
  /// If `data` is of type `Uint8List`, the notification is assumed to be a
  /// binary event and is forwarded directly over the subscriber's websocket.
  /// Otherwise, the event is sent via the JSON RPC client.
  ///
  /// If `excludedClient` is provided, the notification will be sent to all
  /// clients subscribed to `streamId` except for `excludedClient`.
  void streamNotify(
    String streamId,
    data, {
    DartDevelopmentServiceClient? excludedClient,
  }) {
    if (streamListeners.containsKey(streamId)) {
      final listeners = streamListeners[streamId]!;
      final isBinaryData = data is Uint8List;
      for (final listener in listeners) {
        if (listener == excludedClient) {
          continue;
        }
        if (isBinaryData) {
          listener.connection.sink.add(data);
        } else {
          listener.sendNotification('streamNotify', data);
        }
      }
    }
  }

  static Map<String, dynamic> _buildStreamRegisteredEvent(
          String namespace, String service, String alias) =>
      {
        'streamId': kServiceStream,
        'event': {
          'type': 'Event',
          'kind': 'ServiceRegistered',
          'timestamp': DateTime.now().millisecondsSinceEpoch,
          'service': service,
          'method': '$namespace.$service',
          'alias': alias,
        }
      };

  void sendServiceRegisteredEvent(
    DartDevelopmentServiceClient client,
    String service,
    String alias,
  ) {
    final namespace = dds.getNamespace(client)!;
    streamNotify(
      kServiceStream,
      _buildStreamRegisteredEvent(namespace, service, alias),
      excludedClient: client,
    );
  }

  void _sendServiceUnregisteredEvents(
    DartDevelopmentServiceClient client,
  ) {
    final namespace = dds.getNamespace(client);
    for (final service in client.services.keys) {
      streamNotify(
        kServiceStream,
        {
          'streamId': kServiceStream,
          'event': {
            'type': 'Event',
            'kind': 'ServiceUnregistered',
            'timestamp': DateTime.now().millisecondsSinceEpoch,
            'service': service,
            'method': '$namespace.$service',
          },
        },
        excludedClient: client,
      );
    }
  }

  /// Start listening for `streamNotify` events from the VM service and forward
  /// them to the clients which have subscribed to the stream.
  Future<void> listen() async {
    // The IsolateManager requires information from both the Debug and
    // Isolate streams, so they must always be subscribed to by DDS.
    for (final stream in ddsCoreStreams) {
      try {
        await streamListen(null, stream);
        if (loggingRepositoryStreams.contains(stream)) {
          loggingRepositories[stream] = LoggingRepository();
        }
      } on json_rpc.RpcException {
        // Stdout and Stderr streams may not exist.
      }
    }
    dds.vmServiceClient.registerMethod(
      'streamNotify',
      (json_rpc.Parameters parameters) {
        final streamId = parameters['streamId'].asString;
        final event =
            Event.parse(parameters['event'].asMap.cast<String, dynamic>())!;
        final destinationStreamId =
            event.extensionData?.data[destinationStreamKey];

        if (destinationStreamId != null) {
          // Strip [destinationStreamKey] from the extension data so it is not
          // passed along.
          (parameters.value['event']['extensionData'] as Map<String, dynamic>)
              .remove(destinationStreamKey);
          if (destinationStreamId != kExtensionStream) {
            if (!customStreamListenerKeys.contains(destinationStreamId)) {
              // __destinationStream is only used by developer.postEvent.
              // developer.postEvent is only supposed to postEvents to the
              // Extension stream or to custom streams
              return;
            }
            final values = parameters.value;

            values['streamId'] = destinationStreamId;

            streamNotify(destinationStreamId, values);
            return;
          }
        }

        // Forward events from the streams IsolateManager subscribes to.
        if (isolateManagerStreams.contains(streamId)) {
          dds.isolateManager.handleIsolateEvent(event);
        }
        // Keep a history of messages to send to clients when they first
        // subscribe to a stream with an event history.
        if (loggingRepositories.containsKey(streamId)) {
          loggingRepositories[streamId]!.add(
            parameters.asMap.cast<String, dynamic>(),
          );
        }
        streamNotify(streamId, parameters.value);
      },
    );
  }

  /// Send an event to the [stream].
  ///
  /// [stream] must be a registered custom stream (i.e., not a stream specified
  /// as part of the VM service protocol).
  ///
  /// If [stream] is not a registered custom stream, an [RPCError] with code
  /// [kCustomStreamDoesNotExist] will be thrown.
  ///
  /// If [stream] is a core stream, an [RPCError] with code
  /// [kCoreStreamNotAllowed] will be thrown.
  void postEvent(
      String stream, String eventKind, Map<String, Object?> eventData) {
    if (coreStreams.contains(stream)) {
      throw kCoreStreamNotAllowed;
    }
    if (!customStreamListenerKeys.contains(stream)) {
      throw kCustomStreamDoesNotExist;
    }

    streamNotify(stream, <String, dynamic>{
      'streamId': stream,
      'event': {
        'type': 'Event',
        'kind': 'Extension',
        'timestamp': DateTime.now().millisecondsSinceEpoch,
        'extensionData': eventData,
        'extensionKind': eventKind,
      },
    });
  }

  /// Subscribes `client` to a stream.
  ///
  /// If `client` is the first client to listen to `stream`, DDS will send a
  /// `streamListen` request for `stream` to the VM service.
  Future<void> streamListen(
    DartDevelopmentServiceClient? client,
    String stream, {
    bool? includePrivates,
  }) async {
    // Weakly guard stream listening as it's safe to perform multiple listens
    // on a stream concurrently. However, cancelling streams while listening
    // to them concurrently can put things in a bad state. Use weak guarding to
    // improve latency of stream subscription.
    await _streamSubscriptionMutex.runGuardedWeak(
      () async {
        assert(stream.isNotEmpty);
        bool streamNewlySubscribed = false;
        if (!streamListeners.containsKey(stream)) {
          // Initialize the list of clients for the new stream before we do
          // anything else to ensure multiple clients registering for the same
          // stream in quick succession doesn't result in multiple streamListen
          // requests being sent to the VM service.
          streamNewlySubscribed = true;
          streamListeners[stream] = <DartDevelopmentServiceClient>[];
          if ((stream == kDebugStream && client == null) ||
              stream != kDebugStream) {
            // This will return an RPC exception if the stream doesn't exist. This
            // will throw and the exception will be forwarded to the client.
            try {
              final result =
                  await dds.vmServiceClient.sendRequest('streamListen', {
                'streamId': stream,
                if (includePrivates != null)
                  '_includePrivateMembers': includePrivates,
              });
              assert(result['type'] == 'Success');
            } on json_rpc.RpcException catch (e) {
              if (e.code == RpcErrorCodes.kInvalidParams) {
                // catching kInvalid params means that the vmServiceClient
                // does not know about the stream we passed. So assume that
                // the stream is a custom stream.
                customStreamListenerKeys.add(stream);
              } else {
                rethrow;
              }
            }
          }
        }
        if (streamListeners[stream]!.contains(client)) {
          throw kStreamAlreadySubscribedException;
        } else if (!streamNewlySubscribed && includePrivates != null) {
          // This private RPC might not be present. If it's not, we're communicating with an older
          // VM that doesn't support filtering private members, so they will always be included in
          // responses. Handle the method not found exception so the streamListen call doesn't
          // fail for older VMs.
          await dds.vmServiceClient.sendRequestAndIgnoreMethodNotFound(
              '_setStreamIncludePrivateMembers',
              {'streamId': stream, 'includePrivateMembers': includePrivates});
        }
        if (client != null) {
          streamListeners[stream]!.add(client);
          if (loggingRepositories.containsKey(stream)) {
            loggingRepositories[stream]!.sendHistoricalLogs(client);
          } else if (stream == kServiceStream) {
            // Send all previously registered service extensions when a client
            // subscribes to the Service stream.
            for (final c in dds.clientManager.clients) {
              if (c == client) {
                continue;
              }
              final namespace = dds.getNamespace(c);
              for (final service in c.services.keys) {
                client.sendNotification(
                  'streamNotify',
                  _buildStreamRegisteredEvent(
                    namespace!,
                    service,
                    c.services[service]!,
                  ),
                );
              }
            }
          }
        }
      },
    );
  }

  List<Map<String, dynamic>>? getStreamHistory(String stream) {
    if (!loggingRepositories.containsKey(stream)) {
      return null;
    }
    return [
      for (final event in loggingRepositories[stream]!()) event['event'],
    ];
  }

  /// Unsubscribes `client` from a stream.
  ///
  /// If `client` is the last client to unsubscribe from `stream`, DDS will
  /// send a `streamCancel` request for `stream` to the VM service.
  Future<void> streamCancel(
    DartDevelopmentServiceClient? client,
    String stream, {
    bool cancelCoreStream = false,
  }) async {
    await _streamSubscriptionMutex.runGuarded(
      () async {
        assert(stream.isNotEmpty);
        final listeners = streamListeners[stream];
        if (listeners == null ||
            client != null && !listeners.contains(client)) {
          throw kStreamNotSubscribedException;
        }

        if (customStreamListenerKeys.contains(stream)) {
          streamListeners[stream]!.remove(client);
          if (streamListeners[stream]!.isEmpty) {
            streamListeners.remove(stream);
          }
          return;
        }

        listeners.remove(client);
        // Don't cancel streams DDS needs to function.
        if (listeners.isEmpty &&
            (!ddsCoreStreams.contains(stream) || cancelCoreStream)) {
          streamListeners.remove(stream);
          // Ensure the VM service hasn't shutdown.
          if (dds.vmServiceClient.isClosed) {
            return;
          }
          final result = await dds.vmServiceClient.sendRequest('streamCancel', {
            'streamId': stream,
          });
          assert(result['type'] == 'Success');
        } else {
          streamListeners[stream] = listeners;
        }
      },
    );
  }

  /// Cleanup stream subscriptions for `client` when it has disconnected.
  void clientDisconnect(DartDevelopmentServiceClient client) {
    for (final streamId in streamListeners.keys.toList()) {
      streamCancel(client, streamId).catchError(
        (_) => null,
        // Ignore 'stream not subscribed' errors and StateErrors which arise
        // when DDS is shutting down.
        test: (e) => (e is json_rpc.RpcException) || (e is StateError),
      );
    }

    // Notify other service clients of service extensions that are being
    // unregistered.
    _sendServiceUnregisteredEvents(client);
  }

  static const kServiceStream = 'Service';

  static final kStreamAlreadySubscribedException =
      RpcErrorCodes.buildRpcException(
    RpcErrorCodes.kStreamAlreadySubscribed,
  );

  static final kStreamNotSubscribedException = RpcErrorCodes.buildRpcException(
    RpcErrorCodes.kStreamNotSubscribed,
  );

  static final kCustomStreamDoesNotExist = RpcErrorCodes.buildRpcException(
    RpcErrorCodes.kCustomStreamDoesNotExist,
  );
  static final kCoreStreamNotAllowed = RpcErrorCodes.buildRpcException(
    RpcErrorCodes.kCoreStreamNotAllowed,
  );

  static const kEchoStream = '_Echo';
  static const kDebugStream = 'Debug';
  static const kExtensionStream = 'Extension';
  static const kTimerStream = 'Timer';
  static const kHeapSnapshotStream = 'HeapSnapshot';
  static const kIsolateStream = 'Isolate';
  static const kGCStream = 'GC';
  static const kLoggingStream = 'Logging';
  static const kProfilerStream = 'Profiler';
  static const kStderrStream = 'Stderr';
  static const kStdoutStream = 'Stdout';
  static const kTimelineStream = 'Timeline';
  static const kVMStream = 'VM';

  static const destinationStreamKey = '__destinationStream';

  static const coreStreams = <String>[
    kEchoStream,
    kDebugStream,
    kExtensionStream,
    kHeapSnapshotStream,
    kIsolateStream,
    kGCStream,
    kLoggingStream,
    kStderrStream,
    kStdoutStream,
    kTimelineStream,
    kVMStream,
  ];

  static Map<String, LoggingRepository> loggingRepositories = {};

  // Never cancel the Debug or Isolate stream as `IsolateManager` requires
  // them for isolate state notifications.
  static const isolateManagerStreams = <String>{
    kDebugStream,
    kIsolateStream,
  };

  // Never cancel the logging, timer, and extension event streams as
  // `LoggingRepository` requires them keep history.
  static const loggingRepositoryStreams = <String>{
    kExtensionStream,
    kTimerStream,
    kLoggingStream,
    kStderrStream,
    kStdoutStream,
  };

  // The set of streams that DDS requires to function.
  static final ddsCoreStreams = <String>{
    ...isolateManagerStreams,
    ...loggingRepositoryStreams,
  };

  final DartDevelopmentServiceImpl dds;
  final streamListeners = <String, List<DartDevelopmentServiceClient>>{};
  final customStreamListenerKeys = <String>{};
  final _streamSubscriptionMutex = Mutex();
}