bluetooth_descriptor.dart

// Copyright 2017, Paul DeMarco.
// All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of flutter_blue_plus;

class BluetoothDescriptor
{
    static final Guid cccd = Guid("00002902-0000-1000-8000-00805f9b34fb");

    final Guid uuid;
    final DeviceIdentifier deviceId;
    final Guid serviceUuid;
    final Guid characteristicUuid;

    final _BehaviorSubject<List<int>> _value;
      
    Stream<List<int>> get value => _value.stream;

    List<int> get lastValue => _value.latestValue;

    final _Mutex _readWriteMutex = _Mutex();

    BluetoothDescriptor.fromProto(protos.BluetoothDescriptor p)
        : uuid = Guid(p.uuid),
        deviceId = DeviceIdentifier(p.remoteId),
        serviceUuid = Guid(p.serviceUuid),
        characteristicUuid = Guid(p.characteristicUuid),
        _value = _BehaviorSubject(p.value);

    /// Retrieves the value of a specified descriptor
    Future<List<int>> read() async
    {
        List<int> readValue = [];

        // Only allow a single read or write operation
        // at a time, to prevent race conditions.
        await _readWriteMutex.synchronized(() async {

            var request = protos.ReadDescriptorRequest.create()
            ..remoteId = deviceId.toString()
            ..descriptorUuid = uuid.toString()
            ..characteristicUuid = characteristicUuid.toString()
            ..serviceUuid = serviceUuid.toString();

            Stream<protos.ReadDescriptorResponse> responseStream = FlutterBluePlus.instance._methodStream
                .where((m) => m.method == "ReadDescriptorResponse")
                .map((m) => m.arguments)
                .map((buffer) => protos.ReadDescriptorResponse.fromBuffer(buffer))
                .where((p) =>
                    (p.request.remoteId == request.remoteId) &&
                    (p.request.descriptorUuid == request.descriptorUuid) &&
                    (p.request.characteristicUuid == request.characteristicUuid) &&
                    (p.request.serviceUuid == request.serviceUuid));

            // Start listening now, before invokeMethod, to ensure we don't miss the response
            Future<protos.ReadDescriptorResponse> futureResponse = responseStream.first;

            await FlutterBluePlus.instance._channel
                .invokeMethod('readDescriptor', request.writeToBuffer());

            protos.ReadDescriptorResponse response = await futureResponse;

            readValue = response.value;

            _value.add(readValue);
        });

        return readValue;
    }


    /// Writes the value of a descriptor
    Future<void> write(List<int> value) async
    {
        // Only allow a single read or write operation
        // at a time, to prevent race conditions.
        await _readWriteMutex.synchronized(() async {

            var request = protos.WriteDescriptorRequest.create()
            ..remoteId = deviceId.toString()
            ..descriptorUuid = uuid.toString()
            ..characteristicUuid = characteristicUuid.toString()
            ..serviceUuid = serviceUuid.toString()
            ..value = value;

            Stream<protos.WriteDescriptorResponse> responseStream = FlutterBluePlus.instance._methodStream
                .where((m) => m.method == "WriteDescriptorResponse")
                .map((m) => m.arguments)
                .map((buffer) => protos.WriteDescriptorResponse.fromBuffer(buffer))
                .where((p) =>
                    (p.request.remoteId == request.remoteId) &&
                    (p.request.descriptorUuid == request.descriptorUuid) &&
                    (p.request.characteristicUuid == request.characteristicUuid) &&
                    (p.request.serviceUuid == request.serviceUuid));

            // Start listening now, before invokeMethod, to ensure we don't miss the response
            Future<protos.WriteDescriptorResponse> futureResponse = responseStream.first;

            await FlutterBluePlus.instance._channel
                .invokeMethod('writeDescriptor', request.writeToBuffer());

            protos.WriteDescriptorResponse response = await futureResponse;

            if (!response.success) {
                throw Exception('Failed to write the descriptor');
            }

            _value.add(value);
        });

        return Future.value();
    }


    @override
    String toString()
    {
        return 'BluetoothDescriptor{'
        'uuid: $uuid, '
        'deviceId: $deviceId, '
        'serviceUuid: $serviceUuid, '
        'characteristicUuid: $characteristicUuid, '
        'value: ${_value.value}'
        '}';
    }
}