lib/src/worker/worker_connection.dart

// Copyright (c) 2016, 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:async';
import 'dart:io';

import '../async_message_grouper.dart';
import '../sync_message_grouper.dart';
import '../utils.dart';
import '../worker_protocol.pb.dart';

/// A connection from a worker to a driver (driver could be bazel, a dart
/// program using `BazelWorkerDriver`, or any other process that speaks the
/// protocol).
abstract class WorkerConnection {
  /// Reads a [WorkRequest] or returns [null] if there are none left.
  ///
  /// See [AsyncWorkerConnection] and [SyncWorkerConnection] for more narrow
  /// interfaces.
  FutureOr<WorkRequest> readRequest();

  void writeResponse(WorkResponse response);
}

abstract class AsyncWorkerConnection implements WorkerConnection {
  @override
  Future<WorkRequest> readRequest();
}

abstract class SyncWorkerConnection implements WorkerConnection {
  WorkRequest readRequest();
}

/// Default implementation of [AsyncWorkerConnection] that works with [Stdin]
/// and [Stdout].
class StdAsyncWorkerConnection implements AsyncWorkerConnection {
  final AsyncMessageGrouper _messageGrouper;
  final StreamSink<List<int>> _outputStream;

  StdAsyncWorkerConnection(
      {Stream<List<int>> inputStream, StreamSink<List<int>> outputStream})
      : _messageGrouper = new AsyncMessageGrouper(inputStream ?? stdin),
        _outputStream = outputStream ?? stdout;

  @override
  Future<WorkRequest> readRequest() async {
    var buffer = await _messageGrouper.next;
    if (buffer == null) return null;

    return new WorkRequest.fromBuffer(buffer);
  }

  @override
  void writeResponse(WorkResponse response) {
    _outputStream.add(protoToDelimitedBuffer(response));
  }
}

/// Default implementation of [SyncWorkerConnection] that works with [Stdin] and
/// [Stdout].
class StdSyncWorkerConnection implements SyncWorkerConnection {
  final SyncMessageGrouper _messageGrouper;
  final Stdout _stdoutStream;

  StdSyncWorkerConnection({Stdin stdinStream, Stdout stdoutStream})
      : _messageGrouper = new SyncMessageGrouper(stdinStream ?? stdin),
        _stdoutStream = stdoutStream ?? stdout;

  @override
  WorkRequest readRequest() {
    var buffer = _messageGrouper.next;
    if (buffer == null) return null;

    return new WorkRequest.fromBuffer(buffer);
  }

  @override
  void writeResponse(WorkResponse response) {
    _stdoutStream.add(protoToDelimitedBuffer(response));
  }
}