pkg/json_rpc_2/lib/src/utils.dart

// Copyright (c) 2014, 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.

library json_rpc_2.utils;

import 'dart:async';

import 'package:stack_trace/stack_trace.dart';

typedef ZeroArgumentFunction();

/// Like [new Future.sync], but automatically wraps the future in a
/// [Chain.track] call.
Future syncFuture(callback()) => Chain.track(new Future.sync(callback));

/// Returns a sentence fragment listing the elements of [iter].
///
/// This converts each element of [iter] to a string and separates them with
/// commas and/or "and" where appropriate.
String toSentence(Iterable iter) {
  if (iter.length == 1) return iter.first.toString();
  return iter.take(iter.length - 1).join(", ") + " and ${iter.last}";
}

/// Returns [name] if [number] is 1, or the plural of [name] otherwise.
///
/// By default, this just adds "s" to the end of [name] to get the plural. If
/// [plural] is passed, that's used instead.
String pluralize(String name, int number, {String plural}) {
  if (number == 1) return name;
  if (plural != null) return plural;
  return '${name}s';
}

/// A regular expression to match the exception prefix that some exceptions'
/// [Object.toString] values contain.
final _exceptionPrefix = new RegExp(r'^([A-Z][a-zA-Z]*)?(Exception|Error): ');

/// Get a string description of an exception.
///
/// Many exceptions include the exception class name at the beginning of their
/// [toString], so we remove that if it exists.
String getErrorMessage(error) =>
    error.toString().replaceFirst(_exceptionPrefix, '');

/// Returns a [StreamSink] that wraps [sink] and maps each event added using
/// [callback].
StreamSink mapStreamSink(StreamSink sink, callback(event)) =>
    new _MappedStreamSink(sink, callback);

/// A [StreamSink] wrapper that maps each event added to the sink.
class _MappedStreamSink implements StreamSink {
  final StreamSink _inner;
  final Function _callback;

  Future get done => _inner.done;

  _MappedStreamSink(this._inner, this._callback);

  void add(event) => _inner.add(_callback(event));
  void addError(error, [StackTrace stackTrace]) =>
      _inner.addError(error, stackTrace);
  Future addStream(Stream stream) => _inner.addStream(stream.map(_callback));
  Future close() => _inner.close();
}