// 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.

library observable.src.to_observable;

import 'dart:collection';

import 'observable.dart' show Observable;
import 'collections.dart' show ObservableList, ObservableMap;

/// Converts the [Iterable] or [Map] to an [ObservableList] or [ObservableMap],
/// respectively. This is a convenience function to make it easier to convert
/// literals into the corresponding observable collection type.
///
/// If [value] is not one of those collection types, or is already [Observable],
/// it will be returned unmodified.
///
/// If [value] is a [Map], the resulting value will use the appropriate kind of
/// backing map: either [HashMap], [LinkedHashMap], or [SplayTreeMap].
///
/// By default this performs a deep conversion, but you can set [deep] to false
/// for a shallow conversion. This does not handle circular data structures.
/// If a conversion is peformed, mutations are only observed to the result of
/// this function. Changing the original collection will not affect it.
// TODO(jmesserly): ObservableSet?
toObservable(dynamic value, {bool deep: true}) =>
    deep ? _toObservableDeep(value) : _toObservableShallow(value);

dynamic _toObservableShallow(dynamic value) {
  if (value is Observable) return value;
  if (value is Map) return new ObservableMap.from(value);
  if (value is Iterable) return new ObservableList.from(value);
  return value;
}

dynamic _toObservableDeep(dynamic value) {
  if (value is Observable) return value;
  if (value is Map) {
    var result = new ObservableMap.createFromType(value);
    value.forEach((k, v) {
      result[_toObservableDeep(k)] = _toObservableDeep(v);
    });
    return result;
  }
  if (value is Iterable) {
    return new ObservableList.from(value.map(_toObservableDeep));
  }
  return value;
}