// 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 'package:dart_internal/extract_type_arguments.dart';

import 'observable.dart' show Observable;
import 'observable_list.dart' show ObservableList;
import 'observable_map.dart' show 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 extractMapTypeArguments(
        value, <K, V>() => new ObservableMap<K, V>.from(value));
  }

  if (value is Iterable) {
    return extractIterableTypeArgument(
        value, <T>() => new ObservableList<T>.from(value));
  }

  return value;
}

dynamic _toObservableDeep(dynamic value) {
  if (value is Observable) return value;

  if (value is Map) {
    return extractMapTypeArguments(value, <K, V>() {
      var result = new ObservableMap<K, V>.createFromType(value);
      value.forEach((k, v) {
        result[_toObservableDeep(k)] = _toObservableDeep(v);
      });
      return result;
    });
  }

  if (value is Iterable) {
    return extractIterableTypeArgument(value, <T>() {
      var result = new ObservableList<T>();
      for (var element in value) {
        result.add(_toObservableDeep(element));
      }
      return result;
    });
  }

  return value;
}