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quiver/lib/src/collection/bimap.dart

-// Copyright 2013 Google Inc. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-part of quiver.collection;
-
-/**
- * A bi-directional map whose key-value pairs form a one-to-one correspondence.
- * BiMaps support an `inverse` property which gives access to an inverted view
- * of the map, such that there is a mapping (v, k) for each pair (k, v) in the
- * original map. Since a one-to-one key-value invariant applies, it is an error
- * to insert duplicate values into this map. It is also an error to insert null
- * keys or values into this map.
- */
-abstract class BiMap<K, V> implements Map<K, V> {
-  /**
-   * Creates a BiMap instance with the default implementation.
-   */
-  factory BiMap() => new HashBiMap();
-
-  /**
-   * Adds an association between key and value.
-   *
-   * Throws [ArgumentError] if an association involving [value] exists in the
-   * map; otherwise, the association is inserted, overwriting any existing
-   * association for the key.
-   */
-  void operator []=(K key, V value);
-
-  /**
-   * Replaces any existing associations(s) involving key and value.
-   *
-   * If an association involving [key] or [value] exists in the map, it is
-   * removed.
-   */
-  void replace(K key, V value);
-
-  /**
-   * Returns the inverse of this map, with key-value pairs (v, k) for each
-   * pair (k, v) in this map.
-   */
-  BiMap<V, K> get inverse;
-}
-
-/**
- * A hash-table based implementation of BiMap.
- */
-class HashBiMap<K, V> implements BiMap<K, V> {
-  final Map<K, V> _map;
-  final Map<V, K> _inverse;
-  BiMap<V, K> _cached;
-
-  HashBiMap() : this._from(new HashMap(), new HashMap());
-  HashBiMap._from(this._map, this._inverse);
-
-  V operator [](Object key) => _map[key];
-  void operator []=(K key, V value) {
-    _add(key, value, false);
-  }
-  void replace(K key, V value) {
-    _add(key, value, true);
-  }
-  void addAll(Map<K, V> other) => other.forEach((k, v) => _add(k, v, false));
-  bool containsKey(Object key) => _map.containsKey(key);
-  bool containsValue(Object value) => _inverse.containsKey(value);
-  void forEach(void f(K key, V value)) => _map.forEach(f);
-  bool get isEmpty => _map.isEmpty;
-  bool get isNotEmpty => _map.isNotEmpty;
-  Iterable<K> get keys => _map.keys;
-  int get length => _map.length;
-  Iterable<V> get values => _inverse.keys;
-
-  BiMap<V, K> get inverse {
-    if (_cached == null) {
-      _cached = new HashBiMap._from(_inverse, _map);
-    }
-    return _cached;
-  }
-
-  V putIfAbsent(K key, V ifAbsent()) {
-    var value = _map[key];
-    if (value != null) return value;
-    if (!_map.containsKey(key)) return _add(key, ifAbsent(), false);
-    return null;
-  }
-
-  V remove(Object key) {
-    _inverse.remove(_map[key]);
-    return _map.remove(key);
-  }
-
-  void clear() {
-    _map.clear();
-    _inverse.clear();
-  }
-
-  V _add(K key, V value, bool replace) {
-    if (key == null) throw new ArgumentError("null key");
-    if (value == null) throw new ArgumentError("null value");
-    var oldValue = _map[key];
-    if (oldValue == value) return value;
-    if (_inverse.containsKey(value)) {
-      if (!replace) throw new ArgumentError("Mapping for $value exists");
-      _map.remove(_inverse[value]);
-    }
-    _inverse.remove(oldValue);
-    _map[key] = value;
-    _inverse[value] = key;
-    return value;
-  }
-}