// Copyright (c) 2011, 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.

/**
 * Provides a Map abstraction on top of data-* attributes, similar to the
 * dataSet in the old DOM.
 */
class _DataAttributeMap implements AttributeMap {

  final Map<String, String> _attributes;

  _DataAttributeMap(this._attributes);

  // interface Map

  // TODO: Use lazy iterator when it is available on Map.
  bool containsValue(String value) => getValues().some((v) => v == value);

  bool containsKey(String key) => _attributes.containsKey(_attr(key));

  String operator [](String key) => _attributes[_attr(key)];

  void operator []=(String key, value) {
    _attributes[_attr(key)] = '$value';
  }

  String putIfAbsent(String key, String ifAbsent()) {
    if (!containsKey(key)) {
      return this[key] = ifAbsent();
    }
    return this[key];
  }

  String remove(String key) => _attributes.remove(_attr(key));

  void clear() {
    // Needs to operate on a snapshot since we are mutatiting the collection.
    for (String key in getKeys()) {
      remove(key);
    }
  }

  void forEach(void f(String key, String value)) {
    _attributes.forEach((String key, String value) {
      if (_matches(key)) {
        f(_strip(key), value);
      }
    });
  }

  Collection<String> getKeys() {
    final keys = new List<String>();
    _attributes.forEach((String key, String value) {
      if (_matches(key)) {
        keys.add(_strip(key));
      }
    });
    return keys;
  }

  Collection<String> getValues() {
    final values = new List<String>();
    _attributes.forEach((String key, String value) {
      if (_matches(key)) {
        values.add(value);
      }
    });
    return values;
  }

  int get length() => getKeys().length;

  // TODO: Use lazy iterator when it is available on Map.
  bool isEmpty() => length == 0;

  // Helpers.
  String _attr(String key) => 'data-$key';
  bool _matches(String key) => key.startsWith('data-');
  String _strip(String key) => key.substring(5);
}