using System;
using System.Collections.Generic;

namespace PDFPatcher.Common
{
	public class DualKeyDictionary<K, V> : IDictionary<K, V>
	{
		private readonly Dictionary<K, V> _keyDictionary = new Dictionary<K, V>();
		private readonly Dictionary<V, K> _reverseDictionary = new Dictionary<V, K>();

		public DualKeyDictionary() {

		}

		public K GetKeyByValue(V value) {
			return _reverseDictionary[value];
		}

		#region IDictionary<K,V> 成员

		public void Add(K key, V value) {
			_keyDictionary.Add(key, value);
			_reverseDictionary.Add(value, key);
		}

		public bool ContainsKey(K key) {
			return _keyDictionary.ContainsKey(key);
		}
		public bool ContainsValue(V value) {
			return _reverseDictionary.ContainsKey(value);
		}

		public ICollection<K> Keys => _keyDictionary.Keys;

		public bool Remove(K key) {
			if (_keyDictionary.ContainsKey(key) == false) {
				return false;
			}
			var value = _keyDictionary[key];
			_keyDictionary.Remove(key);
			_reverseDictionary.Remove(value);
			return true;
		}

		public bool TryGetValue(K key, out V value) {
			return TryGetValue(key, out value);
		}

		public ICollection<V> Values => _reverseDictionary.Keys;

		public V this[K key] {
			get => _keyDictionary[key];
			set {
				Remove(key);
				Add(key, value);
			}
		}

		#endregion

		#region ICollection<KeyValuePair<K,V>> 成员

		public void Add(KeyValuePair<K, V> item) {
			Add(item.Key, item.Value);
		}

		public void Clear() {
			_keyDictionary.Clear();
			_reverseDictionary.Clear();
		}

		public bool Contains(KeyValuePair<K, V> item) {
			return _keyDictionary.ContainsKey(item.Key) && _reverseDictionary.ContainsKey(item.Value);
		}

		public void CopyTo(KeyValuePair<K, V>[] array, int arrayIndex) {
			((ICollection<KeyValuePair<K, V>>)_keyDictionary).CopyTo(array, arrayIndex);
		}

		public int Count => _keyDictionary.Count;

		public bool IsReadOnly => false;

		public bool Remove(KeyValuePair<K, V> item) {
			return Remove(item.Key);
		}

		#endregion

		#region IEnumerable<KeyValuePair<K,V>> 成员

		public IEnumerator<KeyValuePair<K, V>> GetEnumerator() {
			return ((IEnumerable<KeyValuePair<K, V>>)_keyDictionary).GetEnumerator();
		}

		#endregion

		#region IEnumerable 成员

		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
			return ((System.Collections.IEnumerable)_keyDictionary).GetEnumerator();
		}

		#endregion
	}
}