import 'dart:collection';

typedef EvictionHandler<K, V>(K key, V value);

class LRUMap<K, V> {
  final LinkedHashMap<K, V> _map = new LinkedHashMap<K, V>();
  final int _maxSize;
  final EvictionHandler<K, V> _handler;

  LRUMap(this._maxSize, [this._handler]);

  V get(K key) {
    V value = _map.remove(key);
    if (value != null) {
      _map[key] = value;
    }
    return value;
  }

  void put(K key, V value) {
    _map.remove(key);
    _map[key] = value;
    if (_map.length > _maxSize) {
      K evictedKey = _map.keys.first;
      V evictedValue = _map.remove(evictedKey);
      if (_handler != null) {
        _handler(evictedKey, evictedValue);
      }
    }
  }

  void remove(K key) {
    _map.remove(key);
  }
}