/**
 * Copyright 2017 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.
 */

/**
 * @template K, V
 */
class Multimap {
  constructor() {
    /** @type {!Map<K, !Set<!V>>} */
    this._map = new Map();
  }

  /**
   * @param {K} key
   * @param {V} value
   */
  set(key, value) {
    let set = this._map.get(key);
    if (!set) {
      set = new Set();
      this._map.set(key, set);
    }
    set.add(value);
  }

  /**
   * @param {K} key
   * @return {!Set<!V>}
   */
  get(key) {
    let result = this._map.get(key);
    if (!result)
      result = new Set();
    return result;
  }

  /**
   * @param {K} key
   * @return {boolean}
   */
  has(key) {
    return this._map.has(key);
  }

  /**
   * @param {K} key
   * @param {V} value
   * @return {boolean}
   */
  hasValue(key, value) {
    let set = this._map.get(key);
    if (!set)
      return false;
    return set.has(value);
  }

  /**
   * @return {number}
   */
  get size() {
    return this._map.size;
  }

  /**
   * @param {K} key
   * @param {V} value
   * @return {boolean}
   */
  delete(key, value) {
    let values = this.get(key);
    let result = values.delete(value);
    if (!values.size)
      this._map.delete(key);
    return result;
  }

  /**
   * @param {K} key
   */
  deleteAll(key) {
    this._map.delete(key);
  }

  /**
   * @return {!Array<K>}
   */
  keysArray() {
    return this._map.keysArray();
  }

  /**
   * @param {K} key
   * @return {?V} value
   */
  firstValue(key) {
    let set = this._map.get(key);
    if (!set)
      return null;
    return set.values().next().value;
  }

  /**
   * @return {K}
   */
  firstKey() {
    return this._map.keys().next().value;
  }

  /**
   * @return {!Array<!V>}
   */
  valuesArray() {
    let result = [];
    let keys = this.keysArray();
    for (let i = 0; i < keys.length; ++i)
      result.pushAll(this.get(keys[i]).valuesArray());
    return result;
  }

  clear() {
    this._map.clear();
  }
}

module.exports = Multimap;