module.exports = class Maps {
  static and(...maps) {
    if (maps.length === 0) {
      return [];
    }

    const outputs = [];
    for (const i of maps) {
      outputs.push(new Map());
    }

    const [map1, ...rest] = maps;
    for (const k of map1.keys()) {
      if (rest.every((map) => map.has(k))) {
        for (let i = 0; i < maps.length; i++) {
          outputs[i].set(k, maps[i].get(k));
        }
      }
    }
    return outputs;
  }
  static combineBy(combineFn, ...maps) {
    const result = new Map();

    for (const map of maps) {
      for (const [k, v] of map.entries()) {
        result.set(k, result.has(k) ? combineFn(k, result.get(k), v) : v);
      }
    }

    return result;
  }
  static add(...maps) {
    return Maps.combineBy((k, v1, v2) => {
      return v1 + v2;
    }, ...maps);
  }
};