'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.Semaphore = undefined;
exports.ncpAsync = ncpAsync;

var _ncp;

function _load_ncp() {
  return _ncp = _interopRequireDefault(require('ncp'));
}

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _asyncToGenerator(fn) { return function () { var gen = fn.apply(this, arguments); return new Promise(function (resolve, reject) { function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { return Promise.resolve(value).then(function (value) { step("next", value); }, function (err) { step("throw", err); }); } } return step("next"); }); }; }

function ncpAsync(source, dest, options = {}) {
  return new Promise((resolve, reject) => {
    (0, (_ncp || _load_ncp()).default)(source, dest, options, err => {
      if (err) {
        reject(err);
      } else {
        resolve();
      }
    });
  });
}

class Semaphore {
  constructor() {
    this.queue = [];
    this.available = 1;
  }

  acquire() {
    var _this = this;

    return _asyncToGenerator(function* () {
      if (_this.available > 0) {
        _this.available -= 1;
        return Promise.resolve(true);
      }

      // If there is no permit available, we return a promise that resolves once the semaphore gets
      // signaled enough times that "available" is equal to one.
      return new Promise(function (resolver) {
        return _this.queue.push(resolver);
      });
    })();
  }

  release() {
    this.available += 1;

    if (this.available > 1 && this.queue.length > 0) {
      throw new Error('this.available should never be > 0 when there is someone waiting.');
    } else if (this.available === 1 && this.queue.length > 0) {
      // If there is someone else waiting, immediately consume the permit that was released
      // at the beginning of this function and let the waiting function resume.
      this.available -= 1;

      const nextResolver = this.queue.shift();
      if (nextResolver) {
        nextResolver(true);
      }
    }
  }
}
exports.Semaphore = Semaphore;
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