basant307/AI_Governance_Project

1module.exports = Pend;2 3function Pend() {4  this.pending = 0;5  this.max = Infinity;6  this.listeners = [];7  this.waiting = [];8  this.error = null;9}10 11Pend.prototype.go = function(fn) {12  if (this.pending < this.max) {13    pendGo(this, fn);14  } else {15    this.waiting.push(fn);16  }17};18 19Pend.prototype.wait = function(cb) {20  if (this.pending === 0) {21    cb(this.error);22  } else {23    this.listeners.push(cb);24  }25};26 27Pend.prototype.hold = function() {28  return pendHold(this);29};30 31function pendHold(self) {32  self.pending += 1;33  var called = false;34  return onCb;35  function onCb(err) {36    if (called) throw new Error("callback called twice");37    called = true;38    self.error = self.error || err;39    self.pending -= 1;40    if (self.waiting.length > 0 && self.pending < self.max) {41      pendGo(self, self.waiting.shift());42    } else if (self.pending === 0) {43      var listeners = self.listeners;44      self.listeners = [];45      listeners.forEach(cbListener);46    }47  }48  function cbListener(listener) {49    listener(self.error);50  }51}52 53function pendGo(self, fn) {54  fn(pendHold(self));55}56