function Generator() {}

Generator.prototype.rand = Math.floor(Math.random() * 26) + Date.now();

Generator.prototype.getId = function () {
  return this.rand++;
};

function Queue() {
  this.elements = [];
  this.forceStop = false;
  this.state = "INITIALIZED";
  this.idGen = new Generator();
}
// add a request to the queue
Queue.prototype.enqueue = function (request, data) {
  var id = this.idGen.getId();
  var queue_data = {
    id: id,
    data: data,
    state: "INQUEUE", // PROCESSING, SUCCEED, FAILED
    request: request,
    response: "",
  };
  this.elements.push(queue_data);
  return id;
};

// Queue.prototype.dequeue = function () {
//   return this.elements.shift();
// };

//clear the queue
Queue.prototype.clear = function () {
  this.elements = [];
  this.state = "INITIALIZED";
};
// check if queue items is emtry
Queue.prototype.isEmpty = function () {
  return this.elements.length == 0;
};
// get the queue item that failed
Queue.prototype.getById = function (id) {
  if (!this.isEmpty()) {
    var res = $.grep(this.elements, function (data) {
      return data.id == id;
    });
    if (res.length > 0) return res[0];
  }
  return undefined;
};
// get the current queue item that is processing
Queue.prototype.getCurrentProcessing = function (id) {
  if (!this.isEmpty()) {
    var res = $.grep(this.elements, function (data) {
      return data.state == "PROCESSING";
    });
    if (res.length > 0) return res[res.length - 1];
  }
  return undefined;
};
// get the queue item that failed
Queue.prototype.getFail = function (id) {
  if (!this.isEmpty()) {
    var res = $.grep(this.elements, function (data) {
      return data.state == "FAILED";
    });
    if (res.length > 0) return res[0];
  }
  return undefined;
};
// get the total number of queue items
Queue.prototype.length = function () {
  return this.elements.length;
};

//terminate queue
Queue.prototype.stop = function () {
  this.state = "STOPPED";
  this.forceStop = true;
};

//start the queue
Queue.prototype.start = async function (callback, fromFail = false) {
  let $this = this;
  $this.forceStop = false;
  $this.state = "PROCESSING";
  $this.elements = $.map($this.elements, function (v, i) {
    if (fromFail) {
      if (v.state != "SUCCEED") {
        v.state = "INQUEUE";
      }
    } else {
      v.state = "INQUEUE";
    }
    return v;
  });
  var terminateQueue = false;
  var success = false;
  debugger;
  for (let i = 0; i < $this.length(); i++) {
    if (terminateQueue) break;
    if ($this.forceStop) {
      $this.elements[i].state = "TERMINATED";
      return;
    }
    if ($this.elements[i].state == "INQUEUE") {
      $this.elements[i].state = "PROCESSING";

      let promise = new Promise(function (onSuccess, onFailed) {
        getFromAPI(
          $this.elements[i].data,
          function (data) {
            // set queue element response
            $this.elements[i].response = data;
            if (data.status == false) {
              success = false;
              $this.elements[i].state = "FAILED";
              terminateQueue = true;
            } else if (JSON.stringify(data).indexOf("FAIL") !== -1) {
              success = false;
              $this.elements[i].state = "FAILED";
              terminateQueue = true;
            } else {
              success = true;
              $this.elements[i].state = "SUCCEED";
            }
            onSuccess();
          },
          function () {
            success = false;
            $this.elements[i].response = "HTTP Request failed";
            $this.elements[i].state = "FAILED";
            terminateQueue = true;
            onFailed();
          }
        );
      });
      await promise;
    }
  }

  $this.state = success ? "COMPLETED" : "FAILED";
  if (success) callback(true);
  else callback(false);
};