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Viewing / Editing File: PriorityQueue.js

'use strict';

Object.defineProperty(exports, '__esModule', {
  value: true
});
exports.default = void 0;

/**
 * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

/**
 * Priority queue that processes tasks in natural ordering (lower priority first)
 * accoridng to the priority computed by the function passed in the constructor.
 *
 * FIFO ordering isn't guaranteed for tasks with the same priority.
 *
 * Worker specific tasks with the same priority as a non-worker specific task
 * are always processed first.
 */
class PriorityQueue {
  constructor(_computePriority) {
    this._computePriority = _computePriority;

_defineProperty(this, '_queue', []);

_defineProperty(this, '_sharedQueue', new MinHeap());
  }

enqueue(task, workerId) {
    if (workerId == null) {
      this._enqueue(task, this._sharedQueue);
    } else {
      const queue = this._getWorkerQueue(workerId);

this._enqueue(task, queue);
    }
  }

_enqueue(task, queue) {
    const item = {
      priority: this._computePriority(task.request[2], ...task.request[3]),
      task
    };
    queue.add(item);
  }

dequeue(workerId) {
    const workerQueue = this._getWorkerQueue(workerId);

const workerTop = workerQueue.peek();

const sharedTop = this._sharedQueue.peek(); // use the task from the worker queue if there's no task in the shared queue
    // or if the priority of the worker queue is smaller or equal to the
    // priority of the top task in the shared queue. The tasks of the
    // worker specific queue are preferred because no other worker can pick this
    // specific task up.

if (
      sharedTop == null ||
      (workerTop != null && workerTop.priority <= sharedTop.priority)
    ) {
      var _workerQueue$poll$tas, _workerQueue$poll;

return (_workerQueue$poll$tas =
        (_workerQueue$poll = workerQueue.poll()) === null ||
        _workerQueue$poll === void 0
          ? void 0
          : _workerQueue$poll.task) !== null && _workerQueue$poll$tas !== void 0
        ? _workerQueue$poll$tas
        : null;
    }

return this._sharedQueue.poll().task;
  }

_getWorkerQueue(workerId) {
    let queue = this._queue[workerId];

if (queue == null) {
      queue = this._queue[workerId] = new MinHeap();
    }

return queue;
  }
}

exports.default = PriorityQueue;

class MinHeap {
  constructor() {
    _defineProperty(this, '_heap', []);
  }

peek() {
    var _this$_heap$;

return (_this$_heap$ = this._heap[0]) !== null && _this$_heap$ !== void 0
      ? _this$_heap$
      : null;
  }

add(item) {
    const nodes = this._heap;
    nodes.push(item);

if (nodes.length === 1) {
      return;
    }

let currentIndex = nodes.length - 1; // Bubble up the added node as long as the parent is bigger

while (currentIndex > 0) {
      const parentIndex = Math.floor((currentIndex + 1) / 2) - 1;
      const parent = nodes[parentIndex];

if (parent.priority <= item.priority) {
        break;
      }

nodes[currentIndex] = parent;
      nodes[parentIndex] = item;
      currentIndex = parentIndex;
    }
  }

poll() {
    const nodes = this._heap;
    const result = nodes[0];
    const lastElement = nodes.pop(); // heap was empty or removed the last element

if (result == null || nodes.length === 0) {
      return result !== null && result !== void 0 ? result : null;
    }

let index = 0;
    nodes[0] =
      lastElement !== null && lastElement !== void 0 ? lastElement : null;
    const element = nodes[0];

while (true) {
      let swapIndex = null;
      const rightChildIndex = (index + 1) * 2;
      const leftChildIndex = rightChildIndex - 1;
      const rightChild = nodes[rightChildIndex];
      const leftChild = nodes[leftChildIndex]; // if the left child is smaller, swap with the left

if (leftChild != null && leftChild.priority < element.priority) {
        swapIndex = leftChildIndex;
      } // If the right child is smaller or the right child is smaller than the left
      // then swap with the right child

if (
        rightChild != null &&
        rightChild.priority < (swapIndex == null ? element : leftChild).priority
      ) {
        swapIndex = rightChildIndex;
      }

if (swapIndex == null) {
        break;
      }

nodes[index] = nodes[swapIndex];
      nodes[swapIndex] = element;
      index = swapIndex;
    }

return result;
  }
}

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