atriusmaps-node-sdk/dist/cjs/plugins/wayfinder/src/minPriorityQueue.js

This project provides an API to Atrius Personal Wayfinder maps within a Node environment. See the README.md for more information

'use strict';

class MinPriorityQueue {
  constructor () {
    this.heap = [null]; // array representation of binary heap
    this.heapMap = {};
  }

  offerWithPriority (node, priority) {
    const index = this.heap.push([node, priority]) - 1;

    this.heapMap[node] = index;
    this.bubble(index);
  }

  raisePriority (node, priority) {
    const index = this.heapMap[node];
    this.heap[index][1] = priority;

    this.bubble(index);
  }

  poll () {
    if (this.heap.length === 1) {
      return null
    }
    if (this.heap.length === 2) {
      const value = this.heap.pop()[0];
      delete this.heapMap[value];
      return value
    }

    const value = this.heap[1][0];
    delete this.heapMap[value];

    this.heap[1] = this.heap.pop();
    this.heapMap[this.heap[1][0]] = 1;

    this.sink(1);

    return value
  }

  isEmpty () {
    return this.heap.length === 1
  }

  bubble (i) {
    while (i > 1) {
      const parentIndex = i >> 1; // floor(i/2)

      if (!this.isHigherPriority(i, parentIndex)) {
        break
      }

      this.swap(i, parentIndex);
      i = parentIndex;
    }
  }

  sink (i) {
    while (i * 2 < this.heap.length) {
      const isRightChildHigherPriority = (this.heap[i * 2 + 1] === undefined)
        ? false
        : this.isHigherPriority(i * 2 + 1, i * 2); // i*2 +1 might be null
      const childIndex = isRightChildHigherPriority ? i * 2 + 1 : i * 2;

      if (this.isHigherPriority(i, childIndex)) {
        break
      }

      this.swap(i, childIndex);
      i = childIndex;
    }
  }

  swap (i, j) {
    this.heapMap[this.heap[i][0]] = j;
    this.heapMap[this.heap[j][0]] = i;

    const temp = this.heap[i];
    this.heap[i] = this.heap[j];
    this.heap[j] = temp;
  }

  isHigherPriority (i, j) {
    return this.heap[i][1] < this.heap[j][1] // lower score -> higher priority
  }
}

module.exports = MinPriorityQueue;