@javelin/net/dist/esm/heap.js

Networking protocol and utilities for Javelin ECS.

import { Comparator } from "./comparator";
export class Heap {
    constructor(comparatorFunction) {
        if (new.target === Heap) {
            throw new TypeError("Cannot construct Heap instance directly");
        }
        // Array representation of the heap.
        this.heapContainer = [];
        this.compare = new Comparator(comparatorFunction);
    }
    getLeftChildIndex(parentIndex) {
        return 2 * parentIndex + 1;
    }
    getRightChildIndex(parentIndex) {
        return 2 * parentIndex + 2;
    }
    getParentIndex(childIndex) {
        return Math.floor((childIndex - 1) / 2);
    }
    hasParent(childIndex) {
        return this.getParentIndex(childIndex) >= 0;
    }
    hasLeftChild(parentIndex) {
        return this.getLeftChildIndex(parentIndex) < this.heapContainer.length;
    }
    hasRightChild(parentIndex) {
        return this.getRightChildIndex(parentIndex) < this.heapContainer.length;
    }
    leftChild(parentIndex) {
        return this.heapContainer[this.getLeftChildIndex(parentIndex)];
    }
    rightChild(parentIndex) {
        return this.heapContainer[this.getRightChildIndex(parentIndex)];
    }
    parent(childIndex) {
        return this.heapContainer[this.getParentIndex(childIndex)];
    }
    swap(indexOne, indexTwo) {
        const tmp = this.heapContainer[indexTwo];
        this.heapContainer[indexTwo] = this.heapContainer[indexOne];
        this.heapContainer[indexOne] = tmp;
    }
    peek() {
        if (this.heapContainer.length === 0) {
            return null;
        }
        return this.heapContainer[0];
    }
    poll() {
        if (this.heapContainer.length === 0) {
            return null;
        }
        if (this.heapContainer.length === 1) {
            return this.heapContainer.pop();
        }
        const item = this.heapContainer[0];
        // Move the last element from the end to the head.
        this.heapContainer[0] = this.heapContainer.pop();
        this.heapifyDown();
        return item;
    }
    add(item) {
        this.heapContainer.push(item);
        this.heapifyUp();
        return this;
    }
    remove(item, comparator = this.compare) {
        const numberOfItemsToRemove = this.find(item, comparator).length;
        for (let iteration = 0; iteration < numberOfItemsToRemove; iteration += 1) {
            const indexToRemove = this.find(item, comparator).pop();
            if (indexToRemove === this.heapContainer.length - 1) {
                this.heapContainer.pop();
            }
            else {
                this.heapContainer[indexToRemove] = this.heapContainer.pop();
                const parentItem = this.parent(indexToRemove);
                if (this.hasLeftChild(indexToRemove) &&
                    (!parentItem ||
                        this.pairIsInCorrectOrder(parentItem, this.heapContainer[indexToRemove]))) {
                    this.heapifyDown(indexToRemove);
                }
                else {
                    this.heapifyUp(indexToRemove);
                }
            }
        }
        return this;
    }
    find(item, comparator = this.compare) {
        const foundItemIndices = [];
        for (let itemIndex = 0; itemIndex < this.heapContainer.length; itemIndex += 1) {
            if (comparator.equal(item, this.heapContainer[itemIndex])) {
                foundItemIndices.push(itemIndex);
            }
        }
        return foundItemIndices;
    }
    isEmpty() {
        return !this.heapContainer.length;
    }
    toString() {
        return this.heapContainer.toString();
    }
    heapifyUp(startIndex = this.heapContainer.length - 1) {
        while (this.hasParent(startIndex) &&
            !this.pairIsInCorrectOrder(this.parent(startIndex), this.heapContainer[startIndex])) {
            this.swap(startIndex, this.getParentIndex(startIndex));
            startIndex = this.getParentIndex(startIndex);
        }
    }
    heapifyDown(customStartIndex = 0) {
        let currentIndex = customStartIndex;
        let nextIndex = null;
        while (this.hasLeftChild(currentIndex)) {
            if (this.hasRightChild(currentIndex) &&
                this.pairIsInCorrectOrder(this.rightChild(currentIndex), this.leftChild(currentIndex))) {
                nextIndex = this.getRightChildIndex(currentIndex);
            }
            else {
                nextIndex = this.getLeftChildIndex(currentIndex);
            }
            if (this.pairIsInCorrectOrder(this.heapContainer[currentIndex], this.heapContainer[nextIndex])) {
                break;
            }
            this.swap(currentIndex, nextIndex);
            currentIndex = nextIndex;
        }
    }
    pairIsInCorrectOrder(firstElement, secondElement) {
        throw new Error(`
      You have to implement heap pair comparision method
      for ${firstElement} and ${secondElement} values.
    `);
    }
}
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