phaser/src/physics/matter-js/lib/collision/Pairs.js

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/**
* The `Matter.Pairs` module contains methods for creating and manipulating collision pair sets.
*
* @class Pairs
*/

var Pairs = {};

module.exports = Pairs;

var Pair = require('./Pair');
var Common = require('../core/Common');

(function() {

    /**
     * Creates a new pairs structure.
     * @method create
     * @param {object} options
     * @return {pairs} A new pairs structure
     */
    Pairs.create = function(options) {
        return Common.extend({ 
            table: {},
            list: [],
            collisionStart: [],
            collisionActive: [],
            collisionEnd: []
        }, options);
    };

    /**
     * Updates pairs given a list of collisions.
     * @method update
     * @param {object} pairs
     * @param {collision[]} collisions
     * @param {number} timestamp
     */
    Pairs.update = function(pairs, collisions, timestamp) {
        var pairsList = pairs.list,
            pairsListLength = pairsList.length,
            pairsTable = pairs.table,
            collisionsLength = collisions.length,
            collisionStart = pairs.collisionStart,
            collisionEnd = pairs.collisionEnd,
            collisionActive = pairs.collisionActive,
            collision,
            pairIndex,
            pair,
            i;

        // clear collision state arrays, but maintain old reference
        collisionStart.length = 0;
        collisionEnd.length = 0;
        collisionActive.length = 0;

        for (i = 0; i < pairsListLength; i++) {
            pairsList[i].confirmedActive = false;
        }

        for (i = 0; i < collisionsLength; i++) {
            collision = collisions[i];
            pair = collision.pair;

            if (pair) {
                // pair already exists (but may or may not be active)
                if (pair.isActive) {
                    // pair exists and is active
                    collisionActive.push(pair);
                } else {
                    // pair exists but was inactive, so a collision has just started again
                    collisionStart.push(pair);
                }

                // update the pair
                Pair.update(pair, collision, timestamp);
                pair.confirmedActive = true;
            } else {
                // pair did not exist, create a new pair
                pair = Pair.create(collision, timestamp);
                pairsTable[pair.id] = pair;

                // push the new pair
                collisionStart.push(pair);
                pairsList.push(pair);
            }
        }

        // find pairs that are no longer active
        var removePairIndex = [];
        pairsListLength = pairsList.length;

        for (i = 0; i < pairsListLength; i++) {
            pair = pairsList[i];
            
            if (!pair.confirmedActive) {
                Pair.setActive(pair, false, timestamp);
                collisionEnd.push(pair);

                if (!pair.collision.bodyA.isSleeping && !pair.collision.bodyB.isSleeping) {
                    removePairIndex.push(i);
                }
            }
        }

        // remove inactive pairs
        for (i = 0; i < removePairIndex.length; i++) {
            pairIndex = removePairIndex[i] - i;
            pair = pairsList[pairIndex];
            pairsList.splice(pairIndex, 1);
            delete pairsTable[pair.id];
        }
    };

    /**
     * Clears the given pairs structure.
     * @method clear
     * @param {pairs} pairs
     * @return {pairs} pairs
     */
    Pairs.clear = function(pairs) {
        pairs.table = {};
        pairs.list.length = 0;
        pairs.collisionStart.length = 0;
        pairs.collisionActive.length = 0;
        pairs.collisionEnd.length = 0;
        return pairs;
    };

})();