fury-js/src/indexedMap.js

WebGL Game Engine

module.exports = (function(){
	// This creates a dictionary that provides its own keys
	// It also contains an array of keys for quick enumeration
	// This does of course slow removal, so this structure should
	// be used for arrays where you want to enumerate a lot and 
	// also want references that do not go out of date when 
	// you remove an item (which is hopefully rarely).

	// Can this be replaced with Map?
	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
	// An issue is the lack of a sort functionw without creating a new map, which is used 
	// when adding new objects to sceneObjects (in scene.add in the scene module) to group objects
	// by their material.

	// Please note, again for purposes of speed and ease of use 
	// this structure adds the key of the item to the id property on items added
	// this eases checking for duplicates and if you have the only reference
	// you can still remove it from the list or check if it is in the list. 
	let exports = {};
	let nextKey = 1;
	// Not entirely sure why we're reusing keys across all indexed maps 
	// but I don't think it does any harm :shrug:

	let prototype = {
		add: function(item, sortFunction) {
			if (!item.id || !this[item.id]) {
				let key = (nextKey++).toString();
				item.id = key;
				this[key] = item;
				this.keys.push(key);
				if (sortFunction) {
					this.keys.sort(sortFunction);
				}
			}
			return item.id;
		},
		sort: function(sortFunction) {
			if (sortFunction) {
				this.keys.sort(sortFunction);
			} else {
				this.keys.sort();
			}
		},
		remove: function(key) {
			if(key != "keys" && this.hasOwnProperty(key)) {
				this[key].id = null;
				if(delete this[key]) {
					for(let i = 0, l = this.keys.length; i < l; i++) {
						if(this.keys[i] == key) {
							this.keys.splice(i,1);
						}
					}
					return true;
				}
			}
			return false;
		},
		clear: function() {
			for(var i = 0, l = this.keys.length; i < l; i++) {
				delete this[this.keys[i]];
			}
			this.keys.length = 0;
		}
	};

	exports.create = function() {
		// TODO: Option to specify property name to use for id, defaulting to "id"
		let map = Object.create(prototype);
		map.keys = [];
		return map;
	};

	return exports;
})();