/**
 * Priority lists allow you to create an indexed list that can be iterated through in a specific
 * order.
 */
elgg.ElggPriorityList = function() {
	this.length = 0;
	this.priorities_ = [];
};

/**
 * Inserts an element into the priority list at the priority specified.
 *
 * @param {Object} obj          The object to insert
 * @param {Number} opt_priority An optional priority to insert at.
 * 
 * @return {Void}
 */
elgg.ElggPriorityList.prototype.insert = function(obj, opt_priority) {
	var priority = 500;
	if (arguments.length == 2 && opt_priority != undefined) {
		priority = parseInt(opt_priority, 10);
	}

	priority = Math.max(priority, 0);

	if (elgg.isUndefined(this.priorities_[priority])) {
		this.priorities_[priority] = [];
	}

	this.priorities_[priority].push(obj);
	this.length++;
};

/**
 * Iterates through each element in order.
 *
 * Unlike every, this ignores the return value of the callback.
 *
 * @param {Function} callback The callback function to pass each element through. See
 *                            Array.prototype.every() for details.
 * @return {Object}
 */
elgg.ElggPriorityList.prototype.forEach = function(callback) {
	elgg.assertTypeOf('function', callback);

	var index = 0;

	this.priorities_.forEach(function(elems) {
		elems.forEach(function(elem) {
			callback(elem, index++);
		});
	});

	return this;
};

/**
 * Iterates through each element in order.
 *
 * Unlike forEach, this returns the value of the callback and will break on false.
 *
 * @param {Function} callback The callback function to pass each element through. See
 *                            Array.prototype.every() for details.
 * @return {Object}
 */
elgg.ElggPriorityList.prototype.every = function(callback) {
	elgg.assertTypeOf('function', callback);

	var index = 0;

	return this.priorities_.every(function(elems) {
		return elems.every(function(elem) {
			return callback(elem, index++);
		});
	});
};

/**
 * Removes an element from the priority list
 *
 * @param {Object} obj The object to remove.
 * @return {Void}
 */
elgg.ElggPriorityList.prototype.remove = function(obj) {
	this.priorities_.forEach(function(elems) {
		var index;
		while ((index = elems.indexOf(obj)) !== -1) {
			elems.splice(index, 1);
			this.length--;
		}
	});
};