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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+module.metadata = {
+ "stability": "experimental"
+};
+
+exports.Collection = Collection;
+
+/**
+ * Adds a collection property to the given object. Setting the property to a
+ * scalar value empties the collection and adds the value. Setting it to an
+ * array empties the collection and adds all the items in the array.
+ *
+ * @param obj
+ * The property will be defined on this object.
+ * @param propName
+ * The name of the property.
+ * @param array
+ * If given, this will be used as the collection's backing array.
+ */
+exports.addCollectionProperty = function addCollProperty(obj, propName, array) {
+ array = array || [];
+ let publicIface = new Collection(array);
+
+ Object.defineProperty(obj, propName, {
+ configurable: true,
+ enumerable: true,
+
+ set: function set(itemOrItems) {
+ array.splice(0, array.length);
+ publicIface.add(itemOrItems);
+ },
+
+ get: function get() {
+ return publicIface;
+ }
+ });
+};
+
+/**
+ * A collection is ordered, like an array, but its items are unique, like a set.
+ *
+ * @param array
+ * The collection is backed by an array. If this is given, it will be
+ * used as the backing array. This way the caller can fully control the
+ * collection. Otherwise a new empty array will be used, and no one but
+ * the collection will have access to it.
+ */
+function Collection(array) {
+ array = array || [];
+
+ /**
+ * Provides iteration over the collection. Items are yielded in the order
+ * they were added.
+ */
+ this.__iterator__ = function Collection___iterator__() {
+ let items = array.slice();
+ for (let i = 0; i < items.length; i++)
+ yield items[i];
+ };
+
+ /**
+ * The number of items in the collection.
+ */
+ this.__defineGetter__("length", function Collection_get_length() {
+ return array.length;
+ });
+
+ /**
+ * Adds a single item or an array of items to the collection. Any items
+ * already contained in the collection are ignored.
+ *
+ * @param itemOrItems
+ * An item or array of items.
+ * @return The collection.
+ */
+ this.add = function Collection_add(itemOrItems) {
+ let items = toArray(itemOrItems);
+ for (let i = 0; i < items.length; i++) {
+ let item = items[i];
+ if (array.indexOf(item) < 0)
+ array.push(item);
+ }
+ return this;
+ };
+
+ /**
+ * Removes a single item or an array of items from the collection. Any items
+ * not contained in the collection are ignored.
+ *
+ * @param itemOrItems
+ * An item or array of items.
+ * @return The collection.
+ */
+ this.remove = function Collection_remove(itemOrItems) {
+ let items = toArray(itemOrItems);
+ for (let i = 0; i < items.length; i++) {
+ let idx = array.indexOf(items[i]);
+ if (idx >= 0)
+ array.splice(idx, 1);
+ }
+ return this;
+ };
+};
+
+function toArray(itemOrItems) {
+ let isArr = itemOrItems &&
+ itemOrItems.constructor &&
+ itemOrItems.constructor.name === "Array";
+ return isArr ? itemOrItems : [itemOrItems];
+}