[Edit] Add Selection class

Add class to handle selection, which will be synchronized
to the toolbar. WTD-929.

platform/commonUI/edit/src/representers/EditToolbarSelection.js

@@ -0,0 +1,124 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Tracks selection state for Layout and Fixed Position views.
+         * This manages and mutates the provided selection array in-place,
+         * and takes care to only modify the array elements it manages
+         * (the view's proxy, and the single selection); selections may be
+         * added or removed elsewhere provided that similar care is taken
+         * elsewhere.
+         *
+         * @param {Array} selection the selection array from the view's scope
+         * @param [proxy] an object which represents the selection of the view
+         *        itself (which handles view-level toolbar behavior)
+         */
+        function EditToolbarSelection() {
+            var selection = [ {} ],
+                selecting = false,
+                selected;
+
+            // Remove the currently-selected object
+            function deselect() {
+                // Nothing to do if we don't have a selected object
+                if (selecting) {
+                    // Clear state tracking
+                    selecting = false;
+                    selected = undefined;
+
+                    // Remove the selection
+                    selection.pop();
+
+                    return true;
+                }
+                return false;
+            }
+
+            // Select an object
+            function select(obj) {
+                // Proxy is always selected
+                if (obj === selection[0]) {
+                    return false;
+                }
+
+                // Clear any existing selection
+                deselect();
+
+                // Note the current selection state
+                selected = obj;
+                selecting = true;
+
+                // Add the selection
+                selection.push(obj);
+            }
+
+
+            // Check if an object is selected
+            function isSelected(obj) {
+                return (obj === selected) || (obj === selection[0]);
+            }
+
+            // Getter for current selection
+            function get() {
+                return selected;
+            }
+
+            // Getter/setter for view proxy
+            function proxy(p) {
+                if (arguments.length > 0) {
+                    selection[0] = p;
+                }
+                return selection[0];
+            }
+
+            // Getter for the full array of selected objects (incl. view proxy)
+            function all() {
+                return selection;
+            }
+
+            return {
+                /**
+                 * Check if an object is currently selected.
+                 * @returns true if selected, otherwise false
+                 */
+                selected: isSelected,
+                /**
+                 * Select an object.
+                 * @param obj the object to select
+                 * @returns {boolean} true if selection changed
+                 */
+                select: select,
+                /**
+                 * Clear the current selection.
+                 * @returns {boolean} true if selection changed
+                 */
+                deselect: deselect,
+                /**
+                 * Get the currently-selected object.
+                 * @returns the currently selected object
+                 */
+                get: get,
+                /**
+                 * Get/set the view proxy (for toolbar actions taken upon
+                 * the view itself.)
+                 * @param [proxy] the view proxy (if setting)
+                 * @returns the current view proxy
+                 */
+                proxy: proxy,
+                /**
+                 * Get an array containing all selections, including the
+                 * selection proxy. It is generally not advisable to
+                 * mutate this array directly.
+                 * @returns {Array} all selections
+                 */
+                all: all
+            };
+        }
+
+        return EditToolbarSelection;
+    }
+);