Daniel@0: "use strict";
Daniel@0: 
Daniel@0: App.module("ContextModule", function(ContextModule, App, Backbone, Marionette, $, _, Logger) {
Daniel@0: 
Daniel@0:     // Define private variables
Daniel@0:     var logger = null;
Daniel@0: 
Daniel@0:     ContextModule.addInitializer(function(options){
Daniel@0:         
Daniel@0: //        logger = Logger.get("ContextModule.StateBookmark");
Daniel@0: //        logger.setLevel(Logger.DEBUG);
Daniel@0:         
Daniel@0:         /**
Daniel@0:          * StateHistory stores a history of a serialized state
Daniel@0:          * and provides an API to switch between these states
Daniel@0:          * 
Daniel@0:          * A user simply updates the value of currentSerializedState attribute
Daniel@0:          * and calls undo(), redo() or reset() to move along the history
Daniel@0:          * There is no direct access to undo and redo stacks, but it is possible
Daniel@0:          * to know about them by calling canUndo() and canRedo()
Daniel@0:          * 
Daniel@0:          * serialize / unserialize deal with the object of the following structure
Daniel@0:          *      {
Daniel@0:          *          undoStack: [{recent}, {less recent}, ... {the oldest}]
Daniel@0:          *          redoStack: [{next}, {the following}, ... {the last}]
Daniel@0:          *          currentSerializedState: {}
Daniel@0:          *      }
Daniel@0:          *      
Daniel@0:          * attribute compoundChangeDetector is a function that helps decide if the changes between
Daniel@0:          *      the given three serialized states can be treated as a single change.
Daniel@0:          *      This is needed to avoid too many undo states on simple actions like text typing
Daniel@0:          *      compoundChangeDetector returns true if the change between the first, the second
Daniel@0:          *      and the third object can be considered as a single compound change
Daniel@0:          *      (i.e. there is no need to create an extra undo action)
Daniel@0:          */
Daniel@0:         ContextModule.StateHistory = Backbone.Model.extend({
Daniel@0:             defaults: {
Daniel@0:                 maxStackSize: 50,
Daniel@0:                 currentSerializedState: undefined,
Daniel@0:                 compoundChangeDetector: undefined
Daniel@0:             },
Daniel@0: 
Daniel@0:             _NONE: 0,
Daniel@0:             _UNDO: 1,
Daniel@0:             _REDO: 2,
Daniel@0:             _UNSERIALIZE: 3,
Daniel@0:             
Daniel@0:             /**
Daniel@0:              * @memberOf App.ContextModule.StateBookmark
Daniel@0:              */
Daniel@0:             initialize: function() {
Daniel@0:                 this._undoStack = []; 
Daniel@0:                 this._redoStack = [];
Daniel@0:                 this._currentSerializedStateChangeMode = this._NONE;
Daniel@0:                 
Daniel@0:                 this.on("change:maxStackSize", this._trimStacks, this);
Daniel@0:                 this.on("change:currentSerializedState", this._registerNewSerializedState, this);
Daniel@0:             },
Daniel@0: 
Daniel@0:             _registerNewSerializedState: function() {
Daniel@0:                 var previousSerialisedState = this.previous("currentSerializedState");
Daniel@0:                 if (this._currentSerializedStateChangeMode == this._UNDO) {
Daniel@0:                     this._redoStack.unshift(previousSerialisedState);
Daniel@0:                 } else if (this._currentSerializedStateChangeMode == this._REDO) {
Daniel@0:                     this._undoStack.unshift(previousSerialisedState);
Daniel@0:                 } else if (this._currentSerializedStateChangeMode == this._UNSERIALIZE) {
Daniel@0:                 } else {
Daniel@0:                     if (!_.isEqual(previousSerialisedState, this.attributes.currentSerializedState)) {
Daniel@0:                         if (this._undoStack.length == 0
Daniel@0:                             || !_.isFunction(this.attributes.compoundChangeDetector)
Daniel@0:                             || !this.attributes.compoundChangeDetector.call(currentSerializedState, previousSerialisedState, this._undoStack[0]))
Daniel@0:                         {
Daniel@0:                             this._undoStack.unshift(previousSerialisedState);
Daniel@0:                         }
Daniel@0:                         this._redoStack = [];
Daniel@0:                     }
Daniel@0:                 }
Daniel@0:                 this._trimStacks();
Daniel@0:             },
Daniel@0:             
Daniel@0:             getCurrentSerializedState: function() {
Daniel@0:                 
Daniel@0:             },
Daniel@0:             
Daniel@0:             undo: function() {
Daniel@0:                 if (this._undoStack.length) {
Daniel@0:                     this._currentSerializedStateChangeMode = this._UNDO;
Daniel@0:                     this.set("currentSerializedState", this._undoStack.shift());
Daniel@0:                     this._currentSerializedStateChangeMode = this._NONE;
Daniel@0:                 } else {
Daniel@0:                     throw "Undo was called when undo stack was empty";
Daniel@0:                 }
Daniel@0:             },
Daniel@0:             
Daniel@0:             redo: function() {
Daniel@0:                 if (this._redoStack.length) {
Daniel@0:                     this._currentSerializedStateChangeMode = this._REDO;
Daniel@0:                     this.set("currentSerializedState", this._redoStack.shift());
Daniel@0:                     this._currentSerializedStateChangeMode = this._NONE;
Daniel@0:                 } else {
Daniel@0:                     throw "Redo was called when undo stack was empty";
Daniel@0:                 }
Daniel@0:             },
Daniel@0:             
Daniel@0:             reset: function() {
Daniel@0:                 var stacksWereNotEmpty = this._undoStack.length || this._redoStack.length;
Daniel@0:                 this._undoStack = [];
Daniel@0:                 this._redoStack = [];
Daniel@0:                 if (stacksWereNotEmpty) {
Daniel@0:                     this.trigger("change");
Daniel@0:                 }
Daniel@0:             },
Daniel@0:             
Daniel@0:             canUndo: function() {
Daniel@0:                 return !!this._undoStack.length;
Daniel@0:             },
Daniel@0:             
Daniel@0:             canRedo: function() {
Daniel@0:                 return !!this._redoStack.length;
Daniel@0:             },
Daniel@0:             
Daniel@0:             serialize: function() {
Daniel@0: //                logger.debug("method called: StateHistory::serialize");
Daniel@0: 
Daniel@0:                 var result = {
Daniel@0:                         currentSerializedState: this.attributes.currentSerializedState,
Daniel@0:                         undoStack: _.clone(this._undoStack),
Daniel@0:                         redoStack: _.clone(this._redoStack),
Daniel@0:                 };
Daniel@0: 
Daniel@0:                 return result;
Daniel@0:             },
Daniel@0: 
Daniel@0:             unserialize: function(serializedAttributes) {
Daniel@0:                 this._currentSerializedStateChangeMode = this._UNSERIALIZE;
Daniel@0:                 
Daniel@0:                 var fixedSerializedAttributes = serializedAttributes;
Daniel@0:                 if (!_.isSimpleObject(serializedAttributes)) {
Daniel@0:                     fixedSerializedAttributes = {};
Daniel@0:                 }
Daniel@0:                 
Daniel@0:                 this._undoStack = _.isArray(fixedSerializedAttributes.undoStack) ?
Daniel@0:                         fixedSerializedAttributes.undoStack : [];
Daniel@0:                 this._redoStack = _.isArray(fixedSerializedAttributes.redoStack) ?
Daniel@0:                         fixedSerializedAttributes.redoStack : [];
Daniel@0:                 this._trimStacks();
Daniel@0: 
Daniel@0:                 this.set("currentSerializedState", fixedSerializedAttributes.currentSerializedState);
Daniel@0: 
Daniel@0:                 this._currentSerializedStateChangeMode = this._NONE;
Daniel@0:             },
Daniel@0:             
Daniel@0:             _trimStacks: function() {
Daniel@0:                 if (this._undoStack.length > this.attributes.maxStackSize) {
Daniel@0:                     this._undoStack = this._undoStack.slice(0, this.attributes.maxStackSize);
Daniel@0:                 }
Daniel@0:                 if (this._redoStack.length > this.attributes.maxStackSize) {
Daniel@0:                     this._redoStack = this._redoStack.slice(0, this.attributes.maxStackSize);
Daniel@0:                 }
Daniel@0:             }
Daniel@0:         });
Daniel@0: 
Daniel@0:     });
Daniel@0: }, Logger);