+ },
+ undo: function() {
+ var transformationObject = this.undoStack.pop(),
+ doc = this,
+ transformations, stopAt;
+
+ if(transformationObject) {
+ this._undoInProgress = true;
+
+ if(_.isArray(transformationObject)) {
+ // We will modify this array in a minute so make sure we work on a copy.
+ transformations = transformationObject.slice(0);
+ } else {
+ // Lets normalize single transformation to a transaction containing one transformation.
+ transformations = [transformationObject];
+ }
+
+ if(transformations.length > 1) {
+ // In case of real transactions we don't want to run undo on all of transformations if we don't have to.
+ stopAt = undefined;
+ transformations.some(function(t, idx) {
+ if(!t.undo && t.getChangeRoot().sameNode(doc.root)) {
+ stopAt = idx;
+ return true; //break
+ }
+ });
+ if(stopAt !== undefined) {
+ // We will get away with undoing only this transformations as the one at stopAt reverses the whole document.
+ transformations = transformations.slice(0, stopAt+1);
+ }
+ }
+
+ transformations.reverse();
+ transformations.forEach(function(t) {
+ t.undo();
+ });
+
+ this._undoInProgress = false;
+ this.redoStack.push(transformationObject);
+ }
+ },
+ redo: function() {
+ var transformationObject = this.redoStack.pop(),
+ transformations;
+ if(transformationObject) {
+ this._transformationLevel++;
+ transformations = _.isArray(transformationObject) ? transformationObject : [transformationObject];
+ transformations.forEach(function(t) {
+ t.run({beUndoable: true});
+ });
+ this._transformationLevel--;
+ this.undoStack.push(transformationObject);
+ }
+ },
+
+ startTransaction: function() {
+ if(this._transactionInProgress) {
+ throw new Error('Nested transactions not supported!');
+ }
+ this._transactionInProgress = true;
+ },
+
+ endTransaction: function() {
+ if(!this._transactionInProgress) {
+ throw new Error('End of transaction requested, but there is no transaction in progress!');