Move history service to linked list with random UUID

Signed-off-by:Guillaume Martigny <guillaume.martigny@gmail.com>

src/js/service/HistoryService.js

@@ -7,7 +7,7 @@
     this.deserializer = deserializer || pskl.utils.serialization.Deserializer;
 
     this.stateQueue = [];
-    this.currentIndex = -1;
+    this.currentUUID = false;
     this.lastLoadState = -1;
   };
 
@@ -40,42 +40,84 @@
   };
 
   ns.HistoryService.prototype.saveState = function (action) {
-    this.stateQueue = this.stateQueue.slice(0, this.currentIndex + 1);
-    this.currentIndex = this.currentIndex + 1;
-
     var state = {
       action : action,
       frameIndex : action.state ? action.state.frameIndex : this.piskelController.currentFrameIndex,
-      layerIndex : action.state ? action.state.layerIndex : this.piskelController.currentLayerIndex
+      layerIndex : action.state ? action.state.layerIndex : this.piskelController.currentLayerIndex,
+      previousIndex: false,
+      nextIndex: false
     };
 
     var isSnapshot = action.type === ns.HistoryService.SNAPSHOT;
-    var isAtAutoSnapshotInterval = this.currentIndex % ns.HistoryService.SNAPSHOT_PERIOD === 0;
+    var isAtAutoSnapshotInterval = (this.stateQueue.length - 1) % ns.HistoryService.SNAPSHOT_PERIOD === 0;
     if (isSnapshot || isAtAutoSnapshotInterval) {
       state.piskel = this.piskelController.serialize(true);
     }
 
-    this.stateQueue.push(state);
+    this.pushNewState_(state);
     $.publish(Events.HISTORY_STATE_SAVED);
   };
 
+  ns.HistoryService.prototype.getCurrentState = function(){
+    if(this.currentUUID){
+      return this.stateQueue[this.currentUUID];
+    }
+    else{
+      return false;
+    }
+  };
+
+  ns.HistoryService.prototype.pushNewState_ = function(state){
+    // Generate a random UUID (~1e28 combinations)
+    var uuid = 'xxxxxx'.replace(/x/g, function(){
+      return (Math.random() * 36 << 0).toString(36);
+    });
+
+    var currentState = this.getCurrentState();
+    if(currentState){
+      // Clear unlinked states
+      if(currentState.nextIndex){
+        this.clearBranchingQueue_(currentState.nextIndex);
+      }
+
+      currentState.nextIndex = uuid;
+    }
+
+    state.previousIndex = this.currentUUID;
+    this.stateQueue[uuid] = state;
+
+    this.currentUUID = uuid;
+  };
+
+  ns.HistoryService.prototype.clearBranchingQueue_ = function(index){
+    while(this.stateQueue[index]){
+      var next = this.stateQueue[index].nextIndex;
+      delete(this.stateQueue[index]);
+      index = next;
+    }
+  };
+
   ns.HistoryService.prototype.undo = function () {
-    this.loadState(this.currentIndex - 1);
+    var currentState = this.getCurrentState();
+    if(currentState.previousIndex)
+      this.loadState(currentState.previousIndex);
   };
 
   ns.HistoryService.prototype.redo = function () {
-    this.loadState(this.currentIndex + 1);
+    var currentState = this.getCurrentState();
+    if(currentState.nextIndex)
+      this.loadState(currentState.nextIndex);
   };
 
   ns.HistoryService.prototype.isLoadStateAllowed_ = function (index) {
     var timeOk = (Date.now() - this.lastLoadState) > ns.HistoryService.LOAD_STATE_INTERVAL;
-    var indexInRange = index >= 0 && index < this.stateQueue.length;
+    var indexInRange = index && this.stateQueue[index];
     return timeOk && indexInRange;
   };
 
   ns.HistoryService.prototype.getPreviousSnapshotIndex_ = function (index) {
     while (this.stateQueue[index] && !this.stateQueue[index].piskel) {
-      index = index - 1;
+      index = this.stateQueue[index].previousIndex;
     }
     return index;
   };
@@ -86,7 +128,7 @@
         this.lastLoadState = Date.now();
 
         var snapshotIndex = this.getPreviousSnapshotIndex_(index);
-        if (snapshotIndex < 0) {
+        if (!snapshotIndex) {
           throw 'Could not find previous SNAPSHOT saved in history stateQueue';
         }
         var serializedPiskel = this.getSnapshotFromState_(snapshotIndex);
@@ -97,7 +139,7 @@
       console.error('[CRITICAL ERROR] : Unable to load a history state.');
       this.logError_(error);
       this.stateQueue = [];
-      this.currentIndex = -1;
+      this.currentUUID = false;
     }
   };
 
@@ -132,19 +174,21 @@
     piskel.savePath = this.piskelController.piskel.savePath;
     this.piskelController.setPiskel(piskel);
 
-    for (var i = snapshotIndex + 1 ; i <= index ; i++) {
+    var walkingIndex = snapshotIndex;
-      var state = this.stateQueue[i];
+    do{
+      walkingIndex = this.stateQueue[walkingIndex].nextIndex;
+      var state = this.stateQueue[walkingIndex];
       this.setupState(state);
       this.replayState(state);
-    }
+    } while(walkingIndex && walkingIndex != index);
 
     // Should only do this when going backwards
-    var lastState = this.stateQueue[index + 1];
+    var next = this.stateQueue[index].nextIndex;
-    if (lastState) {
+    if (next) {
-      this.setupState(lastState);
+      this.setupState(this.stateQueue[next]);
     }
 
-    this.currentIndex = index;
+    this.currentUUID = index;
     $.publish(Events.PISKEL_RESET);
     $.publish(Events.HISTORY_STATE_LOADED);
     if (originalSize !== this.getPiskelSize_()) {