expand add annotation when writing on its left edge

app/components/SimpleEditor/elements/track_change/TrackChangesProvider.js

@@ -27,17 +27,35 @@ class TrackChangesProvider {
     if (status !== 'add') return
 
     const isSelectionCollapsed = this.isSelectionCollapsed()
-    const mode = this.getMode()
+    // const mode = this.getMode()
 
     let selection
 
     if (isSelectionCollapsed) {
       this.insertText(event)
-      if (mode) return
-      selection = this.setSelectionPlusOne('left')
-      this.createAddAnnotation(selection)
-      this.moveCursorTo('end')
-      return
+
+      const notOnTrack = this.isNotOnTrackAnnotation()
+
+      if (notOnTrack) {
+        selection = this.setSelectionPlusOne('left')
+        this.createAddAnnotation(selection)
+        this.moveCursorTo('end')
+        return
+      } else {
+        const isOnAdd = this.isOnAnnotation('add')
+
+        if (isOnAdd) {
+          const annotation = this.getAnnotationByStatus('add')
+          const isOnLeftEdge = this.isOnLeftEdge(annotation)
+
+          if (isOnLeftEdge) {
+            selection = this.setSelectionPlusOne('left')
+            this.expandTrackAnnotation(selection, annotation)
+            this.moveCursorTo('end')
+            return
+          }
+        }
+      }
     } else {
       selection = this.getSelection()
       this.createDeleteAnnotation(selection)
@@ -98,8 +116,9 @@ class TrackChangesProvider {
 
   createTrackAnnotation (selection, status) {
     const surface = this.getSurface()
+    const info = this.getInfo()
 
-    surface.transaction((tx, args) => {
+    const transformation = (tx, args) => {
       const newNode = {
         selection: selection,
         node: {
@@ -108,18 +127,23 @@ class TrackChangesProvider {
         }
       }
       createAnnotation(tx, newNode)
-    })
+    }
+
+    surface.transaction(transformation, info)
   }
 
   expandTrackAnnotation (selection, annotation) {
     const surface = this.getSurface()
+    const info = this.getInfo()
 
-    surface.transaction((tx, args) => {
+    const transformation = (tx, args) => {
       args.selection = selection
       args.anno = annotation
 
       expandAnnotation(tx, args)
-    })
+    }
+
+    surface.transaction(transformation, info)
   }
 
   separateAnnotations () {
@@ -177,6 +201,12 @@ class TrackChangesProvider {
     return annotations
   }
 
+  // prevent substance from running getBoundingRectangle,
+  // as we will unset the selection manually
+  getInfo () {
+    return { skipSelection: true }
+  }
+
   // returns whether the selection is on an add / delete tracked change
   isOnAnnotation (status) {
     const annotations = this.getAllExistingTrackAnnotations()
@@ -188,6 +218,16 @@ class TrackChangesProvider {
     return true
   }
 
+  isOnLeftEdge (annotation) {
+    const selection = this.getSelection()
+    return (selection.startOffset === annotation.startOffset)
+  }
+
+  isNotOnTrackAnnotation () {
+    const mode = this.getMode()
+    return (mode === null)
+  }
+
   /**
 
     HISTORY HANDLERS