Changeset: Move changeset logic to a new Changeset class

Author: rhansen

src/node/handler/PadMessageHandler.js

@@ -582,11 +582,10 @@ const handleUserChanges = async (socket, message) => {
     const wireApool = (new AttributePool()).fromJsonable(apool);
     const pad = await padManager.getPad(thisSession.padId);
 
-    // Verify that the changeset has valid syntax and is in canonical form
-    Changeset.checkRep(changeset);
+    const cs = Changeset.unpack(changeset).validate();
 
     // Validate all added 'author' attribs to be the same value as the current user
-    for (const op of Changeset.deserializeOps(Changeset.unpack(changeset).ops)) {
+    for (const op of Changeset.deserializeOps(cs.ops)) {
       // + can add text with attribs
       // = can change or add attribs
       // - can have attribs, but they are discarded and don't show up in the attribs -

src/node/utils/padDiff.js

@@ -438,7 +438,7 @@ PadDiff.prototype._createDeletionChangeset = function (cs, startAText, apool) {
     }
   }
 
-  return Changeset.checkRep(builder.toString());
+  return builder.build().validate().toString();
 };
 
 // export the constructor