chat: Move message copy to `padCopy` hook

src/ep.json

@@ -26,6 +26,7 @@
         "eejsBlock_stickyContainer": "ep_etherpad-lite/node/chat",
         "handleMessage": "ep_etherpad-lite/node/chat",
         "padCheck": "ep_etherpad-lite/node/chat",
+        "padCopy": "ep_etherpad-lite/node/chat",
         "padLoad": "ep_etherpad-lite/node/chat",
         "socketio": "ep_etherpad-lite/node/chat"
       }

src/node/chat.js

@@ -156,6 +156,19 @@ exports.padCheck = async (hookName, {pad}) => {
   for (const p of chats.batch(100).buffer(99)) await p;
 };
 
+exports.padCopy = async (hookName, {srcPad, dstPad}) => {
+  const {chatHead = -1} = srcPad;
+  dstPad.chatHead = chatHead;
+  const copyChat = async (i) => {
+    const val = await srcPad.db.get(`pad:${srcPad.id}:chat:${i}`);
+    await dstPad.db.set(`pad:${dstPad.id}:chat:${i}`, val);
+  };
+  const ops = (function* () {
+    for (let i = 0; i <= chatHead; ++i) yield copyChat(i);
+  })();
+  for (const op of new Stream(ops).batch(100).buffer(99)) await op;
+};
+
 exports.padLoad = async (hookName, {pad}) => {
   if (!('chatHead' in pad)) pad.chatHead = -1;
 };

src/node/db/Pad.js

@@ -372,7 +372,6 @@ class Pad {
     const promises = (function* () {
       yield copyRecord('');
       yield* Stream.range(0, this.head + 1).map((i) => copyRecord(`:revs:${i}`));
-      yield* Stream.range(0, this.chatHead + 1).map((i) => copyRecord(`:chat:${i}`));
       yield this.copyAuthorInfoToDestinationPad(destinationID);
       if (destGroupID) yield db.setSub(`group:${destGroupID}`, ['pads', destinationID], 1);
     }).call(this);