From bf05e9ae89a73a1ceead364c42a2f66744c75723 Mon Sep 17 00:00:00 2001
From: anugu-chegg <anugu.s@chegg.com>
Date: Sat, 10 Feb 2018 22:30:22 +0530
Subject: [PATCH] Handle client reconnect properly

---
 src/node/handler/PadMessageHandler.js | 76 +++++++++++++++++++++++++++
 src/static/js/collab_client.js        | 57 ++++++++++++++++++--
 src/static/js/pad.js                  |  4 +-
 3 files changed, 131 insertions(+), 6 deletions(-)

diff --git a/src/node/handler/PadMessageHandler.js b/src/node/handler/PadMessageHandler.js
index 060bca7b..1d9b5cf1 100644
--- a/src/node/handler/PadMessageHandler.js
+++ b/src/node/handler/PadMessageHandler.js
@@ -1153,6 +1153,82 @@ function handleClientReady(client, message)
         client.join(padIds.padId);
         //Save the revision in sessioninfos, we take the revision from the info the client send to us
         sessioninfos[client.id].rev = message.client_rev;
+
+        var changesetsNeeded = [];
+        var changesets = {};
+        var changesetsAuthor = {};
+        var changesetsTimestamp = {};
+
+        var startNum = message.client_rev + 1;
+        var endNum = pad.getHeadRevisionNumber() + 1;
+
+        async.series([
+          //fetch all changesets we need
+          function(callback)
+          {
+            var headNum = pad.getHeadRevisionNumber();
+            if (endNum > headNum+1)
+              endNum = headNum+1;
+            if (startNum < 0)
+              startNum = 0;
+            //create a array for all changesets, we will
+            //replace the values with the changeset later
+            for(var r=startNum;r<endNum;r++)
+            {
+              changesetsNeeded.push(r);
+            }
+            //get all changesets
+            async.forEach(changesetsNeeded, function(revNum)
+            {
+              pad.getRevisionChangeset(revNum, function(err, value)
+              {
+                if(ERR(err)) return;
+                changesets[revNum] = value;
+              });
+              pad.getRevisionAuthor(revNum, function(err, value)
+              {
+                if(ERR(err)) return;
+                changesetsAuthor[revNum] = value;
+              });
+              pad.getRevisionDate(revNum, function(err, value)
+              {
+                if(ERR(err)) return;
+                changesetsTimestamp[revNum] = value;
+              });
+            });
+            callback(null);
+          }
+        ],
+        //return err and changeset
+        function(err)
+        {
+          if(ERR(err, callback)) return;
+          async.eachSeries(changesetsNeeded, function(r)
+          {
+            var forWire = Changeset.prepareForWire(changesets[r], pad.pool);
+            var wireMsg = {"type":"COLLABROOM",
+                           "data":{type:"CLIENT_RECONNECT",
+                                   currRev: r,
+                                   newRev:pad.getHeadRevisionNumber(),
+                                   changeset:forWire.translated,
+                                   apool: forWire.pool,
+                                   author: changesetsAuthor[r],
+                                   currentTime: changesetsTimestamp[r]
+                           }};
+            client.json.send(wireMsg);
+           });
+          if (startNum == endNum)
+          {
+            var Msg = {"type":"COLLABROOM",
+                       "data":{type:"CLIENT_RECONNECT",
+                               noChanges: true,
+                               newRev:pad.getHeadRevisionNumber()
+                       }};
+
+            console.log("About to send client reconnect event");
+            client.json.send(Msg);
+          }
+        });
       }
       //This is a normal first connect
       else
diff --git a/src/static/js/collab_client.js b/src/static/js/collab_client.js
index 7cf98ae6..5259efd6 100644
--- a/src/static/js/collab_client.js
+++ b/src/static/js/collab_client.js
@@ -60,6 +60,8 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
   var debugMessages = [];
   var msgQueue = [];
 
+  var socketIOError = false;
+
   tellAceAboutHistoricalAuthors(serverVars.historicalAuthorData);
   tellAceActiveAuthorInfo(initialUserInfo);
 
@@ -181,7 +183,8 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
     }
 
     var sentMessage = false;
-    if (getSocket().realConnected) {
+    if (getSocket().realConnected && !socketIOError)
+    {
         var userChangesData = editor.prepareUserChangeset();
         if (userChangesData.changeset)
         {
@@ -198,9 +201,10 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
           callbacks.onInternalAction("commitPerformed");
         }
     }
-    else {
-        // run again in a few seconds, to check if there was a reconnection attempt
-        setTimeout(wrapRecordingErrors("setTimeout(handleUserChanges)", handleUserChanges), 1000);
+    else
+    {
+        // run again in a few seconds, to detect a reconnect
+        setTimeout(wrapRecordingErrors("setTimeout(handleUserChanges)", handleUserChanges), 3000);
     }
 
     if (sentMessage)
@@ -336,6 +340,44 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
       });
       handleUserChanges();
     }
+    else if (msg.type == 'CLIENT_RECONNECT')
+    {
+      if (msg.noChanges)
+      {
+        socketIOError = false;
+        return;
+      }
+
+      var currRev = msg.currRev;
+      var newRev = msg.newRev;
+      var changeset = msg.changeset;
+      var author = (msg.author || '');
+      var apool = msg.apool;
+
+
+      if (rev + 1 == currRev)
+      {
+        if (author == pad.getUserId())
+        {
+          editor.applyPreparedChangesetToBase();
+          setStateIdle();
+        }
+        else
+        {
+          editor.applyChangesToBase(changeset, author, apool);
+        }
+
+      }
+      if (rev + 1 < currRev)
+      {
+        editor.applyChangesToBase(changeset, author, apool);
+      }
+      if (currRev == newRev)
+      {
+        socketIOError = false;
+        rev = newRev;
+      }
+    }
     else if (msg.type == "NO_COMMIT_PENDING")
     {
       if (state == "COMMITTING")
@@ -597,6 +639,10 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
     schedulePerhapsCallIdleFuncs();
   }
 
+  function setSocketIOError(value)
+  {
+    socketIOError = value;
+  }
   function callWhenNotCommitting(func)
   {
     idleFuncs.push(func);
@@ -663,7 +709,8 @@ function getCollabClient(ace2editor, serverVars, initialUserInfo, options, _pad)
     callWhenNotCommitting: callWhenNotCommitting,
     addHistoricalAuthors: tellAceAboutHistoricalAuthors,
     setChannelState: setChannelState,
-    setStateIdle: setStateIdle
+    setStateIdle: setStateIdle,
+    setSocketIOError: setSocketIOError
   };
 
   $(document).ready(setUpSocket);
diff --git a/src/static/js/pad.js b/src/static/js/pad.js
index 9abedd27..38f8bfeb 100644
--- a/src/static/js/pad.js
+++ b/src/static/js/pad.js
@@ -209,11 +209,12 @@ function handshake()
   socket.on('reconnect', function () {
     socket.realConnected = true;
     pad.collabClient.setChannelState("CONNECTED");
-    pad.sendClientReady(true);
+    pad.sendClientReady(receivedClientVars);
   });
 
   socket.on('reconnecting', function() {
     socket.realConnected = false;
+    pad.collabClient.setStateIdle();
     pad.collabClient.setChannelState("RECONNECTING");
   });
 
@@ -224,6 +225,7 @@ function handshake()
   socket.on('error', function(error) {
     socket.realConnected = false;
     pad.collabClient.setStateIdle();
+    pad.collabClient.setSocketIOError(true);
   });
 
   var initalized = false;