Handle wrong incoming order of nodes. The ids of new incoming nodes should not be higher than the var nextFreeId. Keep nodes in a buffer until the missing nodes arrive.

If a user leaves the collaborative editor, his remote cursors will stay in the editor.

The go backend knows when a replica leaves a session, the remote cursor of this replica should then be removed from the editor, because the replica is no longer active

At the moment only one editor exists which all collaborators use together. The content of the editor is present as long as the server is running.

A generator for unique links should be implemented. A user can create a new share-link and invite other users to this link to collaborate with him.

If all users leave the session, by closing the window or clicking on a button. The server deletes the session and its history. By organizing the requests in sessions its a good starting point to implement offline sessions of the users.

Host with unique access link/token
e.g.: localhost:8081/asdjf239023

• create unique links
• new users joining the link get the complete history
• users can define nick names, which are displayed as remote cursors
• improve UI of the session joining and creating process

Implement graceful shutdown by:

• cleaning/closing open streams
• closing channels

• handle Mass insertions as one node per line
• Split the node later if text is inserted/deleted
• Read additional papers to this topic

Think about how to implement mass deletions, if the text is not inserted by mass insertions and each char is a single node.

Reduce the time-/performance effort for CRDT

• implement bulk deletion/insertion
• enable login of new users. Go backend sends new users the stored event history
• improve performance for inserting nodes to the end of the line (the length a line needs to be transferred to crdt-backend) see #27
• handle offline sessions of individual replicas or of the go backend see #10
• improve local storage for chars

local bundle building with npm run build throws an error:

ERROR in ./node_modules/codemirror/theme/3024-night.css 11:0
Module parse failed: Unexpected token (11:0)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
| */
| 
> .cm-s-3024-night.CodeMirror { background: #090300; color: #d6d5d4; }
| .cm-s-3024-night div.CodeMirror-selected { background: #3a3432; }
| .cm-s-3024-night .CodeMirror-line::selection, .cm-s-3024-night .CodeMirror-line > span::selection, .cm-s-3024-night .CodeMirror-line > span > span::selection { background: rgba(58, 52, 50, .99); }
 @ ./src/main.js 6:0-41

ERROR in ./node_modules/codemirror/lib/codemirror.css 3:0
Module parse failed: Unexpected token (3:0)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
| /* BASICS */
| 
> .CodeMirror {
|   /* Set height, width, borders, and global font properties here */
|   font-family: monospace;
 @ ./src/main.js 5:0-39

Replace python "SimpleHTTPServer" with a better frontend-server, e.g. ngnix

Current python-server has a long startup time.

• find suitable cloud provider
• activated automated deployment for master branch

Find suitable implementations and optimizations in papers

Implement Linter: https://eslint.org

During creation of a new session the user can select for which language he wants syntax highlighting

• automated Protobuf compiling (for js and go)

use console.debug()

Transfer Input of one client to other client (other uses server-side-streaming for updates)

• use simple test field as input and

  as output (both clients see the same result)

• client subscribes at the server for updates
• client uses send button to transfer text object (send by button several times possible)

Replace the text area with the text editor library.

Usage and behavior for sending and receiving text remains constant.

https://codemirror.net/

Client can subscribe for updates at the server.

• Implement Keepalive

See:

• https://github.com/grpc/grpc/blob/master/doc/keepalive.md
• https://github.com/grpc/grpc-go/blob/master/examples/features/keepalive/client/main.go

• Determine the position as well as the character itself which has been inserted/deleted by the last user action
• create separate class for managing CRDT
• do transition function (a transition can be delete or insert)
• receive transition function (receives transition by server-side streaming and calls do transition)
• send transition function (sends transition by unary call)

Display the cursors of all users in the editor

• display a cursor object in CodeMirror with a unique user id
• [ ] listen cursor events in CodeMirror and send the new positions to the backend
• [ ] establish a server-side streaming connection to receive the cursor positions of the other users

Get familiar with the Events CodeMirror offers:

https://codemirror.net/doc/manual.html#events

Problem
The Server-side stream which serves the updates to all clients automatically closes after some time with the message "stream timeout". No automatic reconnection of the stream is happening.

Possible Solution
It would be an idea to send keep-alive pings from time to time from the go server to the clients.