server.js

const express = require("express");
const http = require("http");
const socketIo = require("socket.io");
const path = require("path");

const crypto = require("crypto");
const serverId = crypto.randomUUID();

const redis = require("redis");

const pub = redis.createClient();
const sub = redis.createClient();

pub.connect();
sub.connect();

const app = express();
const server = http.createServer(app);
const io = socketIo(server);

const { applyOperation } = require("./ot/transform");

const connectDB = require("./db/connect");
connectDB();

app.use(express.static(path.join(__dirname, "public")));

io.on("connection", (socket) => {
  console.log("New client connected:", socket.id);
  const Document = require("./models/Document");
  socket.on("join_doc", async (docId) => {
    console.log(docId)              
    socket.join(docId);
    socket.docId = docId;

    let doc = await Document.findOne({ docId });
    if (!doc) {
      doc = await Document.create({ docId, content: "", version: 0 });
    }

    socket.emit("load_doc", {
      content: doc.content,
      version: doc.version,
    });
  });

  socket.on("text_change", async (incomingOp) => {
    const docId = socket.docId;
    if (!docId) return;

    const doc = await Document.findOne({ docId });
    if (!doc) return;

    const serverVersion = doc.version;
    const clientVersion = incomingOp.version;

    if (clientVersion !== serverVersion) {
      console.log(
        `Version mismatch (client: ${clientVersion}, server: ${serverVersion}) — ignoring op`
      );
      return;
    }

    const updatedContent = applyOperation(doc.content, incomingOp);
    doc.content = updatedContent;
    doc.version += 1;
    await doc.save();

    const opWithVersion = {
      op:      incomingOp.op,
      pos:     incomingOp.pos,
      char:    incomingOp.char,
      version: doc.version,
    };
    socket.to(docId).emit("receive_op", opWithVersion);

    await pub.publish("doc_changes", JSON.stringify({
      docId,
      op: opWithVersion,
      source: serverId, // tag this server as the source
    }));
    
    
  });

  socket.on("disconnect", () => {
    console.log("Client disconnected:", socket.id);
  });
});

sub.subscribe("doc_changes", (message) => {
  const { docId, op, source } = JSON.parse(message);

  if (source === serverId) return;

  io.to(docId).emit("receive_op", op);
});


const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`);
});