main.py

import json
from fastapi import FastAPI, Request, WebSocket, WebSocketDisconnect
from fastapi.responses import HTMLResponse
from fastapi.staticfiles import StaticFiles
from fastapi.templating import Jinja2Templates
from pydantic import BaseModel

app = FastAPI()

app.mount("/static", StaticFiles(directory="static"), name="static")
templates = Jinja2Templates(directory= "templates")

class ConnectionManager:
    def __init__(self):
        self.active_connections: list[WebSocket] = []

    async def connect(self, websocket: WebSocket):
        await websocket.accept()
        self.active_connections.append(websocket)

    def disconnect(self, websocket: WebSocket):
        self.active_connections.remove(websocket)

    async def send_personal_message(self, message: str, websocket: WebSocket):
        await websocket.send_text(message)

    async def emit_message(self, message: str, websocket: WebSocket):
        for connection in self.active_connections:
            if connection !=  websocket:
                await connection.send_text(message)
    async def broadcast(self, message: str):
        for connection in self.active_connections:
            await connection.send_text(message)

manager = ConnectionManager()

@app.get('/', response_class = HTMLResponse)
async def root(request:Request):
    return templates.TemplateResponse("index.html", {"request": request})

@app.websocket('/draw')
async def websocket_endpoint(websocket: WebSocket):
    await manager.connect(websocket)
    try:
        while True:
            data = await websocket.receive_text()
            await manager.emit_message(data, websocket)
    except WebSocketDisconnect:
        manager.disconnect(websocket)