server.py

from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from typing import List
import uvicorn
import json
import sqlite3

app = FastAPI()

conn = sqlite3.connect("chat.db", check_same_thread=False)
cursor = conn.cursor()

cursor.execute("""
CREATE TABLE IF NOT EXISTS messages (
    id INTEGER PRIMARY KEY,
    name TEXT,
    text TEXT,
    timestamp DATETIME DEFAULT CURRENT_TIMESTAMP
)
""")

conn.commit()


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 broadcast(self, message: str):

        for connection in self.active_connections:
            await connection.send_text(message)


manager = ConnectionManager()


@app.websocket("/chat")
async def websocket_endpoint(websocket: WebSocket):

    await manager.connect(websocket)

    cursor.execute(
        "SELECT id, name, text FROM messages ORDER BY id DESC LIMIT 50"
    )

    rows = cursor.fetchall()

    for msg_id, name, text in reversed(rows):
        await websocket.send_text(json.dumps({
            "id": msg_id,
            "name": name,
            "text": text
        }))

    # tell client history is finished
    await websocket.send_text(json.dumps({
        "type": "history_end"
    }))

    try:

        while True:
            data = await websocket.receive_text()

            message = json.loads(data)
            
            msg_type = message.get("type")
            if msg_type == "delete":
                msg_id = message.get("id")

                cursor.execute("DELETE FROM messages WHERE id=?", (msg_id,))
                conn.commit()

                await manager.broadcast(json.dumps({
                    "type": "delete",
                    "id": msg_id
                }))
                continue

            msg_id = message.get("id")
            name = message.get("name")
            text = message.get("text")

            cursor.execute(
                "INSERT INTO messages (id, name, text) VALUES (?, ?, ?)",
                (msg_id, name, text)
            )

            conn.commit()

            await manager.broadcast(json.dumps(message))

    except WebSocketDisconnect:

        manager.disconnect(websocket)


if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000)