remotelink-docker/relay/main.py

"""
RemoteLink WebSocket Relay
Bridges agent (remote machine) ↔ viewer (browser) connections.

Agent connects:  ws://relay:8765/ws/agent?machine_id=<uuid>&access_key=<hex>
Viewer connects: ws://relay:8765/ws/viewer?session_id=<uuid>&viewer_token=<uuid>
"""

import asyncio
import json
import logging
import os
from contextlib import asynccontextmanager
from typing import Optional
from uuid import UUID

import asyncpg
from fastapi import FastAPI, WebSocket, WebSocketDisconnect, Query, HTTPException
from fastapi.middleware.cors import CORSMiddleware

logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")
log = logging.getLogger("relay")

DATABASE_URL = os.environ["DATABASE_URL"]
# Comma-separated list of allowed origins for CORS, e.g. "https://app.example.com"
ALLOWED_ORIGINS = [o.strip() for o in os.environ.get("ALLOWED_ORIGINS", "").split(",") if o.strip()]

# ── In-memory connection registry ────────────────────────────────────────────
# machine_id (str) → WebSocket
agents: dict[str, WebSocket] = {}
# session_id (str) → WebSocket
viewers: dict[str, WebSocket] = {}
# session_id → machine_id
session_to_machine: dict[str, str] = {}
# session_id → viewer's user role ("admin" | "user")
viewer_roles: dict[str, str] = {}

db_pool: Optional[asyncpg.Pool] = None


@asynccontextmanager
async def lifespan(app: FastAPI):
    global db_pool
    db_pool = await asyncpg.create_pool(DATABASE_URL, min_size=2, max_size=10)
    log.info("Database pool ready")
    yield
    await db_pool.close()


app = FastAPI(lifespan=lifespan)

app.add_middleware(
    CORSMiddleware,
    allow_origins=ALLOWED_ORIGINS if ALLOWED_ORIGINS else ["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


# ── Helpers ───────────────────────────────────────────────────────────────────

async def validate_agent(machine_id: str, access_key: str) -> Optional[dict]:
    async with db_pool.acquire() as conn:
        row = await conn.fetchrow(
            "SELECT id, name, user_id FROM machines WHERE id = $1 AND access_key = $2",
            machine_id, access_key,
        )
    return dict(row) if row else None


async def validate_viewer(session_id: str, viewer_token: str) -> Optional[dict]:
    async with db_pool.acquire() as conn:
        row = await conn.fetchrow(
            """SELECT s.id, s.machine_id, s.machine_name, COALESCE(u.role, 'user') AS viewer_role
               FROM sessions s
               LEFT JOIN users u ON u.id = s.viewer_user_id
               WHERE s.id = $1 AND s.viewer_token = $2 AND s.ended_at IS NULL""",
            session_id, viewer_token,
        )
    return dict(row) if row else None


async def set_machine_online(machine_id: str, online: bool):
    async with db_pool.acquire() as conn:
        await conn.execute(
            "UPDATE machines SET is_online = $1, last_seen = now() WHERE id = $2",
            online, machine_id,
        )


async def send_json(ws: WebSocket, data: dict):
    try:
        await ws.send_text(json.dumps(data))
    except Exception:
        pass


# ── Agent WebSocket endpoint ──────────────────────────────────────────────────

@app.websocket("/ws/agent")
async def agent_endpoint(
    websocket: WebSocket,
    machine_id: str = Query(...),
    access_key: str = Query(...),
):
    machine = await validate_agent(machine_id, access_key)
    if not machine:
        await websocket.close(code=4001, reason="Unauthorized")
        return

    await websocket.accept()
    agents[machine_id] = websocket
    await set_machine_online(machine_id, True)
    log.info(f"Agent connected: {machine['name']} ({machine_id})")

    try:
        while True:
            msg = await websocket.receive()

            # Client sent a close frame — exit cleanly
            if msg.get("type") == "websocket.disconnect":
                break

            if "bytes" in msg and msg["bytes"]:
                # Binary = JPEG frame → forward to all viewers watching this machine
                frame_data = msg["bytes"]
                for sid, mid in list(session_to_machine.items()):
                    if mid == machine_id and sid in viewers:
                        try:
                            await viewers[sid].send_bytes(frame_data)
                        except Exception:
                            viewers.pop(sid, None)
                            session_to_machine.pop(sid, None)

            elif "text" in msg and msg["text"]:
                # JSON message from agent (script output, status, etc.)
                try:
                    data = json.loads(msg["text"])
                    # Forward script output to the relevant viewer
                    if data.get("type") == "script_output":
                        session_id = data.get("session_id")
                        if session_id and session_id in viewers:
                            await send_json(viewers[session_id], data)
                    elif data.get("type") == "ping":
                        await set_machine_online(machine_id, True)
                except json.JSONDecodeError:
                    pass

    except WebSocketDisconnect:
        pass
    except Exception as e:
        log.warning(f"Agent {machine_id} error: {e}")
    finally:
        agents.pop(machine_id, None)
        await set_machine_online(machine_id, False)
        # Notify any connected viewers that the agent disconnected
        for sid, mid in list(session_to_machine.items()):
            if mid == machine_id and sid in viewers:
                await send_json(viewers[sid], {"type": "agent_disconnected"})
        log.info(f"Agent disconnected: {machine['name']} ({machine_id})")


# ── Viewer WebSocket endpoint ─────────────────────────────────────────────────

@app.websocket("/ws/viewer")
async def viewer_endpoint(
    websocket: WebSocket,
    session_id: str = Query(...),
    viewer_token: str = Query(...),
):
    session = await validate_viewer(session_id, viewer_token)
    if not session:
        await websocket.close(code=4001, reason="Session not found or expired")
        return

    machine_id = str(session["machine_id"]) if session["machine_id"] else None
    if not machine_id:
        await websocket.close(code=4002, reason="No machine associated with session")
        return

    viewer_role = session.get("viewer_role", "user")

    await websocket.accept()
    viewers[session_id] = websocket
    session_to_machine[session_id] = machine_id
    viewer_roles[session_id] = viewer_role
    log.info(f"Viewer connected to session {session_id} (machine {machine_id}, role {viewer_role})")

    if machine_id in agents:
        # Tell agent to start streaming for this session
        await send_json(agents[machine_id], {
            "type": "start_stream",
            "session_id": session_id,
        })
        await send_json(websocket, {"type": "agent_connected", "machine_name": session["machine_name"]})
    else:
        await send_json(websocket, {"type": "agent_offline"})

    try:
        while True:
            text = await websocket.receive_text()
            try:
                event = json.loads(text)
                event["session_id"] = session_id
                # exec_script is restricted to admin viewers only
                if event.get("type") == "exec_script":
                    if viewer_roles.get(session_id) != "admin":
                        await send_json(websocket, {
                            "type": "error",
                            "message": "exec_script requires admin role",
                        })
                        continue
                # Forward control events to the agent
                if machine_id in agents:
                    await send_json(agents[machine_id], event)
            except json.JSONDecodeError:
                pass
    except WebSocketDisconnect:
        pass
    except Exception as e:
        log.warning(f"Viewer {session_id} error: {e}")
    finally:
        viewers.pop(session_id, None)
        session_to_machine.pop(session_id, None)
        viewer_roles.pop(session_id, None)
        if machine_id in agents:
            await send_json(agents[machine_id], {"type": "stop_stream", "session_id": session_id})
        log.info(f"Viewer disconnected from session {session_id}")


# ── Health / status endpoints ─────────────────────────────────────────────────

@app.get("/health")
async def health():
    return {"status": "ok", "agents": len(agents), "viewers": len(viewers)}


@app.get("/status/{machine_id}")
async def machine_status(machine_id: str):
    return {"online": machine_id in agents}