"""Terminal WebSocket — attaches to persistent PTY sessions.

The PTY lifecycle is managed by backend.sessions.SessionManager.
WebSocket connections attach/detach without killing the PTY.
"""

import asyncio
import logging

from fastapi import APIRouter, WebSocket, WebSocketDisconnect, Query

from backend.auth import ws_authenticate
from backend.sessions import manager

router = APIRouter(tags=["terminal"])
log = logging.getLogger("atlus.terminal")


@router.websocket("/api/terminal/ws")
async def terminal_ws(
    websocket: WebSocket,
    terminal_id: str = Query(default=None),
):
    """Attach a WebSocket to an existing persistent terminal.

    Query params:
      - terminal_id: required — the terminal to attach to
      - token: auth token (handled by ws_authenticate)

    Client sends:
      - {"type": "input", "data": "..."} — keystrokes
      - {"type": "resize", "cols": N, "rows": N}

    Server sends:
      - {"type": "output", "data": "..."} — terminal output
      - {"type": "scrollback", "data": "..."} — initial scrollback replay
    """
    username = await ws_authenticate(websocket)
    await websocket.accept()

    if not terminal_id:
        await websocket.send_json({"type": "error", "data": "terminal_id required"})
        await websocket.close(code=4000)
        return

    terminal = manager.get_terminal(username, terminal_id)
    if not terminal or not terminal.alive:
        await websocket.send_json({"type": "error", "data": "Terminal not found or dead"})
        await websocket.close(code=4004)
        return

    # Send scrollback replay so the client sees previous output
    if terminal.scrollback:
        scrollback_text = "".join(terminal.scrollback)
        await websocket.send_json({"type": "scrollback", "data": scrollback_text})

    # Attach this WebSocket to receive live output
    terminal.attach_ws(websocket)
    log.info("WebSocket attached to terminal %s for %s", terminal_id, username)

    try:
        while True:
            msg = await websocket.receive_json()
            msg_type = msg.get("type")

            if msg_type == "input":
                if terminal.alive:
                    data = msg["data"]
                    if isinstance(data, str):
                        data = data.encode("utf-8")
                    terminal.pty.write(data)
            elif msg_type == "resize":
                if terminal.alive:
                    cols = msg.get("cols", 120)
                    rows = msg.get("rows", 30)
                    terminal.pty.setwinsize(rows, cols)
    except WebSocketDisconnect:
        pass
    except Exception:
        log.exception("terminal ws error for %s/%s", username, terminal_id)
    finally:
        terminal.detach_ws(websocket)
        log.info("WebSocket detached from terminal %s for %s", terminal_id, username)
        # PTY stays alive — no kill here