"""Display — WebSocket frame streaming + REST app management for GUI apps.

Pattern mirrors terminal.py: WebSocket attaches to a running GUI app,
receives JPEG frames, sends input events. REST endpoints manage app lifecycle.
"""

import logging
from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Query, WebSocket, WebSocketDisconnect
from pydantic import BaseModel

from backend.auth import get_current_user, ws_authenticate
from backend.display import display_manager, HAS_DISPLAY_DEPS

router = APIRouter(prefix="/api/display", tags=["display"])
log = logging.getLogger("atlus.display.router")


# ---------------------------------------------------------------------------
# Guards
# ---------------------------------------------------------------------------

def _require_deps():
    if not HAS_DISPLAY_DEPS:
        raise HTTPException(503, "Display dependencies not installed (Xvfb, xdotool, ImageMagick)")


# ---------------------------------------------------------------------------
# REST — app lifecycle
# ---------------------------------------------------------------------------

class AppLaunchRequest(BaseModel):
    command: str
    title: str = ""
    args: list[str] = []
    target_fps: int = 10


@router.get("/apps")
async def list_apps(user: str = Depends(get_current_user)):
    """List running GUI apps for the current user."""
    _require_deps()
    return {"apps": display_manager.list_apps(user)}


@router.post("/apps")
async def launch_app(req: AppLaunchRequest, user: str = Depends(get_current_user)):
    """Launch a GUI application on the user's virtual display."""
    _require_deps()

    # Check if this command is already running
    existing = display_manager.get_app_by_command(user, req.command)
    if existing:
        return existing.to_dict()

    try:
        app = await display_manager.launch_app(
            user, req.command, req.title, req.args, req.target_fps,
        )
        return app.to_dict()
    except ValueError as e:
        raise HTTPException(400, str(e))
    except FileNotFoundError as e:
        raise HTTPException(404, str(e))
    except RuntimeError as e:
        raise HTTPException(500, str(e))


@router.delete("/apps/{app_id}")
async def close_app(app_id: str, user: str = Depends(get_current_user)):
    """Stop a running GUI application."""
    _require_deps()
    if not display_manager.close_app(user, app_id):
        raise HTTPException(404, "App not found")
    return {"ok": True}


@router.get("/status")
async def display_status(user: str = Depends(get_current_user)):
    """Check display system availability."""
    return {
        "available": HAS_DISPLAY_DEPS,
        "apps": display_manager.list_apps(user),
    }


# ---------------------------------------------------------------------------
# WebSocket — frame streaming + input
# ---------------------------------------------------------------------------

@router.websocket("/ws")
async def display_ws(
    websocket: WebSocket,
    app_id: str = Query(default=None),
):
    """Attach to a GUI app's window — receive JPEG frames, send input.

    Query params:
      - app_id: required — the GUI app to stream
      - token: auth token (handled by ws_authenticate)

    Server sends:
      - Binary: raw JPEG frame bytes
      - {"type": "meta", "app_id": "...", "title": "...", "command": "..."}
      - {"type": "closed", "data": "Application exited"}
      - {"type": "error", "data": "..."}

    Client sends:
      - {"type": "mouse", "action": "click|dblclick|move|scroll",
         "x": N, "y": N, "button": 1, "delta": N}
      - {"type": "key", "action": "press|release",
         "key": "a", "code": "KeyA", "modifiers": ["ctrl"]}
      - {"type": "set_fps", "fps": 15}
    """
    username = await ws_authenticate(websocket)
    await websocket.accept()

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

    app = display_manager.get_app(username, app_id)
    if not app:
        await websocket.send_json({"type": "error", "data": "App not found"})
        await websocket.close(code=4004)
        return

    # Send metadata
    await websocket.send_json({
        "type": "meta",
        "app_id": app.app_id,
        "title": app.title,
        "command": app.command,
    })

    # Send last captured frame for instant display on reconnect
    if app.last_frame:
        await websocket.send_bytes(app.last_frame)

    app.attach_ws(websocket)
    log.info("WebSocket attached to app %s (%s) for %s", app_id, app.command, username)

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

            if msg_type in ("mouse", "key"):
                await app.send_input(msg)
            elif msg_type == "set_fps":
                fps = msg.get("fps", 10)
                app.target_fps = max(1, min(30, fps))
    except WebSocketDisconnect:
        pass
    except Exception:
        log.exception("Display WS error for %s/%s", username, app_id)
    finally:
        app.detach_ws(websocket)
        log.info("WebSocket detached from app %s for %s", app_id, username)