"""Instructor routes (single-session deployment).

The deployment runs exactly one quiz session at a time, loaded from
`QUIZ_POOL_PATH` at startup. There is no per-quiz CRUD; the operator
edits the pool JSON on disk and restarts the service when they want
a new pool. The admin UI is therefore a thin control panel for the
single canonical session whose id is `Settings.default_session_id`.
"""

from __future__ import annotations

from pathlib import Path

from fastapi import APIRouter, HTTPException, Request, Response, WebSocket
from fastapi.responses import FileResponse, PlainTextResponse

from app import auth
from app.config import Settings
from app.csv_export import export_session_csv
from app.models import AdminLoginRequest
from app.rate_limit import TokenBucket, client_ip
from app.room import RoomManager, _qr_data_url


def router(settings: Settings, rooms: RoomManager) -> APIRouter:
    api = APIRouter()

    # Per-app instance so test apps get fresh state.
    # 10 attempts/minute/IP — generous for the instructor, hostile to brute
    # force without locking out the campus network on student endpoints
    # (which are not rate-limited at all, see rate_limit.py).
    login_bucket = TokenBucket(capacity=10, refill_per_minute=10)

    def require_admin(request: Request) -> None:
        auth.require_admin_request(settings, request)

    @api.post("/admin/login")
    async def login(body: AdminLoginRequest, request: Request, response: Response):
        ip = client_ip(request)
        if not login_bucket.take(ip):
            raise HTTPException(
                status_code=429,
                detail="Too many login attempts; try again in a minute.",
            )
        if not auth.verify_admin_password(settings, body.password):
            raise HTTPException(status_code=401, detail="Invalid admin password")
        auth.set_admin_cookie(settings, response, auth.sign_admin(settings))
        return {"ok": True}

    @api.post("/admin/logout")
    async def logout(response: Response):
        response.delete_cookie(auth.ADMIN_COOKIE, path="/")
        return {"ok": True}

    @api.get("/admin/")
    async def admin_page():
        # No auth gate; the SPA fetches /admin/api/state and renders
        # the login form on 401 or the dashboard on 200.
        return FileResponse(Path("static/admin.html"))

    @api.get("/admin/api/state")
    async def admin_state(request: Request):
        require_admin(request)
        sid = rooms.canonical_sid or settings.default_session_id
        if not await rooms.session_exists(sid):
            raise HTTPException(status_code=503, detail="Session is not initialised")
        session = await rooms.get_session(sid)
        pool = await rooms.get_pool_for_session(sid)
        join_url = f"{settings.public_url}/?sid={sid}"
        return {
            "sid": sid,
            "title": session["title"],
            "state": session["state"],
            "current_question_idx": session["current_question_idx"],
            "join_url": join_url,
            "qr_url": _qr_data_url(join_url),
            "pool_meta": {
                "score_fn": pool["score_fn"],
                "time_limit_default": pool["time_limit_default"],
                "question_count": len(pool["questions"]),
            },
        }

    @api.post("/admin/api/reset")
    async def admin_reset(request: Request):
        require_admin(request)
        sid = rooms.canonical_sid or settings.default_session_id
        if not await rooms.session_exists(sid):
            raise HTTPException(status_code=503, detail="Session is not initialised")
        await rooms.reset(sid)
        return {"ok": True}

    @api.delete("/admin/api/students/{student_id}")
    async def admin_clear_student(student_id: str, request: Request):
        # Recovery hatch for first-claim-wins: if a student lost their
        # cookie or their id was hijacked, the instructor can free the
        # slot here. Removes the participant + all of their submissions
        # and kicks any active WS for that id; the legitimate student
        # then re-joins via the normal flow.
        require_admin(request)
        sid = rooms.canonical_sid or settings.default_session_id
        if not await rooms.session_exists(sid):
            raise HTTPException(status_code=503, detail="Session is not initialised")
        removed = await rooms.clear_student(sid, student_id)
        if not removed:
            raise HTTPException(status_code=404, detail="No such student in session")
        return {"ok": True}

    @api.get("/admin/api/csv")
    async def csv_download(request: Request):
        require_admin(request)
        sid = rooms.canonical_sid or settings.default_session_id
        if not await rooms.session_exists(sid):
            raise HTTPException(status_code=503, detail="Session is not initialised")
        csv_text = await export_session_csv(settings.db_path, sid)
        return PlainTextResponse(
            csv_text,
            media_type="text/csv",
            headers={"Content-Disposition": f'attachment; filename="{sid}-results.csv"'},
        )

    @api.websocket("/ws/instructor/{sid}")
    async def instructor_socket(websocket: WebSocket, sid: str):
        if not auth.is_admin_ws(settings, websocket) or not await rooms.session_exists(sid):
            await websocket.close(code=4001)
            return
        await rooms.instructor_ws(websocket, sid)

    return api