"""Service des fichiers statiques du frontend (SPA) par FastAPI.

Le build Vite est copie dans `settings.static_dir`. Toute route qui n'est ni
/api/... ni un fichier existant retourne index.html, afin que le routeur
cote client puisse gerer /map/:id et /s/:token.
"""

from __future__ import annotations

import logging
from pathlib import Path

from fastapi import APIRouter, FastAPI, Request
from fastapi.responses import FileResponse, HTMLResponse, JSONResponse
from fastapi.staticfiles import StaticFiles

logger = logging.getLogger(__name__)

_PLACEHOLDER = """<!doctype html>
<html lang="fr"><head><meta charset="utf-8"><title>Frontend non compile</title></head>
<body style="font-family:system-ui;padding:2rem;max-width:40rem;margin:auto">
<h1>Frontend non compile</h1>
<p>L'API est disponible sur <code>/api/health</code>.</p>
<p>En developpement, lancez <code>npm run dev</code> dans <code>frontend/</code>.</p>
</body></html>"""

# Fichiers servis a la racine et qui ne doivent pas etre mis en cache longtemps.
_NO_CACHE_FILES = {"index.html", "sw.js", "manifest.webmanifest"}


def _safe_resolve(static_dir: Path, relative_path: str) -> Path | None:
    """Empeche toute sortie du dossier statique (path traversal)."""
    candidate = (static_dir / relative_path.lstrip("/")).resolve()
    try:
        candidate.relative_to(static_dir.resolve())
    except ValueError:
        return None
    return candidate


def mount_frontend(app: FastAPI, static_dir_path: str) -> None:
    static_dir = Path(static_dir_path)
    router = APIRouter(include_in_schema=False)

    if (static_dir / "assets").is_dir():
        # Les assets Vite sont hashes : cache long sans risque.
        app.mount(
            "/assets",
            StaticFiles(directory=static_dir / "assets"),
            name="assets",
        )

    @router.api_route("/{full_path:path}", methods=["GET", "HEAD"])
    def serve_spa(full_path: str, request: Request):  # type: ignore[no-untyped-def]
        if full_path.startswith("api/"):
            return JSONResponse(status_code=404, content={"detail": "Ressource introuvable."})

        if not static_dir.is_dir():
            return HTMLResponse(_PLACEHOLDER, status_code=200)

        if full_path:
            candidate = _safe_resolve(static_dir, full_path)
            if candidate is not None and candidate.is_file():
                headers = (
                    {"Cache-Control": "no-cache"}
                    if candidate.name in _NO_CACHE_FILES
                    else {"Cache-Control": "public, max-age=3600"}
                )
                return FileResponse(candidate, headers=headers)

        index = static_dir / "index.html"
        if index.is_file():
            return FileResponse(index, headers={"Cache-Control": "no-cache"})
        return HTMLResponse(_PLACEHOLDER, status_code=200)

    app.include_router(router)