"""The one ASGI app the gateway listens with.

Every HTTP frontend is mounted under its ``path`` (``/anthropic``,
``/mcp``, ``/md``, ``/api``, ``/admin``); ``/healthz`` answers for the
whole process and ``/`` redirects to the landing frontend (the admin
console) when one is configured.
"""

from __future__ import annotations

from typing import TYPE_CHECKING

from starlette.applications import Starlette
from starlette.responses import JSONResponse, RedirectResponse
from starlette.routing import Mount, Route

if TYPE_CHECKING:
    from collections.abc import Iterable

    from starlette.requests import Request

    from beaver_gateway.frontends.base import Frontend

__all__ = ["build_root_app"]


def build_root_app(frontends: Iterable[Frontend]) -> Starlette:
    mounted = [fe for fe in frontends if fe.path and fe.app() is not None]
    landing = next((fe for fe in mounted if fe.landing), None)
    paths = [fe.path for fe in mounted]

    async def healthz(_request: Request) -> JSONResponse:
        return JSONResponse({"status": "ok", "frontends": paths})

    async def index(_request: Request) -> JSONResponse | RedirectResponse:
        if landing is not None:
            return RedirectResponse(f"{landing.path}/", status_code=307)
        return JSONResponse({"frontends": paths})

    routes: list[Route | Mount] = [
        Route("/healthz", healthz, methods=["GET"]),
        Route("/", index, methods=["GET"]),
    ]
    for fe in mounted:
        app = fe.app()
        assert app is not None  # noqa: S101 - filtered above; narrows for ty
        assert fe.path is not None  # noqa: S101
        routes.append(Mount(fe.path, app=app, name=fe.name or fe.path.strip("/")))
    return Starlette(routes=routes)