"""Where a frontend is reachable from outside, as seen by one request."""

from __future__ import annotations

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from starlette.requests import Request

    from beaver_gateway.frontends.base import Frontend, GatewayRuntime


def request_origin(request: Request, runtime: GatewayRuntime) -> str:
    """``Gateway.public_url`` if configured, else the request's own origin."""
    if runtime.public_url:
        return runtime.public_url
    host = request.headers.get("host")
    if not host:
        return f"http://{request.url.hostname}:{request.url.port}"
    scheme = request.headers.get("x-forwarded-proto") or request.url.scheme
    return f"{scheme}://{host}"


def external_base(request: Request, runtime: GatewayRuntime) -> str:
    """Origin plus the mount path of the app handling ``request``."""
    return request_origin(request, runtime) + str(request.scope.get("root_path", ""))


def frontend_url(request: Request, runtime: GatewayRuntime, fe: Frontend) -> str | None:
    return request_origin(request, runtime) + fe.path if fe.path else None