"use client";

import { LogOutIcon, RefreshCwIcon } from "lucide-react";
import Link from "next/link";
import { usePathname } from "next/navigation";
import { useEffect, useState } from "react";
import { AdminSessionProvider } from "@/components/admin/AdminSession";
import { SubscriptionsDialog } from "@/components/admin/SubscriptionsDialog";
import { Button } from "@/components/ui/button";
import { Skeleton } from "@/components/ui/skeleton";
import { Toaster } from "@/components/ui/sonner";
import { goToAdminLogin, signOut } from "@/lib/admin-auth";
import { api, ApiError } from "@/lib/api";
import type { AdminUser } from "@/lib/types";

type Failure = "denied" | "unavailable";

export default function AdminLayout({ children }: { children: React.ReactNode }) {
  const pathname = usePathname();
  // /admin/login sits under this layout too, and must not be gated: it is the
  // forwarder signed-out visitors are sent to. Gating it would hand the admin
  // app the forwarder's own URL as the return target - so signing in would
  // land back on the forwarder, which forwards again.
  const isLoginPage = pathname === "/admin/login";
  const [me, setMe] = useState<AdminUser | null>(null);
  const [failure, setFailure] = useState<Failure | null>(null);

  // The one call that decides whether the admin area renders. proxy.ts already
  // bounced visitors with no cookie at all, but only the API can tell a valid
  // session from a stale one, or a colleague without the calendar permission
  // from one who has it.
  //
  // Exactly one status sends the user to the login page: 401. Anything else
  // means they may well be signed in already, and bouncing them would sign them
  // in, return them here and fail again - an endless loop with nothing on
  // screen to explain it, triggered by exactly the partial outage most likely
  // just after a deploy. 403 is the permission case; everything else (500, the
  // API's 503 when the admin database is down, a network or CORS failure as
  // status 0) is a fault worth showing.
  useEffect(() => {
    if (isLoginPage) return;
    api
      .me()
      .then((user) => {
        // Signed in, but not for this app. The API would refuse every write,
        // so say so once instead of failing per action.
        if (!user.apps.includes("calendar")) {
          setFailure("denied");
          return;
        }
        setMe(user);
      })
      .catch((e: unknown) => {
        const status = e instanceof ApiError ? e.status : 0;
        if (status === 401) {
          goToAdminLogin();
          return;
        }
        setFailure(status === 403 ? "denied" : "unavailable");
      });
  }, [isLoginPage]);

  if (isLoginPage) {
    return <>{children}</>;
  }

  if (failure) {
    return <FailureScreen failure={failure} />;
  }

  return (
    <div className="flex min-h-dvh flex-col">
      <header className="sticky top-0 z-30 border-b bg-background/90 pt-[env(safe-area-inset-top)] backdrop-blur supports-[backdrop-filter]:bg-background/75">
        <div className="mx-auto flex h-14 w-full max-w-4xl items-center justify-between gap-3 px-4 sm:px-6">
          <Link href="/admin" className="flex items-baseline gap-2">
            <span className="font-semibold tracking-tight">Nachklang</span>
            <span className="text-sm text-muted-foreground">Kalender</span>
          </Link>
          <div className="flex items-center gap-1 sm:gap-3">
            {me ? (
              <span className="hidden max-w-48 truncate text-sm text-muted-foreground sm:inline">{me.fullName}</span>
            ) : (
              <Skeleton className="hidden h-4 w-24 sm:block" />
            )}
            {me && <SubscriptionsDialog />}
            <Button variant="ghost" size="sm" onClick={() => void signOut()} aria-label="Abmelden">
              <LogOutIcon />
              <span className="hidden sm:inline">Abmelden</span>
            </Button>
          </div>
        </div>
      </header>

      <main className="mx-auto w-full max-w-4xl flex-1 px-4 pt-4 pb-[calc(6rem+env(safe-area-inset-bottom))] sm:px-6 sm:pt-6">
        {me ? <AdminSessionProvider value={me}>{children}</AdminSessionProvider> : <LoadingShell />}
      </main>
      <Toaster position="top-center" />
    </div>
  );
}

/** What the page looks like while /me is in flight - the list's shape, not a blank page. */
function LoadingShell() {
  return (
    <div className="flex flex-col gap-3" aria-busy="true" aria-label="Wird geladen">
      <Skeleton className="h-9 w-full" />
      <Skeleton className="h-5 w-32" />
      {Array.from({ length: 4 }, (_, i) => (
        <Skeleton key={i} className="h-20 w-full" />
      ))}
    </div>
  );
}

function FailureScreen({ failure }: { failure: Failure }) {
  const denied = failure === "denied";
  return (
    <div className="mx-auto flex min-h-dvh max-w-md flex-col items-center justify-center gap-4 px-6 text-center">
      <h1 className="text-lg font-semibold">{denied ? "Kein Zugriff auf den Kalender" : "Kalender nicht erreichbar"}</h1>
      <p className="text-sm text-muted-foreground">
        {denied
          ? "Dein Konto ist angemeldet, hat aber keine Berechtigung für den Kalender. Eine Administratorin oder ein Administrator kann sie dir in der Verwaltung geben – danach die Seite neu laden."
          : "Die Verwaltung ist gerade nicht erreichbar. Bitte lade die Seite in einem Moment neu."}
      </p>
      <div className="flex flex-wrap justify-center gap-2">
        <Button variant="outline" onClick={() => window.location.reload()}>
          <RefreshCwIcon />
          Neu laden
        </Button>
        {denied && (
          <Button variant="ghost" onClick={() => void signOut()}>
            <LogOutIcon />
            Abmelden
          </Button>
        )}
      </div>
    </div>
  );
}