"use client";

import React from "react";
import { RefreshCw } from "lucide-react";
import { usePathname, useRouter } from "next/navigation";

import { useAuth } from "@/components/auth/authContext";
import {
	shouldRedirectToProfileForPasswordChange,
	buildMustChangePasswordRedirectUrl,
	resolveMustChangePasswordResumePath,
} from "@/lib/frontend/auth/mustChangePasswordGate";
import { Button } from "@/components/ui/button";
import { Alert, AlertTitle, AlertDescription } from "@/components/ui/alert";
import {
	Card,
	CardHeader,
	CardTitle,
	CardDescription,
	CardContent,
	CardFooter,
} from "@/components/ui/card";

export default function AuthGate({ children }) {
	const router = useRouter();
	const pathname = usePathname() || "/";

	const { status, user, error, retry } = useAuth();

	const canRetry = typeof retry === "function";
	const isAuthenticated = status === "authenticated" && user;
	const mustChangePassword = isAuthenticated && user.mustChangePassword === true;

	const currentSearch =
		typeof window !== "undefined" ? window.location.search || "" : "";
	const currentPathWithSearch = `${pathname}${currentSearch}`;
	const mustChangePasswordRedirectUrl = buildMustChangePasswordRedirectUrl(
		currentPathWithSearch,
	);

	const shouldForceProfileRedirect = isAuthenticated
		? shouldRedirectToProfileForPasswordChange({
				pathname,
				mustChangePassword,
			})
		: false;

	const resumePathAfterPasswordChange = isAuthenticated
		? resolveMustChangePasswordResumePath({
				pathname,
				searchParams:
					typeof window !== "undefined"
						? new URLSearchParams(window.location.search || "")
						: null,
				mustChangePassword,
			})
		: null;

	React.useEffect(() => {
		if (!shouldForceProfileRedirect) return;
		router.replace(mustChangePasswordRedirectUrl);
	}, [shouldForceProfileRedirect, mustChangePasswordRedirectUrl, router]);

	React.useEffect(() => {
		if (!resumePathAfterPasswordChange) return;
		router.replace(resumePathAfterPasswordChange);
	}, [resumePathAfterPasswordChange, router]);

	if (status === "authenticated") {
		if (shouldForceProfileRedirect) return null;
		if (resumePathAfterPasswordChange) return null;

		return children;
	}

	if (status === "error") {
		return (
			<Card>
				<CardHeader>
					<CardTitle>Sitzungsprüfung fehlgeschlagen</CardTitle>
					<CardDescription>
						Die Sitzung konnte nicht geprüft werden.
					</CardDescription>
				</CardHeader>

				<CardContent className="space-y-3">
					<Alert variant="destructive">
						<AlertTitle>Fehler</AlertTitle>
						<AlertDescription>
							{error ||
								"Bitte prüfen Sie Ihre Verbindung und versuchen Sie es erneut."}
						</AlertDescription>
					</Alert>
				</CardContent>

				<CardFooter className="flex flex-col gap-2 sm:flex-row sm:justify-end">
					<Button
						type="button"
						variant="outline"
						onClick={() => {
							if (canRetry) retry();
							else window.location.reload();
						}}
					>
						<RefreshCw className="h-4 w-4" />
						Erneut versuchen
					</Button>
				</CardFooter>
			</Card>
		);
	}

	// "unauthenticated" -> redirect happens in AuthProvider.
	// Keeping this message is fine because TopNav indicator is not shown in this state.
	if (status === "unauthenticated") {
		return (
			<Card>
				<CardHeader>
					<CardTitle>Weiterleitung</CardTitle>
					<CardDescription>
						Sie werden zum Login weitergeleitet.
					</CardDescription>
				</CardHeader>

				<CardContent>
					<p className="text-sm text-muted-foreground">Bitte warten…</p>
				</CardContent>
			</Card>
		);
	}

	// Default: loading (or unknown)
	// RHL-032:
	// Do not render a second "session checking" UI here.
	// The TopNav SessionIndicator is the single source of feedback.
	return null;
}