"use client";

import React from "react";
import { useRouter } from "next/navigation";

import { login } from "@/lib/frontend/apiClient";
import { sanitizeNext } from "@/lib/frontend/authRedirect";
import {
	getLoginErrorMessage,
	getLoginReasonAlert,
} from "@/lib/frontend/authMessages";
import { homePath } from "@/lib/frontend/routes";

import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { Alert, AlertTitle, AlertDescription } from "@/components/ui/alert";
import {
	Card,
	CardHeader,
	CardTitle,
	CardDescription,
	CardContent,
	CardFooter,
} from "@/components/ui/card";

/**
 * LoginForm (RHL-020)
 *
 * Username casing policy:
 * - Our backend stores usernames in lowercase and performs lowercase normalization.
 * - To make UX consistent (and avoid "it works with BranchUser" confusion),
 *   we normalize the username input to lowercase in the UI as well.
 *
 * NOTE:
 * - Password is NOT normalized. It remains case-sensitive.
 *
 * UX rule:
 * - All user-facing text must be German.
 *
 * @param {{ reason: string|null, nextPath: string|null }} props
 */
export default function LoginForm({ reason, nextPath }) {
	const router = useRouter();

	// Controlled inputs.
	const [username, setUsername] = React.useState("");
	const [password, setPassword] = React.useState("");

	// UX state.
	const [isSubmitting, setIsSubmitting] = React.useState(false);
	const [errorMessage, setErrorMessage] = React.useState("");

	// Optional informational banner (session expired / logged-out).
	const reasonAlert = getLoginReasonAlert(reason);

	// Defensive: sanitize nextPath again on the client.
	const safeNext = sanitizeNext(nextPath) || homePath();

	async function onSubmit(e) {
		e.preventDefault();

		// Enforce our username policy at submit time as well (defense-in-depth).
		const u = username.trim().toLowerCase();
		const p = password; // do NOT normalize password

		if (!u || !p) {
			setErrorMessage("Bitte Benutzername und Passwort eingeben.");
			return;
		}

		setIsSubmitting(true);
		setErrorMessage("");

		try {
			await login({ username: u, password: p });
			router.replace(safeNext);
		} catch (err) {
			setErrorMessage(getLoginErrorMessage(err));
			setIsSubmitting(false);
		}
	}

	return (
		<Card>
			<CardHeader>
				<CardTitle>Anmeldung</CardTitle>
				<CardDescription>
					Bitte geben Sie Ihre Zugangsdaten ein, um die Lieferscheine zu öffnen.
				</CardDescription>
			</CardHeader>

			<CardContent className="space-y-4">
				{reasonAlert ? (
					<Alert>
						<AlertTitle>{reasonAlert.title}</AlertTitle>
						<AlertDescription>{reasonAlert.description}</AlertDescription>
					</Alert>
				) : null}

				{errorMessage ? (
					<Alert variant="destructive">
						<AlertTitle>Anmeldung fehlgeschlagen</AlertTitle>
						<AlertDescription>{errorMessage}</AlertDescription>
					</Alert>
				) : null}

				<form onSubmit={onSubmit} className="space-y-4">
					<div className="grid gap-2">
						<Label htmlFor="username">Benutzername</Label>
						<Input
							id="username"
							name="username"
							autoComplete="username"
							// Prevent mobile keyboards from auto-capitalizing the first character.
							autoCapitalize="none"
							autoCorrect="off"
							spellCheck={false}
							value={username}
							onChange={(e) => {
								// Normalize to lowercase as the user types (consistent UX).
								setUsername(e.target.value.toLowerCase());
							}}
							disabled={isSubmitting}
							placeholder="z. B. branchuser"
						/>
					</div>

					<div className="grid gap-2">
						<Label htmlFor="password">Passwort</Label>
						<Input
							id="password"
							name="password"
							type="password"
							autoComplete="current-password"
							value={password}
							onChange={(e) => setPassword(e.target.value)}
							disabled={isSubmitting}
							placeholder="••••••••"
						/>
					</div>

					<CardFooter className="p-0">
						<Button type="submit" className="w-full" disabled={isSubmitting}>
							{isSubmitting ? "Anmeldung…" : "Anmelden"}
						</Button>
					</CardFooter>
				</form>
			</CardContent>
		</Card>
	);
}
