import React from 'react';
import { useTranslation } from 'react-i18next';
import { useLocation, useNavigate } from 'react-router-dom';
import { Loader2 } from 'lucide-react';

import { Alert, AlertDescription } from '@/components/ui/alert';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Label } from '@/components/ui/label';

import { useAuth } from '../auth/context';
import { ADMIN_DEFAULT_AFTER_LOGIN_PATH, ADMIN_EVENTS_PATH } from '../constants';
import { resolveReturnTarget } from '../lib/returnTo';
import { useMutation } from '@tanstack/react-query';

type LoginResponse = {
  token: string;
  token_type: string;
  abilities: string[];
};

  async function performLogin(payload: { login: string; password: string; return_to?: string | null }): Promise<LoginResponse> {
  const response = await fetch('/api/v1/tenant-auth/login', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Accept': 'application/json',
    },
        body: JSON.stringify({
          ...payload,
          remember: true,
        }),
  });

  if (response.status === 422) {
    const data = await response.json();
    const errors = data.errors ?? {};
    const flattened = Object.values(errors).flat();
    throw new Error(flattened.join(' ') || 'Validation failed');
  }

  if (!response.ok) {
    throw new Error('Login failed.');
  }

  return (await response.json()) as LoginResponse;
}

export default function LoginPage(): React.ReactElement {
  const { status, applyToken, abilities } = useAuth();
  const { t } = useTranslation('auth');
  const location = useLocation();
  const navigate = useNavigate();

  const searchParams = React.useMemo(() => new URLSearchParams(location.search), [location.search]);
  const rawReturnTo = searchParams.get('return_to');

  const computeDefaultAfterLogin = React.useCallback(
    (abilityList?: string[]) => {
      const source = abilityList ?? abilities;
      return source.includes('tenant-admin') ? ADMIN_DEFAULT_AFTER_LOGIN_PATH : ADMIN_EVENTS_PATH;
    },
    [abilities],
  );

  const fallbackTarget = computeDefaultAfterLogin();
  const { finalTarget } = React.useMemo(
    () => resolveReturnTarget(rawReturnTo, fallbackTarget),
    [rawReturnTo, fallbackTarget]
  );

  React.useEffect(() => {
    if (status === 'authenticated') {
      navigate(finalTarget, { replace: true });
    }
  }, [finalTarget, navigate, status]);

  const [login, setLogin] = React.useState('');
  const [password, setPassword] = React.useState('');
  const [error, setError] = React.useState<string | null>(null);

  const mutation = useMutation({
    mutationKey: ['tenantAdminLogin'],
    mutationFn: performLogin,
    onError: (err: unknown) => {
      const message = err instanceof Error ? err.message : String(err);
      setError(message);
    },
    onSuccess: async (data) => {
      setError(null);
      await applyToken(data.token, data.abilities ?? []);
      const postLoginFallback = computeDefaultAfterLogin(data.abilities ?? []);
      const { finalTarget: successTarget } = resolveReturnTarget(rawReturnTo, postLoginFallback);
      navigate(successTarget, { replace: true });
    },
  });

  const isSubmitting = (mutation as { isPending?: boolean; isLoading?: boolean }).isPending
    ?? (mutation as { isPending?: boolean; isLoading?: boolean }).isLoading
    ?? false;

  const handleSubmit = (event: React.FormEvent<HTMLFormElement>) => {
    event.preventDefault();
    setError(null);

    mutation.mutate({
      login,
      password,
      return_to: rawReturnTo,
    });
  };

  return (
    <div className="relative min-h-svh overflow-hidden bg-slate-950 text-white">
      <div
        aria-hidden
        className="absolute inset-0 bg-[radial-gradient(ellipse_at_top,_rgba(255,137,170,0.35),_transparent_60%),radial-gradient(ellipse_at_bottom,_rgba(99,102,241,0.35),_transparent_55%)] blur-3xl"
      />
      <div className="absolute inset-0 bg-gradient-to-br from-gray-950 via-gray-950/70 to-[#1a0f1f]" aria-hidden />

      <div className="relative z-10 mx-auto flex w-full max-w-md flex-col gap-10 px-6 py-16">
        <header className="flex flex-col items-center gap-3 text-center">
          <span className="flex h-14 w-14 items-center justify-center overflow-hidden rounded-full border border-white/20 bg-white/10 shadow-lg shadow-black/20">
            <img
              src="/logo-transparent-md.png"
              alt={t('login.brand_alt', 'Fotospiel Logo')}
              className="h-12 w-12 object-contain"
              loading="lazy"
            />
          </span>
          <h1 className="text-2xl font-semibold tracking-tight">
            {t('login.panel_title', t('login.title', 'Team Login für Fotospiel'))}
          </h1>
          <p className="max-w-sm text-sm text-white/70">
            {t(
              'login.panel_copy',
              'Melde dich an, um Events zu planen, Fotos zu moderieren und Aufgaben im Fotospiel-Team zu koordinieren.'
            )}
          </p>
        </header>

        <form onSubmit={handleSubmit} className="flex flex-col gap-5 rounded-3xl border border-white/10 bg-white/95 p-8 text-slate-900 shadow-2xl shadow-rose-400/10 backdrop-blur-xl dark:border-white/10 dark:bg-slate-900/95 dark:text-slate-50">
          <div className="grid gap-2">
            <Label htmlFor="login" className="text-sm font-semibold text-slate-700 dark:text-slate-200">
              {t('login.username_or_email', 'E-Mail oder Benutzername')}
            </Label>
            <Input
              id="login"
              name="login"
              type="text"
              autoComplete="username"
              required
              value={login}
              onChange={(event) => setLogin(event.target.value)}
              className="h-12 rounded-xl border-slate-200/60 bg-white/90 px-4 text-base shadow-inner shadow-slate-200/40 focus-visible:ring-[#ff8bb1]/40 dark:border-slate-800/70 dark:bg-slate-900/70 dark:text-slate-100"
              placeholder={t('login.username_or_email_placeholder', 'name@example.com')}
            />
          </div>

          <div className="grid gap-2">
            <Label htmlFor="password" className="text-sm font-semibold text-slate-700 dark:text-slate-200">
              {t('login.password', 'Passwort')}
            </Label>
            <Input
              id="password"
              name="password"
              type="password"
              autoComplete="current-password"
              required
              value={password}
              onChange={(event) => setPassword(event.target.value)}
              className="h-12 rounded-xl border-slate-200/60 bg-white/90 px-4 text-base shadow-inner shadow-slate-200/40 focus-visible:ring-[#ff8bb1]/40 dark:border-slate-800/70 dark:bg-slate-900/70 dark:text-slate-100"
              placeholder={t('login.password_placeholder', '••••••••')}
            />
            <p className="text-xs text-slate-500 dark:text-slate-400">
              {t('login.remember_hint', 'Wir halten dich automatisch angemeldet, solange du dieses Gerät nutzt.')}
            </p>
          </div>

          {error ? (
            <Alert variant="destructive" className="rounded-2xl border-rose-400/50 bg-rose-50/90 text-rose-700 dark:border-rose-500/40 dark:bg-rose-500/10 dark:text-rose-100">
              <AlertDescription>{error}</AlertDescription>
            </Alert>
          ) : null}

          <Button
            type="submit"
            className={`mt-2 h-12 w-full justify-center rounded-xl bg-gradient-to-r from-[#ff5f87] via-[#ec4899] to-[#6366f1] text-base font-semibold shadow-[0_18px_35px_-18px_rgba(236,72,153,0.7)] transition hover:from-[#ff4470] hover:via-[#ec4899] hover:to-[#4f46e5] ${
              isSubmitting ? 'cursor-wait opacity-90 saturate-75 shadow-none' : ''
            }`}
            disabled={isSubmitting}
            aria-live="polite"
            aria-busy={isSubmitting}
            data-loading={isSubmitting ? 'true' : undefined}
          >
            <span className="flex w-full items-center justify-center gap-2">
              <Loader2
                className={`h-5 w-5 text-white transition-opacity ${isSubmitting ? 'animate-spin opacity-100' : 'opacity-0'}`}
                aria-hidden={!isSubmitting}
              />
              <span>{isSubmitting ? t('login.loading', 'Anmeldung …') : t('login.submit', 'Anmelden')}</span>
            </span>
          </Button>
        </form>

        <footer className="text-center text-xs text-white/50">
          {t('login.support', 'Fragen? Schreib uns an support@fotospiel.de oder antworte direkt auf deine Einladung.')}
        </footer>
      </div>
    </div>
  );
}