import { useState, type FormEvent } from 'react';
import { useMutation } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';
import { Link, useLocation, useNavigate } from 'react-router';

import { login } from '@/api/auth';
import { ErrorNotice } from '@/components/ui/ErrorNotice';
import { Field } from '@/components/ui/Field';
import { Button, Card } from '@/components/ui/primitives';
import { getQueryClient } from '@/lib/queryClient';
import { useInstance } from '@/lib/hooks';
import { errorCode } from '@/lib/format';

interface LocationState {
  from?: string;
}

/** Форма входа: поле кода 2FA появляется при ответе `auth.2fa_required`. */
export default function LoginPage() {
  const { t } = useTranslation();
  const navigate = useNavigate();
  const location = useLocation();
  const instance = useInstance();

  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [totpCode, setTotpCode] = useState('');
  const [needsTotp, setNeedsTotp] = useState(false);

  const from = (location.state as LocationState | null)?.from ?? '/app';

  const submit = useMutation({
    mutationFn: () =>
      login(needsTotp ? { email, password, totp_code: totpCode } : { email, password }),
    onSuccess: async () => {
      // Профиль перечитываем заново: cookie уже выставлена сервером.
      await getQueryClient().invalidateQueries();
      void navigate(from === '/login' ? '/app' : from, { replace: true });
    },
    onError: (error: unknown) => {
      if (errorCode(error) === 'auth.2fa_required') {
        setNeedsTotp(true);
      }
    },
  });

  const onSubmit = (event: FormEvent<HTMLFormElement>): void => {
    event.preventDefault();
    submit.mutate();
  };

  const registrationEnabled = instance.data?.registration_enabled === true;

  return (
    <main className="mx-auto flex min-h-full w-full max-w-md flex-col justify-center gap-5 px-4 py-10">
      <header>
        <h1 className="text-2xl font-semibold tracking-tight">{t('auth.login.title')}</h1>
        <p className="mt-1 text-fg-muted">{t('auth.login.subtitle')}</p>
      </header>

      <Card>
        <form className="flex flex-col gap-4" onSubmit={onSubmit} noValidate>
          <Field
            label={t('auth.login.email')}
            type="email"
            name="email"
            autoComplete="username"
            placeholder={t('auth.login.emailPlaceholder')}
            value={email}
            onChange={(event) => setEmail(event.target.value)}
            required
          />
          <Field
            label={t('auth.login.password')}
            type="password"
            name="password"
            autoComplete="current-password"
            value={password}
            onChange={(event) => setPassword(event.target.value)}
            required
          />
          {needsTotp ? (
            <Field
              label={t('auth.login.totp')}
              hint={t('auth.login.totpHint')}
              name="totp_code"
              inputMode="numeric"
              autoComplete="one-time-code"
              pattern="[0-9]*"
              maxLength={8}
              value={totpCode}
              onChange={(event) => setTotpCode(event.target.value)}
              autoFocus
            />
          ) : null}

          {submit.isError ? <ErrorNotice error={submit.error} /> : null}

          <Button type="submit" disabled={submit.isPending}>
            {t(submit.isPending ? 'auth.login.submitting' : 'auth.login.submit')}
          </Button>
        </form>

        <p className="mt-4 text-sm text-fg-muted">
          {t('auth.login.noAccount')}{' '}
          {registrationEnabled ? (
            <Link className="text-accent underline" to="/register">
              {t('auth.login.registerLink')}
            </Link>
          ) : (
            <span>{t('auth.login.registrationDisabled')}</span>
          )}
        </p>
        <p className="mt-2 text-xs text-fg-muted">{t('auth.login.forgot')}</p>
      </Card>

      <footer className="flex items-center justify-between text-xs text-fg-muted">
        <Link className="underline" to="/status">
          {t('auth.login.instanceStatus')}
        </Link>
        <span>{instance.data?.version ?? ''}</span>
      </footer>
    </main>
  );
}