'use client';

import Link from 'next/link';
import { useEffect, useState } from 'react';
import { useParams, useSearchParams } from 'next/navigation';
import { api } from '@/lib/api';
import { resolveAuthCallbackURL } from '@/lib/auth-redirect';
import { signIn } from '@/lib/auth-client';
import type { SsoProviderDiscovery } from '@/lib/sso';

export default function AuthProviderRedirectPage(): React.ReactElement {
  const params = useParams<{ provider: string }>();
  const searchParams = useSearchParams();
  const providerId = typeof params.provider === 'string' ? params.provider : '';
  const requestedCallbackURL = searchParams.get('callbackURL');
  const [providerName, setProviderName] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    let cancelled = false;

    async function redirectToProvider(): Promise<void> {
      try {
        const callbackURL = resolveAuthCallbackURL(requestedCallbackURL, window.location.origin);
        const providers = await api<SsoProviderDiscovery[]>('/api/sso/providers');
        if (cancelled) return;

        const provider = providers.find((candidate) => candidate.id === providerId);
        if (!provider) {
          setError('Unknown SSO provider.');
          return;
        }

        setProviderName(provider.name);
        if (!provider.configured) {
          setError(`${provider.name} is not enabled in this deployment.`);
          return;
        }
        if (provider.loginMode !== 'oidc') {
          setError(`${provider.name} is not available for OIDC sign in.`);
          return;
        }

        const result = await signIn.oauth2({
          providerId: provider.id,
          callbackURL,
        });

        if (!cancelled && result?.error) {
          setError(result.error.message ?? `${provider.name} sign in failed.`);
        }
      } catch (caught: unknown) {
        if (!cancelled) {
          setError(caught instanceof Error ? caught.message : 'Unable to start single sign-on.');
        }
      }
    }

    void redirectToProvider();

    return () => {
      cancelled = true;
    };
  }, [providerId, requestedCallbackURL]);

  return (
    <div className="mx-auto flex min-h-[50vh] max-w-md flex-col justify-center">
      <h1 className="text-2xl font-semibold text-text-primary">Single sign-on</h1>
      <p className="mt-2 text-sm text-text-secondary">
        {providerName
          ? `Redirecting you to ${providerName}...`
          : 'Preparing your sign-in request...'}
      </p>

      {error ? (
        <div
          role="alert"
          className="mt-6 rounded-lg border border-error/30 bg-error/10 px-4 py-3 text-sm text-error"
        >
          <p>{error}</p>
          <Link
            href="/login"
            className="mt-3 inline-block font-medium text-blue-400 hover:text-blue-300"
          >
            Return to login
          </Link>
        </div>
      ) : (
        <div className="mt-6 rounded-lg border border-surface-border bg-surface-elevated px-4 py-3 text-sm text-text-secondary">
          If the redirect does not start automatically, return to the login page and try again.
        </div>
      )}
    </div>
  );
}