import { useEffect, useRef, useState } from 'react';
import { useTranslation } from 'react-i18next';
import { useQuery } from '@tanstack/react-query';
import { brandingApi, type TelegramWidgetConfig } from '../api/branding';
import { useAuthStore } from '../store/auth';
import { useNavigate } from 'react-router';

interface TelegramLoginButtonProps {
  referralCode?: string;
}

export default function TelegramLoginButton({ referralCode }: TelegramLoginButtonProps) {
  const { t } = useTranslation();
  const navigate = useNavigate();
  const containerRef = useRef<HTMLDivElement>(null);
  const [oidcLoading, setOidcLoading] = useState(false);
  const [oidcError, setOidcError] = useState('');
  const loginWithTelegramOIDC = useAuthStore((s) => s.loginWithTelegramOIDC);

  const { data: widgetConfig } = useQuery<TelegramWidgetConfig>({
    queryKey: ['telegram-widget-config'],
    queryFn: brandingApi.getTelegramWidgetConfig,
    staleTime: 60000,
  });

  const botUsername =
    widgetConfig?.bot_username || import.meta.env.VITE_TELEGRAM_BOT_USERNAME || '';
  const isOIDC = Boolean(widgetConfig?.oidc_enabled && widgetConfig?.oidc_client_id);

  // OIDC callback handler (ref pattern to avoid stale closures and unnecessary re-inits)
  const handleOIDCCallbackRef =
    useRef<(data: { id_token?: string; error?: string }) => void>(undefined);

  handleOIDCCallbackRef.current = async (data: { id_token?: string; error?: string }) => {
    if (data.error || !data.id_token) {
      setOidcError(data.error || t('auth.loginFailed'));
      setOidcLoading(false);
      return;
    }
    try {
      setOidcLoading(true);
      setOidcError('');
      await loginWithTelegramOIDC(data.id_token);
      navigate('/');
    } catch (err: unknown) {
      let message = t('common.error');
      if (err && typeof err === 'object' && 'response' in err) {
        const resp = (err as { response?: { data?: { detail?: string } } }).response;
        if (resp?.data?.detail) message = resp.data.detail;
      }
      setOidcError(message);
    } finally {
      setOidcLoading(false);
    }
  };

  // Load OIDC script and init
  useEffect(() => {
    if (!isOIDC || !widgetConfig?.oidc_client_id) return;

    const scriptId = 'telegram-login-oidc-script';
    let script = document.getElementById(scriptId) as HTMLScriptElement | null;

    const initTelegramLogin = () => {
      if (window.Telegram?.Login) {
        window.Telegram.Login.init(
          {
            client_id: Number(widgetConfig.oidc_client_id) || widgetConfig.oidc_client_id,
            request_access: widgetConfig.request_access ? ['write'] : undefined,
            lang: document.documentElement.lang || 'en',
          },
          (data) => handleOIDCCallbackRef.current?.(data),
        );
      }
    };

    if (!script) {
      script = document.createElement('script');
      script.id = scriptId;
      script.src = 'https://oauth.telegram.org/js/telegram-login.js?3';
      script.async = true;
      script.onload = initTelegramLogin;
      document.head.appendChild(script);
    } else {
      // Script already loaded, just re-init
      initTelegramLogin();
    }
  }, [isOIDC, widgetConfig?.oidc_client_id, widgetConfig?.request_access]);

  // Legacy widget effect (only when NOT OIDC)
  useEffect(() => {
    if (isOIDC || !containerRef.current || !botUsername || !widgetConfig) return;

    const container = containerRef.current;
    while (container.firstChild) {
      container.removeChild(container.firstChild);
    }

    const redirectUrl = `${window.location.origin}/auth/telegram/callback`;

    const script = document.createElement('script');
    script.src = 'https://telegram.org/js/telegram-widget.js?23';
    script.setAttribute('data-telegram-login', botUsername);
    script.setAttribute('data-size', widgetConfig.size);
    script.setAttribute('data-radius', String(widgetConfig.radius));
    script.setAttribute('data-userpic', String(widgetConfig.userpic));
    script.setAttribute('data-auth-url', redirectUrl);
    if (widgetConfig.request_access) {
      script.setAttribute('data-request-access', 'write');
    }
    script.async = true;

    container.appendChild(script);

    return () => {
      while (container.firstChild) {
        container.removeChild(container.firstChild);
      }
    };
  }, [isOIDC, botUsername, widgetConfig]);

  if (!botUsername || botUsername === 'your_bot') {
    return (
      <div className="py-4 text-center text-sm text-gray-500">
        {t('auth.telegramNotConfigured')}
      </div>
    );
  }

  return (
    <div className="flex flex-col items-center space-y-4">
      {/* OIDC mode: custom button that opens popup */}
      {isOIDC ? (
        <div className="flex flex-col items-center space-y-2">
          <button
            type="button"
            onClick={() => {
              setOidcError('');
              if (window.Telegram?.Login) {
                window.Telegram.Login.open();
              }
            }}
            disabled={oidcLoading}
            className="inline-flex items-center gap-2 rounded-lg bg-[#54a9eb] px-6 py-3 text-sm font-medium text-white shadow-sm transition-colors hover:bg-[#4a96d2] disabled:opacity-50"
          >
            <svg className="h-5 w-5" viewBox="0 0 24 24" fill="currentColor">
              <path d="M11.944 0A12 12 0 0 0 0 12a12 12 0 0 0 12 12 12 12 0 0 0 12-12A12 12 0 0 0 12 0a12 12 0 0 0-.056 0zm4.962 7.224c.1-.002.321.023.465.14a.506.506 0 0 1 .171.325c.016.093.036.306.02.472-.18 1.898-.962 6.502-1.36 8.627-.168.9-.499 1.201-.82 1.23-.696.065-1.225-.46-1.9-.902-1.056-.693-1.653-1.124-2.678-1.8-1.185-.78-.417-1.21.258-1.91.177-.184 3.247-2.977 3.307-3.23.007-.032.014-.15-.056-.212s-.174-.041-.249-.024c-.106.024-1.793 1.14-5.061 3.345-.48.33-.913.49-1.302.48-.428-.008-1.252-.241-1.865-.44-.752-.245-1.349-.374-1.297-.789.027-.216.325-.437.893-.663 3.498-1.524 5.83-2.529 6.998-3.014 3.332-1.386 4.025-1.627 4.476-1.635z" />
            </svg>
            {oidcLoading ? t('common.loading') : t('auth.loginWithTelegram')}
          </button>
          {oidcError && <p className="text-xs text-red-500">{oidcError}</p>}
        </div>
      ) : (
        /* Legacy widget mode: iframe-based widget */
        <div ref={containerRef} className="flex justify-center" />
      )}

      <div className="text-center">
        <p className="mb-2 text-xs text-gray-500">{t('auth.orOpenInApp')}</p>
        <a
          href={
            referralCode
              ? `https://t.me/${botUsername}?start=${encodeURIComponent(referralCode)}`
              : `https://t.me/${botUsername}`
          }
          target="_blank"
          rel="noopener noreferrer"
          className="text-telegram-blue inline-flex items-center text-sm hover:underline"
        >
          <svg className="mr-1 h-4 w-4" viewBox="0 0 24 24" fill="currentColor">
            <path d="M11.944 0A12 12 0 0 0 0 12a12 12 0 0 0 12 12 12 12 0 0 0 12-12A12 12 0 0 0 12 0a12 12 0 0 0-.056 0zm4.962 7.224c.1-.002.321.023.465.14a.506.506 0 0 1 .171.325c.016.093.036.306.02.472-.18 1.898-.962 6.502-1.36 8.627-.168.9-.499 1.201-.82 1.23-.696.065-1.225-.46-1.9-.902-1.056-.693-1.653-1.124-2.678-1.8-1.185-.78-.417-1.21.258-1.91.177-.184 3.247-2.977 3.307-3.23.007-.032.014-.15-.056-.212s-.174-.041-.249-.024c-.106.024-1.793 1.14-5.061 3.345-.48.33-.913.49-1.302.48-.428-.008-1.252-.241-1.865-.44-.752-.245-1.349-.374-1.297-.789.027-.216.325-.437.893-.663 3.498-1.524 5.83-2.529 6.998-3.014 3.332-1.386 4.025-1.627 4.476-1.635z" />
          </svg>
          @{botUsername}
        </a>
      </div>
    </div>
  );
}