import 'package:flutter/cupertino.dart';
import 'package:please_pay_me/core/branding/app_brand.dart';
import 'package:please_pay_me/data/api/api_client.dart';
import 'package:please_pay_me/features/auth/session_controller.dart';
import 'package:please_pay_me/features/auth/telegram_login.dart';
import 'package:please_pay_me/features/auth/yandex_login.dart';
import 'package:please_pay_me/features/legal/legal_consent.dart';
import 'package:please_pay_me/theme/theme.dart';
import 'package:please_pay_me/ui/ui.dart';
import 'package:provider/provider.dart';

/// Opens the cabinet and returns the harvested JWT.
typedef TelegramLoginLauncher = Future<String?> Function(
  BuildContext context,
  String cabinetUrl,
);

/// Opens Yandex OAuth and returns the JWT issued by `/api/auth/yandex`.
typedef YandexLoginLauncher = Future<String?> Function(
  BuildContext context, {
  required String clientId,
  required String redirectUri,
});

/// Sign-in screen.
///
/// Cabinet / API origin comes from `.env` (`PPM_WEB_URL`, `PPM_API_BASE_URL`).
/// Telegram: cabinet WebView + JWT channel. Yandex: OAuth code in a WebView,
/// exchanged on the API so the client secret never leaves the server.
class LoginScreen extends StatefulWidget {
  const LoginScreen({
    super.key,
    this.launchTelegramLogin,
    this.launchYandexLogin,
  });

  /// Injection point for tests and Widgetbook, where no WebView exists.
  final TelegramLoginLauncher? launchTelegramLogin;
  final YandexLoginLauncher? launchYandexLogin;

  @override
  State<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  final _tokenController = TextEditingController();

  bool _busy = false;
  late bool _tokenMode = !_webLoginAvailable;
  YandexAuthProvider? _yandex;
  String? _providersError;
  LegalAcceptance _legal = const LegalAcceptance();

  bool get _webLoginAvailable =>
      widget.launchTelegramLogin != null || isTelegramWebLoginSupported;

  bool get _yandexLoginAvailable =>
      widget.launchYandexLogin != null || isYandexWebLoginSupported;

  String _cabinetUrl(SessionController session) {
    if (session.webCabinetUrl.isNotEmpty) return session.webCabinetUrl;
    return session.baseUrl;
  }

  String _apiBase(SessionController session) {
    return resolveApiBaseUrl(
      cabinetUrl: _cabinetUrl(session),
      configuredApiBaseUrl: session.configuredApiBaseUrl,
    );
  }

  @override
  void initState() {
    super.initState();
    _loadProviders();
  }

  @override
  void dispose() {
    _tokenController.dispose();
    super.dispose();
  }

  Future<void> _loadProviders() async {
    final session = context.read<SessionController>();
    final apiBase = _apiBase(session);
    if (apiBase.isEmpty) {
      if (mounted) {
        setState(() {
          _providersError = 'Не задан PPM_API_BASE_URL в .env';
        });
      } else {
        _providersError = 'Не задан PPM_API_BASE_URL в .env';
      }
      return;
    }

    try {
      final providers = await fetchAuthProviders(apiBase, httpClient: session.httpClient);
      if (!mounted) return;
      setState(() {
        _yandex = providers.yandex;
        _providersError = providers.yandex?.usable == true
            ? null
            : 'API не включил Яндекс (нет YANDEX_CLIENT_ID/SECRET на сервере)';
      });
    } on ApiException catch (error) {
      if (!mounted) return;
      setState(() {
        _yandex = null;
        _providersError = error.message;
      });
    } catch (error) {
      if (!mounted) return;
      setState(() {
        _yandex = null;
        _providersError = error.toString();
      });
    }
  }

  Future<bool> _ensureCabinetUrl(SessionController session) async {
    if (_cabinetUrl(session).isNotEmpty) return true;
    await showAppToast(
      context,
      message: 'Задайте PPM_WEB_URL в mobile/.env',
      icon: CupertinoIcons.exclamationmark_circle_fill,
    );
    return false;
  }

  @override
  Widget build(BuildContext context) {
    final session = context.watch<SessionController>();

    return CupertinoPageScaffold(
      backgroundColor: AppColors.of(context, AppColors.groupedBackground),
      child: SafeArea(
        child: ListView(
          padding: const EdgeInsets.only(top: AppSpacing.s7, bottom: AppSpacing.s6),
          children: [
            const Padding(
              padding: EdgeInsets.symmetric(horizontal: AppSpacing.gutter),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  AppIcon(
                    CupertinoIcons.money_rubl_circle_fill,
                    size: 48,
                    color: AppColors.accent,
                  ),
                  SizedBox(height: AppSpacing.s3),
                  AppText.largeTitle(AppBrand.name),
                  SizedBox(height: AppSpacing.s1),
                  AppText.subhead(
                    'Бюджет от зарплаты до зарплаты. Войдите через Яндекс.',
                  ),
                ],
              ),
            ),
            const SizedBox(height: AppSpacing.s6),
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: AppSpacing.gutter),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  LegalConsentBlock(
                    value: _legal,
                    cabinetUrl: _cabinetUrl(session),
                    onChanged: (next) => setState(() => _legal = next),
                  ),
                  const SizedBox(height: AppSpacing.s5),
                  if (_tokenMode) ...[
                    AppTextField(
                      label: 'Токен доступа',
                      placeholder: 'eyJhbGciOi…',
                      controller: _tokenController,
                      enabled: !_busy,
                      errorText: session.lastError,
                    ),
                    const SizedBox(height: AppSpacing.s5),
                    AppButton(
                      label: 'Войти по токену',
                      loading: _busy,
                      onPressed: _legal.accepted ? _signInWithToken : null,
                    ),
                  ] else ...[
                    if (session.lastError != null) ...[
                      AppText.footnote(session.lastError!, color: AppColors.systemRed),
                      const SizedBox(height: AppSpacing.s3),
                    ],
                    const SizedBox(height: AppSpacing.s3),
                      AppButton(
                        label: 'Войти через Яндекс',
                        style: AppButtonStyle.gray,
                        loading: _busy,
                        onPressed: _legal.accepted ? _signInWithYandex : null,
                      ),
                  ],
                ],
              ),
            ),
            const SizedBox(height: AppSpacing.s5),
            const AppListSection(
              header: 'Что умеет',
              footer: 'Один кабинет на телефоне и в браузере — бюджет не разъедется.',
              children: [
                AppListTile(
                  leading: AppIcon(CupertinoIcons.calendar, color: AppColors.accent),
                  title: 'Бюджет от зарплаты до зарплаты',
                  subtitle: 'Остаток и дневной лимит на каждый день периода',
                  showChevron: false,
                ),
                AppListTile(
                  leading: AppIcon(CupertinoIcons.money_rubl, color: AppColors.accent),
                  title: 'Траты в один тап',
                  subtitle: 'Журнал по дням, несколько конвертов параллельно',
                  showChevron: false,
                ),
                AppListTile(
                  leading: AppIcon(CupertinoIcons.briefcase, color: AppColors.accent),
                  title: 'График выплат',
                  subtitle: 'Оклад, дни зарплаты и правило выходных',
                  showChevron: false,
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }

  Future<void> _signInWithTelegram() async {
    final session = context.read<SessionController>();
    if (!await _ensureCabinetUrl(session)) return;

    final cabinetUrl = _cabinetUrl(session);
    final launcher = widget.launchTelegramLogin ??
        (ctx, url) => showTelegramLogin(context: ctx, cabinetUrl: url);

    setState(() => _busy = true);
    final token = await launcher(context, cabinetUrl);

    if (!mounted) return;

    if (token == null || token.isEmpty) {
      setState(() => _busy = false);
      return;
    }

    await session.signInWithToken(baseUrl: _apiBase(session), token: token);
    if (mounted) setState(() => _busy = false);
  }

  Future<void> _signInWithYandex() async {
    final session = context.read<SessionController>();
    if (!await _ensureCabinetUrl(session)) return;

    if (_yandex == null || !(_yandex?.usable ?? false)) {
      setState(() => _busy = true);
      await _loadProviders();
      if (mounted) setState(() => _busy = false);
    }

    final provider = _yandex;
    if (provider == null || !provider.usable) {
      await showAppToast(
        context,
        message: _providersError ?? 'Вход через Яндекс недоступен',
        icon: CupertinoIcons.exclamationmark_circle_fill,
      );
      return;
    }

    if (!_yandexLoginAvailable) {
      await showAppToast(
        context,
        message: 'Яндекс в приложении работает на телефоне. На Windows откройте кабинет в браузере.',
        icon: CupertinoIcons.device_phone_portrait,
      );
      return;
    }

    final cabinetUrl = _cabinetUrl(session);
    final apiBase = _apiBase(session);
    final redirectUri = cabinetYandexRedirectUri(
      cabinetUrl,
      configured: provider.redirectUri,
    );

    setState(() => _busy = true);

    final launcher = widget.launchYandexLogin;
    final token = launcher != null
        ? await launcher(context, clientId: provider.clientId, redirectUri: redirectUri)
        : await showYandexLogin(
            context: context,
            clientId: provider.clientId,
            redirectUri: redirectUri,
            exchangeCode: (code) => exchangeYandexCode(
              apiBaseUrl: apiBase,
              code: code,
              redirectUri: redirectUri,
              httpClient: session.httpClient,
            ),
          );

    if (!mounted) return;

    if (token == null || token.isEmpty) {
      setState(() => _busy = false);
      return;
    }

    await session.signInWithToken(baseUrl: apiBase, token: token);
    if (mounted) setState(() => _busy = false);
  }

  Future<void> _signInWithToken() async {
    final session = context.read<SessionController>();
    if (!await _ensureCabinetUrl(session)) return;

    setState(() => _busy = true);
    await session.signInWithToken(
      baseUrl: _apiBase(session),
      token: _tokenController.text,
    );
    if (mounted) setState(() => _busy = false);
  }
}