import 'package:eatvio_app/core/theme/custom_text_style.dart';
import 'package:eatvio_app/core/theme/theme_helper.dart';
import 'package:eatvio_app/core/widgets/bottom_sheet_handler_bar.dart';
import 'package:eatvio_app/features/payment/models/promo_code_model.dart';
import 'package:eatvio_app/generated/l10n.dart';
import 'package:flutter/material.dart';

/// Результат работы модалки промокода.
class PromoCodeResult {
  const PromoCodeResult({
    this.code,
    this.discountPercent,
    this.discountAmountRub,
    this.originalAmountRub,
    this.finalAmountRub,
    this.alreadyApplied = false,
  });

  /// Применённый промокод или null, если пользователь продолжил без него.
  final String? code;
  final int? discountPercent;
  final double? discountAmountRub;
  final double? originalAmountRub;
  final double? finalAmountRub;

  /// true — промокод уже на сервере (rehydrate Continue), apply не нужен.
  final bool alreadyApplied;

  bool get hasPromoCode => code != null;
}

/// Ответ проверки промокода.
class PromoValidation {
  const PromoValidation.success({
    this.discountPercent,
    this.discountAmountRub,
    this.originalAmountRub,
    this.finalAmountRub,
  }) : error = null;

  const PromoValidation.failure(this.error)
      : discountPercent = null,
        discountAmountRub = null,
        originalAmountRub = null,
        finalAmountRub = null;

  final String? error;
  final int? discountPercent;
  final double? discountAmountRub;
  final double? originalAmountRub;
  final double? finalAmountRub;

  bool get isValid => error == null;
}

/// Модальное окно ввода / просмотра применённого промокода.
class ItvioPromoCodeModal extends StatefulWidget {
  const ItvioPromoCodeModal({
    super.key,
    this.onValidate,
    this.onRemove,
    this.initialPromo,
  });

  final Future<PromoValidation> Function(String code)? onValidate;
  final Future<bool> Function()? onRemove;
  final PromoCodeModel? initialPromo;

  static Future<PromoCodeResult?> show(
    BuildContext context, {
    Future<PromoValidation> Function(String code)? onValidate,
    Future<bool> Function()? onRemove,
    PromoCodeModel? initialPromo,
  }) {
    return showModalBottomSheet<PromoCodeResult>(
      context: context,
      isScrollControlled: true,
      useSafeArea: true,
      backgroundColor: Colors.transparent,
      builder: (_) => ItvioPromoCodeModal(
        onValidate: onValidate,
        onRemove: onRemove,
        initialPromo: initialPromo,
      ),
    );
  }

  @override
  State<ItvioPromoCodeModal> createState() => _ItvioPromoCodeModalState();
}

enum _ModalState { input, loading, applied }

class _ItvioPromoCodeModalState extends State<ItvioPromoCodeModal> {
  final _controller = TextEditingController();
  final _focusNode = FocusNode();

  late _ModalState _state;
  String? _errorText;
  int? _discountPercent;
  double? _discountAmountRub;
  String? _appliedCode;

  @override
  void initState() {
    super.initState();
    final initial = widget.initialPromo;
    if (initial != null) {
      _state = _ModalState.applied;
      _appliedCode = initial.promoCode;
      _discountPercent = initial.discountPercent;
      _discountAmountRub = initial.discountAmountRub;
      _controller.text = initial.promoCode;
    } else {
      _state = _ModalState.input;
    }
  }

  @override
  void dispose() {
    _controller.dispose();
    _focusNode.dispose();
    super.dispose();
  }

  Future<void> _apply() async {
    final code = _controller.text.trim().toUpperCase();

    if (code.isEmpty) {
      setState(() => _errorText = S.of(context).enter_promo_code);
      return;
    }

    setState(() {
      _state = _ModalState.loading;
      _errorText = null;
    });

    PromoValidation validation;
    try {
      validation = widget.onValidate != null
          ? await widget.onValidate!(code)
          : const PromoValidation.success();
    } catch (_) {
      validation = const PromoValidation.failure(
        'Не удалось проверить промокод. Попробуйте позже',
      );
    }

    if (!mounted) return;

    if (!validation.isValid) {
      setState(() {
        _state = _ModalState.input;
        _errorText = validation.error;
      });
      _focusNode.requestFocus();
      return;
    }

    Navigator.of(context).pop(
      PromoCodeResult(
        code: code,
        discountPercent: validation.discountPercent,
        discountAmountRub: validation.discountAmountRub,
        originalAmountRub: validation.originalAmountRub,
        finalAmountRub: validation.finalAmountRub,
      ),
    );
  }

  void _onContinueApplied() {
    Navigator.of(context).pop(
      PromoCodeResult(
        code: _appliedCode,
        discountPercent: _discountPercent,
        discountAmountRub: _discountAmountRub,
        alreadyApplied: true,
      ),
    );
  }

  Future<void> _onRemove() async {
    setState(() {
      _state = _ModalState.loading;
      _errorText = null;
    });

    var success = true;
    try {
      if (widget.onRemove != null) {
        success = await widget.onRemove!();
      }
    } catch (_) {
      success = false;
    }

    if (!mounted) return;

    if (!success) {
      setState(() {
        _state = _ModalState.applied;
        _errorText = S.of(context).promo_remove_failed;
      });
      return;
    }

    setState(() {
      _state = _ModalState.input;
      _appliedCode = null;
      _discountPercent = null;
      _discountAmountRub = null;
      _errorText = null;
      _controller.clear();
    });
    _focusNode.requestFocus();
  }

  void _onSkip() {
    Navigator.of(context).pop(const PromoCodeResult());
  }

  bool get _isLoading => _state == _ModalState.loading;

  /// Applied UI while loading remove (state=loading, but promo still shown).
  bool get _isApplied =>
      _appliedCode != null && _state != _ModalState.input;

  @override
  Widget build(BuildContext context) {
    final bottomInset = MediaQuery.of(context).viewInsets.bottom;
    final s = S.of(context);

    return Padding(
      padding: EdgeInsets.only(bottom: bottomInset),
      child: Container(
        width: double.infinity,
        decoration: const BoxDecoration(
          color: Colors.white,
          borderRadius: BorderRadius.vertical(top: Radius.circular(20)),
        ),
        padding: const EdgeInsets.fromLTRB(20, 8, 20, 20),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            const Center(child: BottomSheetHandlerBar()),
            const SizedBox(height: 16),
            _buildHeader(s),
            if (_isApplied) ...[
              const SizedBox(height: 6),
              Text(
                s.promo_applied_subtitle,
                style: const TextStyle(fontSize: 14, color: Color(0xFF6B7684)),
              ),
            ],
            const SizedBox(height: 16),
            Text(
              s.promo_code,
              style: const TextStyle(
                fontSize: 13,
                color: Color(0xFF6B7684),
              ),
            ),
            const SizedBox(height: 8),
            _buildField(s),
            const SizedBox(height: 8),
            _buildHint(s),
            const SizedBox(height: 12),
            if (_isApplied) ...[
              _buildContinueButton(s),
              const SizedBox(height: 6),
              _buildRemoveButton(s),
            ] else ...[
              _buildApplyButton(s),
              const SizedBox(height: 6),
              _buildSkipButton(s),
            ],
          ],
        ),
      ),
    );
  }

  Widget _buildHeader(S s) {
    return Text(
      _isApplied ? s.promo_applied_title : s.have_promo_code_form,
      style: TextStyles.headingXLSemibold.copyWith(color: appTheme.black),
    );
  }

  Widget _buildField(S s) {
    final hasError = _errorText != null && !_isApplied;

    return AnimatedContainer(
      duration: const Duration(milliseconds: 150),
      decoration: BoxDecoration(
        color: appTheme.gray100,
        borderRadius: BorderRadius.circular(12),
        border: Border.all(
          width: 2,
          color: hasError
              ? appTheme.red
              : (_focusNode.hasFocus && !_isApplied
                  ? appTheme.blueA400
                  : Colors.transparent),
        ),
      ),
      child: Row(
        children: [
          Expanded(
            child: TextField(
              controller: _controller,
              focusNode: _focusNode,
              enabled: !_isLoading && !_isApplied,
              textCapitalization: TextCapitalization.characters,
              onChanged: (_) {
                if (_errorText != null) {
                  setState(() => _errorText = null);
                }
              },
              onSubmitted: (_) {
                if (!_isApplied) _apply();
              },
              decoration: InputDecoration(
                hintText: s.enter_promo_code,
                hintStyle: const TextStyle(
                  color: Color(0xFF9AA3AF),
                ),
                border: InputBorder.none,
                isDense: true,
                contentPadding: const EdgeInsets.symmetric(
                  horizontal: 16,
                  vertical: 14,
                ),
              ),
              style: TextStyle(
                fontSize: 15,
                color: _isApplied
                    ? const Color(0xFF6B7684)
                    : const Color(0xFF24303F),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildHint(S s) {
    final String text;
    final Color color;

    if (_errorText != null) {
      text = _errorText!;
      color = appTheme.red;
    } else if (_isApplied && _discountPercent != null) {
      final amount = (_discountAmountRub ?? 0).toStringAsFixed(0);
      text = s.promo_discount_hint(_discountPercent!, amount);
      color = const Color(0xFF27A06B);
    } else {
      text = '';
      color = Colors.transparent;
    }

    return SizedBox(
      height: 19,
      child: Text(
        text,
        style: TextStyle(fontSize: 13, color: color),
        overflow: TextOverflow.ellipsis,
      ),
    );
  }

  Widget _buildApplyButton(S s) {
    return SizedBox(
      height: 50,
      child: FilledButton(
        onPressed: _isLoading ? null : _apply,
        style: FilledButton.styleFrom(
          backgroundColor: appTheme.blueA400,
          foregroundColor: appTheme.whiteA700,
          disabledBackgroundColor: appTheme.blueA400.withValues(alpha: 0.55),
          shape: const StadiumBorder(),
          textStyle: const TextStyle(
            fontSize: 15,
            fontWeight: FontWeight.w600,
          ),
        ),
        child: _isLoading
            ? const SizedBox(
                width: 20,
                height: 20,
                child: CircularProgressIndicator(
                  strokeWidth: 2.5,
                  color: Colors.white,
                ),
              )
            : Text(s.apply),
      ),
    );
  }

  Widget _buildContinueButton(S s) {
    return SizedBox(
      height: 50,
      child: FilledButton(
        onPressed: _isLoading ? null : _onContinueApplied,
        style: FilledButton.styleFrom(
          backgroundColor: appTheme.blueA400,
          foregroundColor: appTheme.whiteA700,
          disabledBackgroundColor: appTheme.blueA400.withValues(alpha: 0.55),
          shape: const StadiumBorder(),
          textStyle: const TextStyle(
            fontSize: 15,
            fontWeight: FontWeight.w600,
          ),
        ),
        child: Text(s.continue_),
      ),
    );
  }

  Widget _buildRemoveButton(S s) {
    return SizedBox(
      height: 46,
      child: TextButton(
        onPressed: _isLoading ? null : _onRemove,
        style: TextButton.styleFrom(
          foregroundColor: appTheme.blueA400,
          shape: const StadiumBorder(),
          textStyle: const TextStyle(fontSize: 14),
        ),
        child: _isLoading
            ? SizedBox(
                width: 20,
                height: 20,
                child: CircularProgressIndicator(
                  strokeWidth: 2.5,
                  color: appTheme.blueA400,
                ),
              )
            : Text(s.promo_remove),
      ),
    );
  }

  Widget _buildSkipButton(S s) {
    return SizedBox(
      height: 46,
      child: TextButton(
        onPressed: _isLoading ? null : _onSkip,
        style: TextButton.styleFrom(
          foregroundColor: appTheme.blueA400,
          shape: const StadiumBorder(),
          textStyle: const TextStyle(fontSize: 14),
        ),
        child: Text(s.skip),
      ),
    );
  }
}