import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../../app/providers.dart';
import '../../../core/constants/app_constants.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/utils/formatters.dart';
import '../../../core/widgets/numeric_keypad.dart';
import '../../../core/widgets/primary_button.dart';
import '../../../core/widgets/status_pill.dart';
import '../../../domain/entities/customer.dart';
import '../../pos/providers/cart_controller.dart';
import '../providers/customer_providers.dart';

/// Attaches a customer to the current bill using nothing but a mobile number.
///
/// Registration is deliberately minimal: an unknown number can be saved with
/// just a name, or the whole step skipped. Nothing here blocks the sale.
Future<void> showCustomerCaptureSheet(BuildContext context) {
  return showModalBottomSheet<void>(
    context: context,
    isScrollControlled: true,
    backgroundColor: Colors.transparent,
    builder: (_) => const _CustomerCaptureSheet(),
  );
}

class _CustomerCaptureSheet extends ConsumerStatefulWidget {
  const _CustomerCaptureSheet();

  @override
  ConsumerState<_CustomerCaptureSheet> createState() =>
      _CustomerCaptureSheetState();
}

class _CustomerCaptureSheetState
    extends ConsumerState<_CustomerCaptureSheet> {
  String _digits = '';
  final _name = TextEditingController();
  bool _saving = false;
  String? _error;

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

  void _append(String d) {
    if (_digits.length >= AppConstants.mobileNumberLength) return;
    setState(() {
      _digits += d;
      _error = null;
    });
    if (_digits.length == AppConstants.mobileNumberLength) {
      ref.read(customerLookupProvider.notifier).search(_digits);
    }
  }

  void _backspace() {
    if (_digits.isEmpty) return;
    setState(() => _digits = _digits.substring(0, _digits.length - 1));
    ref.read(customerLookupProvider.notifier).reset();
  }

  void _clear() {
    setState(() {
      _digits = '';
      _error = null;
    });
    ref.read(customerLookupProvider.notifier).reset();
  }

  void _attachAndClose(Customer? customer) {
    ref.read(cartControllerProvider.notifier).attachCustomer(customer);
    Navigator.of(context).pop();
  }

  Future<void> _quickRegister() async {
    final name = _name.text.trim();
    if (name.length < 2) {
      setState(() => _error = 'Enter a name to save this customer');
      return;
    }

    setState(() {
      _saving = true;
      _error = null;
    });

    try {
      final created = await ref.read(customerRepositoryProvider).create(
            Customer(id: '', name: name, mobile: _digits),
          );
      ref.invalidate(recentCustomersProvider);
      if (mounted) _attachAndClose(created);
    } catch (e) {
      if (!mounted) return;
      setState(() {
        _saving = false;
        _error = e is StateError ? e.message : 'Could not save customer.';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    final lookup = ref.watch(customerLookupProvider);
    final attached = ref.watch(
      cartControllerProvider.select((c) => c.customer),
    );

    return Padding(
      padding: EdgeInsets.only(bottom: MediaQuery.viewInsetsOf(context).bottom),
      child: Container(
        constraints: BoxConstraints(
          maxHeight: MediaQuery.sizeOf(context).height * 0.9,
        ),
        decoration: const BoxDecoration(
          color: AppColors.surface,
          borderRadius:
              BorderRadius.vertical(top: Radius.circular(AppRadius.xxl)),
        ),
        child: SafeArea(
          top: false,
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              _grabber(),
              _header(attached),
              const Divider(height: 1),
              Flexible(
                child: SingleChildScrollView(
                  padding: const EdgeInsets.all(AppSpacing.xxl),
                  child: LayoutBuilder(
                    builder: (context, constraints) {
                      // Side by side once there is room for both columns.
                      final wide = constraints.maxWidth >= 720;
                      final entry = _entryColumn();
                      final result = _resultColumn(lookup);

                      if (!wide) {
                        return Column(
                          children: [
                            entry,
                            const SizedBox(height: AppSpacing.xl),
                            result,
                          ],
                        );
                      }
                      return Row(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          Expanded(child: entry),
                          const SizedBox(width: AppSpacing.xxl),
                          Expanded(child: result),
                        ],
                      );
                    },
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _grabber() => Container(
        width: 40,
        height: 4,
        margin: const EdgeInsets.symmetric(vertical: AppSpacing.md),
        decoration: BoxDecoration(
          color: AppColors.border,
          borderRadius: AppRadius.brPill,
        ),
      );

  Widget _header(Customer? attached) => Padding(
        padding: const EdgeInsets.fromLTRB(
          AppSpacing.xxl,
          0,
          AppSpacing.md,
          AppSpacing.lg,
        ),
        child: Row(
          children: [
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                children: [
                  Text(
                    attached == null ? 'Add customer' : 'Change customer',
                    overflow: TextOverflow.ellipsis,
                    style: Theme.of(context).textTheme.titleLarge,
                  ),
                  const Text(
                    'Optional — for loyalty points and tier discounts',
                    overflow: TextOverflow.ellipsis,
                    style: TextStyle(
                      fontSize: 12.5,
                      color: AppColors.textSecondary,
                    ),
                  ),
                ],
              ),
            ),
            const SizedBox(width: AppSpacing.sm),
            TextButton(
              onPressed: () => _attachAndClose(null),
              style: TextButton.styleFrom(
                foregroundColor: AppColors.textSecondary,
              ),
              child: const Text('Skip'),
            ),
            IconButton(
              onPressed: () => Navigator.of(context).pop(),
              icon: const Icon(Icons.close_rounded),
              tooltip: 'Close',
            ),
          ],
        ),
      );

  Widget _entryColumn() => Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          _display(),
          const SizedBox(height: AppSpacing.xl),
          Center(
            child: NumericKeypad(
              maxWidth: 340,
              onKey: _append,
              onBackspace: _backspace,
              onClear: _clear,
            ),
          ),
        ],
      );

  Widget _display() => Container(
        height: 68,
        padding: const EdgeInsets.symmetric(horizontal: AppSpacing.lg),
        decoration: BoxDecoration(
          color: AppColors.primarySurface,
          borderRadius: AppRadius.brLg,
          border: Border.all(color: AppColors.primaryBorder),
        ),
        child: Row(
          children: [
            const Text(
              '+91',
              style: TextStyle(
                fontSize: 18,
                fontWeight: FontWeight.w600,
                color: AppColors.textSecondary,
              ),
            ),
            const SizedBox(width: AppSpacing.md),
            // FittedBox guarantees ten digits fit at any sheet width.
            Expanded(
              child: FittedBox(
                fit: BoxFit.scaleDown,
                alignment: Alignment.centerLeft,
                child: Text(
                  _digits.isEmpty
                      ? '– – – – – – – – – –'
                      : _digits.split('').join(' '),
                  style: TextStyle(
                    fontSize: 24,
                    fontWeight: FontWeight.w700,
                    letterSpacing: 1,
                    color: _digits.isEmpty
                        ? AppColors.textTertiary
                        : AppColors.textPrimary,
                  ),
                ),
              ),
            ),
            if (_digits.isNotEmpty)
              IconButton(
                onPressed: _clear,
                icon: const Icon(Icons.close_rounded, size: 20),
                color: AppColors.textTertiary,
                tooltip: 'Clear',
              ),
          ],
        ),
      );

  Widget _resultColumn(CustomerLookupState state) => switch (state) {
        LookupIdle() => _idle(),
        LookupSearching() => const Padding(
            padding: EdgeInsets.symmetric(vertical: AppSpacing.giant),
            child: Center(
              child: CircularProgressIndicator(color: AppColors.primary),
            ),
          ),
        LookupFound(:final customer) => _found(customer),
        LookupNotFound() => _notFound(),
        LookupError(:final message) => _message(
            Icons.error_outline_rounded,
            AppColors.danger,
            message,
          ),
      };

  Widget _idle() {
    final recent = ref.watch(recentCustomersProvider).value ?? const [];

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      mainAxisSize: MainAxisSize.min,
      children: [
        _message(
          Icons.dialpad_rounded,
          AppColors.textTertiary,
          'Key in a 10-digit mobile number. The lookup runs automatically.',
        ),
        if (recent.isNotEmpty) ...[
          const SizedBox(height: AppSpacing.xl),
          const Align(
            alignment: Alignment.centerLeft,
            child: Text(
              'Recent',
              style: TextStyle(
                fontSize: 12.5,
                fontWeight: FontWeight.w600,
                color: AppColors.textSecondary,
              ),
            ),
          ),
          const SizedBox(height: AppSpacing.sm),
          Wrap(
            spacing: AppSpacing.sm,
            runSpacing: AppSpacing.sm,
            children: [
              for (final c in recent.take(4))
                ActionChip(
                  avatar: CircleAvatar(
                    radius: 11,
                    backgroundColor: AppColors.primarySurface,
                    child: Text(
                      Formatters.initials(c.name),
                      style: const TextStyle(
                        fontSize: 9,
                        fontWeight: FontWeight.w700,
                        color: AppColors.primary,
                      ),
                    ),
                  ),
                  label: Text(
                    c.name,
                    overflow: TextOverflow.ellipsis,
                    style: const TextStyle(fontSize: 12.5),
                  ),
                  onPressed: () => _attachAndClose(c),
                ),
            ],
          ),
        ],
      ],
    );
  }

  Widget _found(Customer c) => Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        mainAxisSize: MainAxisSize.min,
        children: [
          Container(
            padding: const EdgeInsets.all(AppSpacing.lg),
            decoration: BoxDecoration(
              color: AppColors.successSurface,
              borderRadius: AppRadius.brLg,
            ),
            child: Column(
              mainAxisSize: MainAxisSize.min,
              children: [
                Row(
                  children: [
                    CircleAvatar(
                      radius: 22,
                      backgroundColor: AppColors.surface,
                      child: Text(
                        Formatters.initials(c.name),
                        style: const TextStyle(
                          color: AppColors.primary,
                          fontSize: 15,
                          fontWeight: FontWeight.w700,
                        ),
                      ),
                    ),
                    const SizedBox(width: AppSpacing.md),
                    Expanded(
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        mainAxisSize: MainAxisSize.min,
                        children: [
                          Text(
                            c.name,
                            overflow: TextOverflow.ellipsis,
                            style: const TextStyle(
                              fontSize: 16,
                              fontWeight: FontWeight.w600,
                            ),
                          ),
                          Text(
                            Formatters.mobile(c.mobile),
                            overflow: TextOverflow.ellipsis,
                            style: const TextStyle(
                              fontSize: 12.5,
                              color: AppColors.textSecondary,
                            ),
                          ),
                        ],
                      ),
                    ),
                    const SizedBox(width: AppSpacing.sm),
                    StatusPill.tier(c.tier, dense: true),
                  ],
                ),
                const SizedBox(height: AppSpacing.md),
                Row(
                  children: [
                    Expanded(
                      child: _miniStat(
                          '${c.loyaltyPoints}', 'points held'),
                    ),
                    Expanded(
                      child: _miniStat(
                        Formatters.money(c.redeemableValue),
                        'redeemable',
                      ),
                    ),
                    if (c.tier.discountRate > 0)
                      Expanded(
                        child: _miniStat(
                          Formatters.percent(c.tier.discountRate),
                          'auto discount',
                        ),
                      ),
                  ],
                ),
              ],
            ),
          ),
          const SizedBox(height: AppSpacing.lg),
          PrimaryButton(
            label: 'Use this customer',
            icon: Icons.check_rounded,
            large: true,
            onPressed: () => _attachAndClose(c),
          ),
        ],
      );

  Widget _notFound() => Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        mainAxisSize: MainAxisSize.min,
        children: [
          _message(
            Icons.person_search_rounded,
            AppColors.warning,
            'Not registered yet. Add a name to save them, or carry on '
            'without.',
          ),
          const SizedBox(height: AppSpacing.lg),
          TextField(
            controller: _name,
            textCapitalization: TextCapitalization.words,
            enabled: !_saving,
            onSubmitted: (_) => _quickRegister(),
            inputFormatters: [LengthLimitingTextInputFormatter(60)],
            decoration: const InputDecoration(
              labelText: 'Customer name',
              hintText: 'Full name',
              prefixIcon: Icon(Icons.person_outline_rounded),
            ),
          ),
          if (_error != null) ...[
            const SizedBox(height: AppSpacing.sm),
            Text(
              _error!,
              style: const TextStyle(color: AppColors.danger, fontSize: 12.5),
            ),
          ],
          const SizedBox(height: AppSpacing.lg),
          PrimaryButton(
            label: 'Save & use',
            icon: Icons.person_add_alt_1_rounded,
            large: true,
            busy: _saving,
            onPressed: _quickRegister,
          ),
          const SizedBox(height: AppSpacing.sm),
          PrimaryButton(
            label: 'Continue without customer',
            tone: ButtonTone.neutral,
            onPressed: _saving ? null : () => _attachAndClose(null),
          ),
        ],
      );

  Widget _miniStat(String value, String label) => Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        mainAxisSize: MainAxisSize.min,
        children: [
          FittedBox(
            fit: BoxFit.scaleDown,
            alignment: Alignment.centerLeft,
            child: Text(
              value,
              style: const TextStyle(
                fontSize: 16,
                fontWeight: FontWeight.w700,
                color: AppColors.success,
              ),
            ),
          ),
          Text(
            label,
            overflow: TextOverflow.ellipsis,
            style: const TextStyle(
              fontSize: 11,
              color: AppColors.textSecondary,
            ),
          ),
        ],
      );

  Widget _message(IconData icon, Color color, String text) => Container(
        padding: const EdgeInsets.all(AppSpacing.lg),
        decoration: BoxDecoration(
          color: AppColors.surfaceAlt,
          borderRadius: AppRadius.brMd,
          border: Border.all(color: AppColors.border),
        ),
        child: Row(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Icon(icon, size: 19, color: color),
            const SizedBox(width: AppSpacing.md),
            Expanded(
              child: Text(
                text,
                style: const TextStyle(
                  fontSize: 13,
                  color: AppColors.textSecondary,
                  height: 1.5,
                ),
              ),
            ),
          ],
        ),
      );
}