import 'dart:async';

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

import '../../../core/router/app_router.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/theme/app_layout.dart';
import '../../../core/theme/app_typography.dart';
import '../../../core/utils/extensions.dart';
import '../../../core/utils/formatters.dart';
import '../../../core/widgets/empty_state.dart';
import '../../../core/widgets/primary_button.dart';
import '../../../domain/entities/cart.dart';
import '../../customer/widgets/customer_capture_sheet.dart';
import '../providers/cart_controller.dart';
import 'admin_pin_dialog.dart';
import 'cart_line_tile.dart';
import 'discount_sheet.dart';

/// Always-visible bill on the right of the dashboard.
class BillingPanel extends ConsumerWidget {
  const BillingPanel({super.key, this.inSheet = false});

  final bool inSheet;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final cart = ref.watch(cartControllerProvider);
    final controller = ref.read(cartControllerProvider.notifier);

    return Container(
      color: AppColors.surface,
      child: Column(children: [
        _Header(cart: cart, inSheet: inSheet),
        const Divider(height: 1),
        Expanded(
          child: cart.isEmpty
              ? const EmptyState(
                  title: 'Cart is empty',
                  message: 'Scan a barcode or tap a product to begin.',
                  emoji: '🛒',
                  compact: true,
                )
              : ListView.separated(
                  padding: const EdgeInsets.symmetric(
                    horizontal: AppSpacing.lg,
                    vertical: AppSpacing.md,
                  ),
                  itemCount: cart.lines.length,
                  separatorBuilder: (_, __) =>
                      const SizedBox(height: AppSpacing.sm),
                  itemBuilder: (_, i) {
                    // Newest line first mirrors what the cashier just scanned.
                    final line = cart.lines[cart.lines.length - 1 - i];
                    return CartLineTile(
                      key: ValueKey(line.product.id),
                      line: line,
                      onIncrement: () => controller.increment(line.product.id),
                      onDecrement: () => controller.decrement(line.product.id),
                      onRemove: () => _removeLine(
                        context,
                        ref,
                        controller,
                        line.product.id,
                      ),
                      onDiscount: () =>
                          showLineDiscountSheet(context, ref, line),
                    );
                  },
                ),
        ),
        if (cart.isNotEmpty) _Summary(cart: cart),
        _Actions(cart: cart),
      ],),
    );
  }
}

/// Once an item is on the bill, taking it back off needs an admin's
/// approval — a cashier can always start an entirely new sale instead. This
/// is the one gate both removal paths (a single line, or the whole cart) go
/// through, so they can never drift out of sync with each other.
Future<void> _removeLine(
  BuildContext context,
  WidgetRef ref,
  CartController controller,
  String productId,
) async {
  final ok = await requireAdminPin(
    context,
    ref,
    reason: 'Removing a scanned item from the bill needs admin approval.',
  );
  if (ok) controller.removeLine(productId);
}

Future<void> _clearCart(
  BuildContext context,
  WidgetRef ref,
  CartController controller,
) async {
  final ok = await requireAdminPin(
    context,
    ref,
    reason: 'Clearing the whole bill needs admin approval.',
  );
  if (ok) controller.clear();
}

class _Header extends ConsumerWidget {
  const _Header({required this.cart, required this.inSheet});

  final Cart cart;
  final bool inSheet;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final controller = ref.read(cartControllerProvider.notifier);
    // Same fixed height as the page header on the left, so the two bars
    // line up on one visual line instead of the cart title floating lower.
    final contentPadding = PosLayout.of(context).contentPadding;

    return Container(
      constraints: const BoxConstraints(minHeight: AppSizes.headerHeight),
      padding: EdgeInsets.symmetric(horizontal: contentPadding),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Flexible(
            child: Text(
              'Cart',
              overflow: TextOverflow.ellipsis,
              style: context.text.titleLarge,
            ),
          ),
          if (cart.isNotEmpty) ...[

            Container(
              padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 2),
              decoration: const BoxDecoration(
                color: AppColors.primarySurface,
                borderRadius: AppRadius.brPill,
              ),
              child: Text(
                '${cart.lineCount}',
                style: const TextStyle(
                  color: AppColors.primary,
                  fontWeight: FontWeight.w700,
                  fontSize: 12.5,
                ),
              ),
            ),
          ],
          SizedBox(),
          SizedBox(),

          Spacer(),


          // Icon-only actions: labelled buttons overflowed the 380px panel.
          // Grouped tight with even spacing, flush against the same right
          // edge the header buttons on the left use.
          Row(
            mainAxisSize: MainAxisSize.min,
            children: [
              if (controller.canUndo)
                _IconAction(
                  icon: Icons.undo_rounded,
                  tooltip: 'Undo (F8)',
                  color: AppColors.textSecondary,
                  onTap: controller.undo,
                ),
              if (cart.isNotEmpty) ...[
                _IconAction(
                  icon: Icons.pause_circle_outline_rounded,
                  tooltip: 'Park bill',
                  color: AppColors.warning,
                  onTap: () async {
                    await controller.park();
                    ref.invalidate(parkedBillsProvider);
                    if (context.mounted) context.showSnack('Bill parked');
                  },
                ),
                _IconAction(
                  icon: Icons.delete_outline_rounded,
                  tooltip: 'Clear bill',
                  color: AppColors.danger,
                  onTap: () => _clearCart(context, ref, controller),
                ),
              ],
              if (inSheet)
                _IconAction(
                  icon: Icons.close_rounded,
                  tooltip: 'Close',
                  color: AppColors.textSecondary,
                  onTap: () => Navigator.of(context).pop(),
                ),
            ],
          ),
        ],
      ),
    );
  }
}

/// Compact square action used in the bill header.
class _IconAction extends StatelessWidget {
  const _IconAction({
    required this.icon,
    required this.tooltip,
    required this.color,
    required this.onTap,
  });

  final IconData icon;
  final String tooltip;
  final Color color;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    return Tooltip(
      message: tooltip,
      child: IconButton(
        onPressed: onTap,
        icon: Icon(icon, size: 19),
        color: color,
        visualDensity: VisualDensity.compact,
        constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
        padding: EdgeInsets.zero,
      ),
    );
  }
}

class _Summary extends ConsumerWidget {
  const _Summary({required this.cart});

  final Cart cart;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final controller = ref.read(cartControllerProvider.notifier);

    return Container(
      padding: const EdgeInsets.fromLTRB(
        AppSpacing.xl,
        AppSpacing.lg,
        AppSpacing.xl,
        AppSpacing.md,
      ),
      decoration: const BoxDecoration(
        border: Border(top: BorderSide(color: AppColors.divider)),
      ),
      child: Column(children: [
        if (cart.pointsEarned > 0)
          Container(
            width: double.infinity,
            margin: const EdgeInsets.only(bottom: AppSpacing.md),
            padding: const EdgeInsets.symmetric(
              horizontal: AppSpacing.md,
              vertical: AppSpacing.sm + 2,
            ),
            decoration: const BoxDecoration(
              color: AppColors.successSurface,
              borderRadius: AppRadius.brSm,
            ),
            child: Row(children: [
              const Icon(Icons.stars_rounded,
                  size: 16, color: AppColors.success,),
              const SizedBox(width: AppSpacing.sm),
              Text(
                'This sale earns +${cart.pointsEarned} pts',
                style: const TextStyle(
                  color: AppColors.success,
                  fontWeight: FontWeight.w700,
                  fontSize: 13,
                ),
              ),
            ],),
          ),

        _Row(label: 'Subtotal', value: Formatters.money(cart.subtotal)),

        if (cart.membershipDiscountAmount > 0)
          _Row(
            label: '${cart.customer!.tier.label} discount',
            value: '-${Formatters.money(cart.membershipDiscountAmount)}',
            valueColor: AppColors.success,
          ),

        // Named individually rather than lumped into one "Promotions" line:
        // a shopper who came in for a specific offer needs to see it applied,
        // and a cashier being asked "did the weekend deal come off?" needs to
        // answer without opening a report.
        for (final applied in cart.appliedPromos)
          _Row(
            label: applied.promo.name,
            value: '-${Formatters.money(applied.amount)}',
            valueColor: AppColors.success,
          ),

        _Row(
          label: 'GST',
          value: Formatters.money(cart.taxAmount),
          hint: cart.taxBreakdown.keys.isEmpty
              ? null
              : cart.taxBreakdown.keys
                  .map((r) => '${(r * 100).toStringAsFixed(0)}%')
                  .join(', '),
        ),

        InkWell(
          onTap: () => showBillDiscountSheet(context, ref),
          borderRadius: AppRadius.brXs,
          child: _Row(
            label: 'Discount',
            value: cart.manualBillDiscountAmount > 0
                ? '-${Formatters.money(cart.manualBillDiscountAmount)}'
                : '-${Formatters.money(0)}',
            valueColor: cart.manualBillDiscountAmount > 0
                ? AppColors.success
                : null,
            trailingIcon: Icons.edit_outlined,
          ),
        ),

        if (cart.maxRedeemablePoints > 0 || cart.pointsRedeemed > 0)
          InkWell(
            onTap: () => cart.pointsRedeemed > 0
                ? controller.clearRedemption()
                : controller.redeemAllPoints(),
            borderRadius: AppRadius.brXs,
            child: _Row(
              label: cart.pointsRedeemed > 0
                  ? 'Points redeemed (${cart.pointsRedeemed})'
                  : 'Redeem ${cart.maxRedeemablePoints} points',
              value: cart.pointsRedeemed > 0
                  ? '-${Formatters.money(cart.loyaltyRedemptionValue)}'
                  : 'Apply',
              valueColor: AppColors.primary,
              trailingIcon: cart.pointsRedeemed > 0
                  ? Icons.close_rounded
                  : Icons.add_rounded,
            ),
          ),

        if (cart.roundOff != 0)
          _Row(
            label: 'Round Off',
            value: '${cart.roundOff >= 0 ? '+' : ''}'
                '${Formatters.money(cart.roundOff)}',
          ),

        const Padding(
          padding: EdgeInsets.symmetric(vertical: AppSpacing.md),
          child: Divider(height: 1),
        ),

        Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Text('Total', style: context.text.titleLarge),
            Text(
              Formatters.money(cart.grandTotal),
              style: AppTypography.money(26, color: AppColors.primary),
            ),
          ],
        ),

        if (cart.totalSavings > 0)
          Padding(
            padding: const EdgeInsets.only(top: AppSpacing.xs),
            child: Align(
              alignment: Alignment.centerRight,
              child: Text(
                'You saved ${Formatters.money(cart.totalSavings)}',
                style: const TextStyle(
                  color: AppColors.success,
                  fontSize: 12,
                  fontWeight: FontWeight.w600,
                ),
              ),
            ),
          ),
      ],),
    );
  }
}

class _Row extends StatelessWidget {
  const _Row({
    required this.label,
    required this.value,
    this.valueColor,
    this.hint,
    this.trailingIcon,
  });

  final String label;
  final String value;
  final Color? valueColor;
  final String? hint;
  final IconData? trailingIcon;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: AppSpacing.xs + 2),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
        Flexible(
          child: Text(
            label,
            overflow: TextOverflow.ellipsis,
            style: const TextStyle(
              fontSize: 14,
              color: AppColors.textSecondary,
            ),
          ),
        ),
        if (hint != null) ...[
          const SizedBox(width: AppSpacing.xs),
          Text('($hint)',
              style: const TextStyle(
                fontSize: 11.5,
                color: AppColors.textTertiary,
              ),),
        ],
        const SizedBox(width: AppSpacing.sm),
        const Spacer(),
        Text(
          value,
          style: AppTypography.money(
            14.5,
            weight: FontWeight.w600,
            color: valueColor ?? AppColors.textPrimary,
          ),
        ),
        if (trailingIcon != null) ...[

          Icon(trailingIcon, size: 14, color: AppColors.textTertiary),
        ],
      ],),
    );
  }
}

class _Actions extends ConsumerWidget {
  const _Actions({required this.cart});

  final Cart cart;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final enabled = cart.isNotEmpty;

    return Container(
      padding: const EdgeInsets.fromLTRB(
        AppSpacing.xl,
        AppSpacing.sm,
        AppSpacing.xl,
        AppSpacing.xl,
      ),
      child: PrimaryButton(
        label: 'CHARGE',
        large: true,
        onPressed: enabled
            ? () async {
                // Ask once per bill, before payment. Skipping is one tap and
                // leaves the sale as walk-in.
                if (ref.read(cartControllerProvider).customer == null) {
                  await showCustomerCaptureSheet(context);
                }
                // Navigation result is not needed here.
                if (context.mounted) unawaited(context.push(AppRoutes.payment));
              }
            : null,
        trailing: enabled
            ? Text(
                Formatters.money(cart.grandTotal),
                style: AppTypography.money(21, color: Colors.white),
              )
            : null,
      ),
    );
  }
}