import 'dart:async';

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

import '../../../app/providers.dart';
import '../../../core/constants/app_constants.dart';
import '../../../core/router/app_router.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/theme/app_typography.dart';
import '../../../core/utils/extensions.dart';
import '../../../core/utils/formatters.dart';
import '../../../core/widgets/glass_card.dart';
import '../../../core/widgets/primary_button.dart';
import '../../../data/sync/sync_engine.dart';
import '../../../domain/entities/transaction.dart';
import '../../modules/providers/printer_settings.dart';
import '../../pos/providers/cart_controller.dart';
import '../../pos/providers/catalog_providers.dart';
import '../../sync/providers/sync_controller.dart';
import '../widgets/receipt_preview.dart';

/// Confirmation screen.
///
/// The bill is written to SQLite the instant checkout completes, but is
/// deliberately held back from the server for [AppConstants.postSaleResetDelay]
/// — long enough to catch a mistake. Counts down and starts the next sale (and
/// releases the bill to the sync engine) on its own so an unattended terminal
/// never sits on a finished bill forever; "Cancel sale" inside the window
/// voids it instead and hands the cart straight back.
class ReceiptScreen extends ConsumerStatefulWidget {
  const ReceiptScreen({super.key, required this.transaction});

  final SaleTransaction transaction;

  @override
  ConsumerState<ReceiptScreen> createState() => _ReceiptScreenState();
}

class _ReceiptScreenState extends ConsumerState<ReceiptScreen> {
  late int _seconds = AppConstants.postSaleResetDelay.inSeconds;
  Timer? _timer;

  /// True while a cancellation is being written to disk — guards against a
  /// second tap voiding a sale that is already half-reversed.
  bool _voiding = false;

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

    // Auto-print is opt-in and only fires when a printer was actually
    // selected, so it can never fail invisibly on a terminal with none.
    WidgetsBinding.instance.addPostFrameCallback((_) async {
      final settings = ref.read(printerSettingsProvider);
      if (!settings.autoPrint || !settings.hasPrinter) return;

      final ok = await ref.read(receiptServiceProvider).printDirect(
            widget.transaction,
            printerUrl: settings.printerUrl,
          );
      if (!ok && mounted) {
        _cancelAutoReturn();
        ScaffoldMessenger.of(context)
          ..hideCurrentSnackBar()
          ..showSnackBar(const SnackBar(
            backgroundColor: AppColors.danger,
            content: Text(
              'Printer did not respond — use Print to send it again.',
            ),
          ),);
      }
    });

    _timer = Timer.periodic(const Duration(seconds: 1), (t) {
      if (!mounted) return;
      setState(() => _seconds--);
      if (_seconds <= 0) _newSale();
    });
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }

  void _cancelAutoReturn() {
    _timer?.cancel();
    if (mounted) setState(() => _seconds = -1);
  }

  void _newSale() {
    _timer?.cancel();
    // This is the one moment the bill is actually released to the server —
    // whether the window ran out on its own or New Sale was pressed early,
    // the cashier has let this bill stand.
    ref.read(syncEngineProvider).nudge(SyncTrigger.saleCommitted);
    ref.read(cartControllerProvider.notifier).reset();
    if (mounted) context.go(AppRoutes.pos);
  }

  /// Undoes the sale: deletes the order, puts the stock back, restores an
  /// attached shopper's loyalty balance, and hands the exact same cart back
  /// to the billing screen. Never touches the sync engine — this bill must
  /// never reach the server.
  Future<void> _cancelSale() async {
    if (_voiding) return;
    setState(() => _voiding = true);
    _timer?.cancel();

    final txn = widget.transaction;
    await ref.read(transactionRepositoryProvider).voidSale(
          transaction: txn,
          stockMovements: {
            for (final line in txn.cart.lines) line.product.id: line.quantity,
          },
        );

    ref.invalidate(allProductsProvider);
    ref.invalidate(visibleProductsProvider);
    ref.read(orderVersionProvider.notifier).state++;
    ref.read(cartControllerProvider.notifier).restore(txn.cart);

    if (mounted) context.go(AppRoutes.pos);
  }

  @override
  Widget build(BuildContext context) {
    final txn = widget.transaction;

    return Scaffold(
      backgroundColor: AppColors.background,
      body: SafeArea(
        child: Listener(
          onPointerDown: (_) => _cancelAutoReturn(),
          child: Padding(
            padding: const EdgeInsets.all(AppSpacing.xxl),
            child: context.isCompact
                ? SingleChildScrollView(
                    child: Column(children: [
                      _summary(txn),
                      const SizedBox(height: AppSpacing.lg),
                      SizedBox(
                        height: 480,
                        child: ReceiptPreview(transaction: txn),
                      ),
                    ],),
                  )
                : Row(
                    crossAxisAlignment: CrossAxisAlignment.stretch,
                    children: [
                      Expanded(flex: 5, child: _summary(txn)),
                      const SizedBox(width: AppSpacing.xxl),
                      Expanded(
                        flex: 4,
                        child: ReceiptPreview(transaction: txn),
                      ),
                    ],
                  ),
          ),
        ),
      ),
    );
  }

  Widget _summary(SaleTransaction txn) {
    return GlassCard(
      padding: const EdgeInsets.all(AppSpacing.xxxl),
      radius: AppRadius.xxl,
      shadows: AppColors.shadowMd,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Center(
            child: Container(
              width: 84,
              height: 84,
              decoration: const BoxDecoration(
                color: AppColors.successSurface,
                shape: BoxShape.circle,
              ),
              child: const Icon(Icons.check_rounded,
                  size: 44, color: AppColors.success,),
            )
                .animate()
                .scale(
                  duration: 340.ms,
                  curve: Curves.easeOutBack,
                  begin: const Offset(0.5, 0.5),
                )
                .fadeIn(),
          ),
          const SizedBox(height: AppSpacing.xl),
          Text('Sale complete',
              textAlign: TextAlign.center,
              style: context.text.headlineMedium,),
          const SizedBox(height: AppSpacing.xs),
          Text(
            '${txn.invoiceNumber}  ·  ${Formatters.dateTime(txn.createdAt)}',
            textAlign: TextAlign.center,
            style: context.text.bodySmall,
          ),

          const SizedBox(height: AppSpacing.xxl),
          Container(
            padding: const EdgeInsets.all(AppSpacing.xl),
            decoration: const BoxDecoration(
              color: AppColors.primarySurface,
              borderRadius: AppRadius.brLg,
            ),
            child: Column(children: [
              Text('Amount paid', style: context.text.labelMedium),
              Text(
                Formatters.money(txn.total),
                style: AppTypography.money(36, color: AppColors.primary),
              ),
              const SizedBox(height: AppSpacing.md),
              const Divider(),
              const SizedBox(height: AppSpacing.md),
              _row('Paid via', txn.paymentSummary),
              if (txn.changeDue > 0)
                _row('Change returned', Formatters.money(txn.changeDue),
                    highlight: AppColors.success,),
              _row('Items', '${txn.cart.lineCount}'),
              if (txn.customer != null) ...[
                _row('Customer', txn.customer!.name),
                _row('Points earned', '+${txn.pointsEarned}',
                    highlight: AppColors.success,),
                if (txn.pointsRedeemed > 0)
                  _row('Points redeemed', '-${txn.pointsRedeemed}'),
              ],
              if (txn.cart.totalSavings > 0)
                _row(
                  'Customer saved',
                  Formatters.money(txn.cart.totalSavings),
                  highlight: AppColors.success,
                ),
            ],),
          ),

          const SizedBox(height: AppSpacing.xxl),
          // Wrap, so three actions never overflow a narrow terminal.
          Wrap(
            spacing: AppSpacing.md,
            runSpacing: AppSpacing.md,
            children: [
              SizedBox(
                width: 150,
                child: PrimaryButton(
                  label: 'Print',
                  icon: Icons.print_outlined,
                  tone: ButtonTone.neutral,
                  onPressed: () async {
                    _cancelAutoReturn();
                    final settings = ref.read(printerSettingsProvider);
                    final service = ref.read(receiptServiceProvider);

                    // Straight to the roll when one is configured; otherwise
                    // the system preview, which works with no hardware.
                    final printed = settings.hasPrinter &&
                        await service.printDirect(
                          txn,
                          printerUrl: settings.printerUrl,
                        );
                    if (!printed) await service.printPreview(txn);
                  },
                ),
              ),
              SizedBox(
                width: 170,
                child: PrimaryButton(
                  label: 'WhatsApp',
                  icon: Icons.chat_rounded,
                  tone: txn.customer == null
                      ? ButtonTone.neutral
                      : ButtonTone.ghost,
                  onPressed: txn.customer == null
                      ? null
                      : () async {
                          _cancelAutoReturn();
                          final sent = await ref
                              .read(receiptServiceProvider)
                              .sendToWhatsApp(txn);
                          if (!mounted || sent) return;
                          ScaffoldMessenger.of(context)
                            ..hideCurrentSnackBar()
                            ..showSnackBar(const SnackBar(
                              content: Text(
                                'Could not open WhatsApp on this device.',
                              ),
                            ),);
                        },
                ),
              ),
              SizedBox(
                width: 170,
                child: PrimaryButton(
                  label: 'Share PDF',
                  icon: Icons.ios_share_rounded,
                  tone: ButtonTone.neutral,
                  onPressed: () {
                    _cancelAutoReturn();
                    ref.read(receiptServiceProvider).sharePdf(txn);
                  },
                ),
              ),
            ],
          ),
          if (txn.customer == null)
            const Padding(
              padding: EdgeInsets.only(top: AppSpacing.sm),
              child: Text(
                'No mobile number captured, so WhatsApp is unavailable for '
                'this bill.',
                style: TextStyle(
                  fontSize: 12,
                  color: AppColors.textTertiary,
                ),
              ),
            ),
          const SizedBox(height: AppSpacing.md),
          PrimaryButton(
            label: _seconds > 0
                ? 'New Sale  ($_seconds)'
                : 'New Sale',
            icon: Icons.add_shopping_cart_rounded,
            large: true,
            onPressed: _voiding ? null : _newSale,
          ),
          const SizedBox(height: AppSpacing.sm),
          TextButton.icon(
            onPressed: _voiding ? null : _cancelSale,
            icon: _voiding
                ? const SizedBox(
                    width: 14,
                    height: 14,
                    child: CircularProgressIndicator(
                      strokeWidth: 2,
                      color: AppColors.danger,
                    ),
                  )
                : const Icon(Icons.undo_rounded, size: 16),
            label: Text(_voiding ? 'Cancelling…' : 'Cancel sale'),
            style: TextButton.styleFrom(foregroundColor: AppColors.danger),
          ),
        ],
      ),
    );
  }

  Widget _row(String label, String value, {Color? highlight}) => Padding(
        padding: const EdgeInsets.symmetric(vertical: AppSpacing.xs),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [
            Text(label,
                style: const TextStyle(
                  fontSize: 13.5,
                  color: AppColors.textSecondary,
                ),),
            Text(
              value,
              style: TextStyle(
                fontSize: 13.5,
                fontWeight: FontWeight.w700,
                color: highlight ?? AppColors.textPrimary,
              ),
            ),
          ],
        ),
      );
}