import 'package:flutter/material.dart';

import '../../../core/constants/app_constants.dart';
import '../../../core/theme/app_colors.dart';
import '../../../core/theme/app_dimens.dart';
import '../../../core/theme/app_typography.dart';
import '../../../core/utils/formatters.dart';
import '../../../domain/entities/transaction.dart';

/// Paper-like preview of what the thermal printer produced.
class ReceiptPreview extends StatelessWidget {
  const ReceiptPreview({super.key, required this.transaction});

  final SaleTransaction transaction;

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

    return Container(
      decoration: BoxDecoration(
        color: AppColors.surface,
        borderRadius: AppRadius.brLg,
        boxShadow: AppColors.shadowMd,
      ),
      child: Column(children: [
        const _Perforation(top: true),
        Expanded(
          child: SingleChildScrollView(
            padding: const EdgeInsets.symmetric(
              horizontal: AppSpacing.xxl,
              vertical: AppSpacing.xl,
            ),
            child: DefaultTextStyle(
              style: AppTypography.mono(11.5, color: AppColors.textPrimary),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  Center(
                    child: Column(children: [
                      Text(
                        AppConstants.storeName.toUpperCase(),
                        style: AppTypography.mono(15)
                            .copyWith(fontWeight: FontWeight.w700),
                      ),
                      const SizedBox(height: 3),
                      Text(AppConstants.storeAddress,
                          textAlign: TextAlign.center,
                          style: AppTypography.mono(9.5)),
                      Text('GSTIN: ${AppConstants.storeGstin}',
                          style: AppTypography.mono(9.5)),
                      const SizedBox(height: AppSpacing.sm),
                      Text('TAX INVOICE',
                          style: AppTypography.mono(11.5)
                              .copyWith(fontWeight: FontWeight.w700)),
                    ]),
                  ),

                  const _Dashes(),
                  _row('Invoice', txn.invoiceNumber),
                  _row('Date', Formatters.receiptStamp(txn.createdAt)),
                  _row('Cashier', txn.cashierName),
                  _row('Customer', txn.customer?.name ?? 'Walk-in'),

                  const _Dashes(),
                  Row(children: [
                    Expanded(flex: 5, child: _bold('Item')),
                    Expanded(
                      flex: 2,
                      child: _bold('Qty', align: TextAlign.center),
                    ),
                    Expanded(
                      flex: 3,
                      child: _bold('Amount', align: TextAlign.right),
                    ),
                  ]),
                  const SizedBox(height: AppSpacing.xs),

                  ...cart.lines.map((line) => Padding(
                        padding: const EdgeInsets.symmetric(vertical: 2.5),
                        child: Row(children: [
                          Expanded(flex: 5, child: Text(line.product.name)),
                          Expanded(
                            flex: 2,
                            child: Text(
                              line.quantity % 1 == 0
                                  ? line.quantity.toStringAsFixed(0)
                                  : line.quantity.toStringAsFixed(2),
                              textAlign: TextAlign.center,
                            ),
                          ),
                          Expanded(
                            flex: 3,
                            child: Text(
                              line.payable.toStringAsFixed(2),
                              textAlign: TextAlign.right,
                            ),
                          ),
                        ]),
                      )),

                  const _Dashes(),
                  _row('Subtotal', cart.subtotal.toStringAsFixed(2)),
                  if (cart.billDiscountTotal > 0)
                    _row('Discount',
                        '-${cart.billDiscountTotal.toStringAsFixed(2)}'),
                  if (cart.loyaltyRedemptionValue > 0)
                    _row('Points redeemed',
                        '-${cart.loyaltyRedemptionValue.toStringAsFixed(2)}'),
                  _row('CGST', cart.cgst.toStringAsFixed(2)),
                  _row('SGST', cart.sgst.toStringAsFixed(2)),
                  if (cart.roundOff != 0)
                    _row('Round off', cart.roundOff.toStringAsFixed(2)),

                  const _Dashes(),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
                    children: [
                      Text('TOTAL',
                          style: AppTypography.mono(15).copyWith(
                            fontWeight: FontWeight.w800,
                            color: AppColors.textPrimary,
                          )),
                      Text(
                        Formatters.money(txn.total),
                        style: AppTypography.mono(15).copyWith(
                          fontWeight: FontWeight.w800,
                          color: AppColors.textPrimary,
                        ),
                      ),
                    ],
                  ),

                  const _Dashes(),
                  ...txn.payments.map((p) =>
                      _row(p.method.label, p.amount.toStringAsFixed(2))),
                  if (txn.changeDue > 0)
                    _row('Change', txn.changeDue.toStringAsFixed(2)),

                  if (txn.customer != null) ...[
                    const _Dashes(),
                    _row('Points earned', '+${txn.pointsEarned}'),
                    _row('Membership', txn.customer!.tier.label),
                  ],

                  const SizedBox(height: AppSpacing.lg),
                  Center(
                    child: Column(children: [
                      _FakeBarcode(value: txn.invoiceNumber),
                      const SizedBox(height: AppSpacing.sm),
                      Text('Thank you for shopping with us!',
                          style: AppTypography.mono(11)
                              .copyWith(fontWeight: FontWeight.w700)),
                      const SizedBox(height: 2),
                      Text('Powered by Nearle POS',
                          style: AppTypography.mono(9)),
                    ]),
                  ),
                ],
              ),
            ),
          ),
        ),
        const _Perforation(top: false),
      ]),
    );
  }

  Widget _row(String label, String value) => Padding(
        padding: const EdgeInsets.symmetric(vertical: 1.5),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: [Text(label), Text(value)],
        ),
      );

  Widget _bold(String text, {TextAlign align = TextAlign.left}) => Text(
        text,
        textAlign: align,
        style: AppTypography.mono(11.5).copyWith(
          fontWeight: FontWeight.w700,
          color: AppColors.textPrimary,
        ),
      );
}

class _Dashes extends StatelessWidget {
  const _Dashes();

  @override
  Widget build(BuildContext context) {
    return const Padding(
      padding: EdgeInsets.symmetric(vertical: AppSpacing.sm),
      child: Text(
        '- - - - - - - - - - - - - - - - - - - - - - - - - -',
        maxLines: 1,
        overflow: TextOverflow.clip,
        style: TextStyle(color: AppColors.textTertiary, fontSize: 10),
      ),
    );
  }
}

/// Zig-zag torn-paper edge.
class _Perforation extends StatelessWidget {
  const _Perforation({required this.top});

  final bool top;

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 10,
      child: CustomPaint(
        size: const Size(double.infinity, 10),
        painter: _PerforationPainter(top: top),
      ),
    );
  }
}

class _PerforationPainter extends CustomPainter {
  const _PerforationPainter({required this.top});

  final bool top;

  @override
  void paint(Canvas canvas, Size size) {
    const tooth = 12.0;
    final path = Path();

    if (top) {
      path.moveTo(0, size.height);
      for (var x = 0.0; x < size.width; x += tooth) {
        path.lineTo(x + tooth / 2, 0);
        path.lineTo(x + tooth, size.height);
      }
      path.lineTo(size.width, size.height);
    } else {
      path.moveTo(0, 0);
      for (var x = 0.0; x < size.width; x += tooth) {
        path.lineTo(x + tooth / 2, size.height);
        path.lineTo(x + tooth, 0);
      }
      path.lineTo(size.width, 0);
    }
    path.close();

    canvas.drawPath(path, Paint()..color = AppColors.surface);
  }

  @override
  bool shouldRepaint(covariant _PerforationPainter oldDelegate) =>
      oldDelegate.top != top;
}

/// Decorative Code-128-style bar rendering for the preview only.
class _FakeBarcode extends StatelessWidget {
  const _FakeBarcode({required this.value});

  final String value;

  @override
  Widget build(BuildContext context) {
    final bars = value.codeUnits;

    return Column(children: [
      SizedBox(
        height: 38,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            for (var i = 0; i < bars.length * 2; i++)
              Container(
                width: (bars[i ~/ 2] % 3 == 0) ? 3 : 1.5,
                margin: const EdgeInsets.symmetric(horizontal: 0.7),
                color: i.isEven
                    ? AppColors.textPrimary
                    : Colors.transparent,
              ),
          ],
        ),
      ),
      const SizedBox(height: 3),
      Text(value, style: AppTypography.mono(9)),
    ]);
  }
}