import 'dart:typed_data';

import 'package:intl/intl.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

import 'fuel_report.dart';

final _dateFormat = DateFormat.yMMMd();
final _currencyFormat = NumberFormat.simpleCurrency();

/// Renders [report] as a single-page-friendly PDF: a per-vehicle table
/// (VIN, nickname, entry count, gallons, total cost) plus a grand-total
/// row, suitable for attaching to a fuel tax refund submission or handing
/// to a printer.
Future<Uint8List> buildFuelReportPdf(FuelReport report) async {
  final doc = pw.Document();

  doc.addPage(
    pw.MultiPage(
      pageFormat: PdfPageFormat.letter,
      header: (context) => pw.Column(
        crossAxisAlignment: pw.CrossAxisAlignment.start,
        children: [
          pw.Text('Fuel Report', style: pw.TextStyle(fontSize: 20, fontWeight: pw.FontWeight.bold)),
          pw.Text(
            '${_dateFormat.format(report.startDate)} – ${_dateFormat.format(report.endDate)}',
            style: const pw.TextStyle(fontSize: 12, color: PdfColors.grey700),
          ),
          pw.SizedBox(height: 16),
        ],
      ),
      build: (context) => [
        if (report.rows.isEmpty)
          pw.Text('No vehicles had a receipted fuel entry in this date range.')
        else
          pw.TableHelper.fromTextArray(
            headers: ['Vehicle', 'VIN', 'Entries', 'Gallons', 'Total Cost'],
            data: [
              for (final row in report.rows)
                [
                  row.vehicle.nickname?.trim().isNotEmpty == true ? row.vehicle.nickname! : '—',
                  row.vehicle.vin,
                  row.entryCount.toString(),
                  row.totalGallons.toStringAsFixed(3),
                  _currencyFormat.format(row.totalCost),
                ],
            ],
            cellAlignments: const {
              2: pw.Alignment.centerRight,
              3: pw.Alignment.centerRight,
              4: pw.Alignment.centerRight,
            },
            headerAlignments: const {
              2: pw.Alignment.centerRight,
              3: pw.Alignment.centerRight,
              4: pw.Alignment.centerRight,
            },
            headerStyle: pw.TextStyle(fontWeight: pw.FontWeight.bold),
            cellPadding: const pw.EdgeInsets.symmetric(horizontal: 8, vertical: 6),
          ),
        pw.SizedBox(height: 12),
        pw.Divider(),
        pw.Row(
          mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
          children: [
            pw.Text('Total', style: pw.TextStyle(fontWeight: pw.FontWeight.bold)),
            pw.Text(
              '${report.totalGallons.toStringAsFixed(3)} gal · ${_currencyFormat.format(report.totalCost)}',
              style: pw.TextStyle(fontWeight: pw.FontWeight.bold),
            ),
          ],
        ),
      ],
    ),
  );

  return doc.save();
}

/// `fuel-report-<start>-<end>.pdf`, e.g. `fuel-report-20260101-20260331.pdf`.
String fuelReportFileName(FuelReport report) {
  final fmt = DateFormat('yyyyMMdd');
  return 'fuel-report-${fmt.format(report.startDate)}-${fmt.format(report.endDate)}.pdf';
}