import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:printing/printing.dart';
import 'package:provider/provider.dart';
import 'package:url_launcher/url_launcher.dart';

import '../services/app_state.dart';
import '../services/fuel_report.dart';
import '../services/fuel_report_images.dart';
import '../services/fuel_report_pdf.dart';

/// Missouri's Motor Fuel Refund Claim form isn't something this app can
/// file for the user — it's a state form, submitted to the state — so the
/// Reports tab just links out to where to get it rather than trying to
/// reproduce or embed it.
final _refundFormUrl = Uri.parse(
  'https://dor.mo.gov/forms/?formName=Motor+Fuel+Refund+Claim&category=&year=99',
);

class ReportScreen extends StatefulWidget {
  const ReportScreen({super.key});

  @override
  State<ReportScreen> createState() => _ReportScreenState();
}

class _ReportScreenState extends State<ReportScreen> with AutomaticKeepAliveClientMixin {
  static final _dateFormat = DateFormat.yMMMd();

  DateTime? _startDate;
  DateTime? _endDate;
  bool _includeReceiptImages = false;
  bool _includeLineItems = false;
  bool _busy = false;

  /// Which vehicles (by id) to include in the report — checkboxes next to
  /// each vehicle below the date range. [_seenVehicleIds] tracks every
  /// vehicle a checkbox has ever been shown for, so a vehicle newly
  /// appearing in range (first time it's seen) defaults to selected without
  /// clobbering a selection the user already made for one seen before (e.g.
  /// after picking a different range and back).
  final Set<String> _selectedVehicleIds = {};
  final Set<String> _seenVehicleIds = {};

  // Keeps this tab's state (chosen date range, include-image/line-item
  // toggles) alive when MainShell's PageView builds/tears down tabs
  // outside its cache extent as the user swipes between them.
  @override
  bool get wantKeepAlive => true;

  Future<void> _pickDate({required bool isStart}) async {
    final now = DateTime.now();
    final picked = await showDatePicker(
      context: context,
      initialDate: (isStart ? _startDate : _endDate) ?? now,
      firstDate: DateTime(2000),
      lastDate: now,
    );
    if (picked == null) return;
    setState(() {
      if (isStart) {
        _startDate = picked;
      } else {
        _endDate = picked;
      }
    });
  }

  Future<Uint8List> _buildPdfBytes(FuelReport report) async {
    var receiptImages = const <String, Uint8List>{};
    if (_includeReceiptImages) {
      final loaded = await loadReceiptImageBytes(
        report: report,
        activeProvider: context.read<AppState>().activeProvider,
      );
      receiptImages = loaded.bytesByEntryId;
      if (loaded.failedEntries.isNotEmpty && mounted) {
        final count = loaded.failedEntries.length;
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(
              "$count receipt photo${count == 1 ? '' : 's'} couldn't be included — offline, "
              'not signed in to the provider that has it, or the remote file is gone.',
            ),
            duration: const Duration(seconds: 6),
          ),
        );
      }
    }
    return buildFuelReportPdf(
      report,
      includeLineItems: _includeLineItems,
      includeReceiptImages: _includeReceiptImages,
      receiptImages: receiptImages,
    );
  }

  Future<void> _share(FuelReport report) async {
    setState(() => _busy = true);
    try {
      final bytes = await _buildPdfBytes(report);
      await Printing.sharePdf(bytes: bytes, filename: fuelReportFileName(report));
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _print(FuelReport report) async {
    setState(() => _busy = true);
    try {
      final bytes = await _buildPdfBytes(report);
      await Printing.layoutPdf(onLayout: (_) async => bytes, name: fuelReportFileName(report));
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  Future<void> _openRefundFormLink() async {
    final launched = await launchUrl(_refundFormUrl, mode: LaunchMode.externalApplication);
    if (!launched && mounted) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text("Couldn't open the link.")),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    super.build(context);
    final appState = context.watch<AppState>();

    String? rangeError;
    FuelReport? rawReport;
    if (_startDate != null && _endDate != null) {
      if (_endDate!.isBefore(_startDate!)) {
        rangeError = 'End date must be on or after the start date.';
      } else {
        rawReport = buildFuelReport(
          vehicles: appState.vehicles,
          fuelEntries: appState.fuelEntries,
          startDate: _startDate!,
          endDate: _endDate!,
        );
        for (final row in rawReport.rows) {
          if (_seenVehicleIds.add(row.vehicle.id)) {
            _selectedVehicleIds.add(row.vehicle.id);
          }
        }
      }
    }

    final report = rawReport == null
        ? null
        : FuelReport(
            startDate: rawReport.startDate,
            endDate: rawReport.endDate,
            rows: rawReport.rows.where((r) => _selectedVehicleIds.contains(r.vehicle.id)).toList(),
          );

    return Scaffold(
      appBar: AppBar(title: const Text('Fuel Report')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          Row(
            children: [
              Expanded(
                child: OutlinedButton(
                  onPressed: () => _pickDate(isStart: true),
                  child: Text(_startDate == null ? 'Start date' : _dateFormat.format(_startDate!)),
                ),
              ),
              const SizedBox(width: 12),
              Expanded(
                child: OutlinedButton(
                  onPressed: () => _pickDate(isStart: false),
                  child: Text(_endDate == null ? 'End date' : _dateFormat.format(_endDate!)),
                ),
              ),
            ],
          ),
          if (rangeError != null) ...[
            const SizedBox(height: 8),
            Text(rangeError, style: TextStyle(color: Theme.of(context).colorScheme.error)),
          ],
          const SizedBox(height: 8),
          SwitchListTile(
            contentPadding: EdgeInsets.zero,
            title: const Text('Include Receipt Images'),
            subtitle: const Text(
              'Every receipt photo in the date range, grouped by vehicle and '
              'sorted by date — packed as many to a page as will fit.',
            ),
            value: _includeReceiptImages,
            onChanged: (value) => setState(() => _includeReceiptImages = value),
          ),
          SwitchListTile(
            contentPadding: EdgeInsets.zero,
            title: const Text('Include Receipt Line Items'),
            subtitle: const Text(
              'Every receipt as its own line (date, gallons, price/gal, '
              'cost), grouped by vehicle and sorted by date.',
            ),
            value: _includeLineItems,
            onChanged: (value) => setState(() => _includeLineItems = value),
          ),
          if (_includeReceiptImages && _includeLineItems)
            Padding(
              padding: const EdgeInsets.only(bottom: 8),
              child: Text(
                'Each line item and its receipt photo will be tagged with a '
                'matching number.',
                style: Theme.of(context).textTheme.bodySmall,
              ),
            ),
          const SizedBox(height: 8),
          if (rawReport == null)
            const Padding(
              padding: EdgeInsets.symmetric(vertical: 24),
              child: Text('Choose a start and end date to generate a report.'),
            )
          else if (rawReport.rows.isEmpty)
            const Padding(
              padding: EdgeInsets.symmetric(vertical: 24),
              child: Text('No vehicles had a receipted fuel entry in that date range.'),
            )
          else ...[
            for (final row in rawReport.rows)
              _VehicleSelectionCard(
                row: row,
                selected: _selectedVehicleIds.contains(row.vehicle.id),
                onTap: () => setState(() {
                  if (_selectedVehicleIds.contains(row.vehicle.id)) {
                    _selectedVehicleIds.remove(row.vehicle.id);
                  } else {
                    _selectedVehicleIds.add(row.vehicle.id);
                  }
                }),
              ),
            const Divider(height: 32),
            if (report!.rows.isEmpty)
              const Padding(
                padding: EdgeInsets.symmetric(vertical: 24),
                child: Text('No vehicles selected — tap at least one above to build a report.'),
              )
            else ...[
              ListTile(
                title: const Text('Total', style: TextStyle(fontWeight: FontWeight.bold)),
                trailing: Text(
                  '${report.totalGallons.toStringAsFixed(3)} gal · '
                  '${NumberFormat.simpleCurrency().format(report.totalCost)}',
                  style: const TextStyle(fontWeight: FontWeight.bold),
                ),
              ),
              const SizedBox(height: 16),
              Row(
                children: [
                  Expanded(
                    child: FilledButton.icon(
                      onPressed: _busy ? null : () => _share(report),
                      icon: const Icon(Icons.share_outlined),
                      label: const Text('Share'),
                    ),
                  ),
                  const SizedBox(width: 12),
                  Expanded(
                    child: OutlinedButton.icon(
                      onPressed: _busy ? null : () => _print(report),
                      icon: const Icon(Icons.print_outlined),
                      label: const Text('Print'),
                    ),
                  ),
                ],
              ),
            ],
          ],
          const SizedBox(height: 24),
          Card(
            child: Padding(
              padding: const EdgeInsets.all(16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('Need the refund claim form?', style: Theme.of(context).textTheme.titleMedium),
                  const SizedBox(height: 8),
                  Text(
                    "This app tracks your fuel purchases, but the actual refund claim is "
                    "filed with the state. Get the official form from Missouri's "
                    'Department of Revenue website.',
                    style: Theme.of(context).textTheme.bodyMedium,
                  ),
                  const SizedBox(height: 12),
                  InkWell(
                    onTap: _openRefundFormLink,
                    child: Row(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        Icon(Icons.open_in_new, size: 18, color: Theme.of(context).colorScheme.primary),
                        const SizedBox(width: 6),
                        Flexible(
                          child: Text(
                            'Get the Motor Fuel Refund Claim form',
                            style: TextStyle(
                              color: Theme.of(context).colorScheme.primary,
                              fontWeight: FontWeight.w600,
                              decoration: TextDecoration.underline,
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

/// A per-vehicle row in the vehicle-selection list — tapping the whole
/// card toggles [selected], indicated purely by color rather than a
/// checkbox: [selected] uses the same primary/on-primary theming as the
/// "Share" [FilledButton] below it, [!selected] looks like a plain
/// unselected [Card] (default surface color, normal text colors).
class _VehicleSelectionCard extends StatelessWidget {
  final VehicleReportRow row;
  final bool selected;
  final VoidCallback onTap;

  const _VehicleSelectionCard({required this.row, required this.selected, required this.onTap});

  @override
  Widget build(BuildContext context) {
    final colorScheme = Theme.of(context).colorScheme;
    final foreground = selected ? colorScheme.onPrimary : colorScheme.onSurface;
    final foregroundVariant = selected ? colorScheme.onPrimary : colorScheme.onSurfaceVariant;

    return Card(
      color: selected ? colorScheme.primary : null,
      clipBehavior: Clip.antiAlias,
      child: InkWell(
        onTap: onTap,
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
          child: Row(
            children: [
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Text(
                      row.vehicle.displayLabel,
                      style: TextStyle(color: foreground, fontWeight: FontWeight.w600, fontSize: 16),
                    ),
                    const SizedBox(height: 2),
                    Text(
                      'VIN: ${row.vehicle.vin}\n${row.entryCount} receipted '
                      'entr${row.entryCount == 1 ? 'y' : 'ies'}',
                      style: TextStyle(color: foregroundVariant),
                    ),
                  ],
                ),
              ),
              Column(
                crossAxisAlignment: CrossAxisAlignment.end,
                children: [
                  Text('${row.totalGallons.toStringAsFixed(3)} gal', style: TextStyle(color: foreground)),
                  Text(
                    NumberFormat.simpleCurrency().format(row.totalCost),
                    style: TextStyle(color: foreground),
                  ),
                ],
              ),
            ],
          ),
        ),
      ),
    );
  }
}