import 'dart:io';
import 'package:latlong2/latlong.dart';
import 'package:path_provider/path_provider.dart';
import '../models/stop.dart';

class GpxExportService {
  /// Export route stops as GPX file with waypoints and optional track.
  /// Returns the file path of the saved GPX file.
  static Future<String> exportRoute({
    required String routeName,
    required List<Stop> stops,
    List<LatLng>? trackPoints,
  }) async {
    final buffer = StringBuffer();

    buffer.writeln('<?xml version="1.0" encoding="UTF-8"?>');
    buffer.writeln(
        '<gpx version="1.1" creator="Delivery Route App" xmlns="http://www.topografix.com/GPX/1/1">');
    buffer.writeln('  <metadata>');
    buffer.writeln('    <name>${_escapeXml(routeName)}</name>');
    buffer.writeln('    <time>${DateTime.now().toUtc().toIso8601String()}</time>');
    buffer.writeln('  </metadata>');

    // Waypoints
    for (final stop in stops) {
      buffer.writeln('  <wpt lat="${stop.lat}" lon="${stop.lng}">');
      buffer.writeln('    <name>${_escapeXml(stop.street)} ${_escapeXml(stop.houseNumber)}</name>');
      if (stop.newspapers.isNotEmpty) {
        buffer.writeln('    <desc>${_escapeXml(stop.newspapers.join(', '))}</desc>');
      }
      if (stop.notes.isNotEmpty) {
        buffer.writeln('    <cmt>${_escapeXml(stop.notes)}</cmt>');
      }
      buffer.writeln('  </wpt>');
    }

    // Track (if route points available)
    if (trackPoints != null && trackPoints.isNotEmpty) {
      buffer.writeln('  <trk>');
      buffer.writeln('    <name>${_escapeXml(routeName)} - Route</name>');
      buffer.writeln('    <trkseg>');
      for (final point in trackPoints) {
        buffer.writeln(
            '      <trkpt lat="${point.latitude}" lon="${point.longitude}"></trkpt>');
      }
      buffer.writeln('    </trkseg>');
      buffer.writeln('  </trk>');
    }

    buffer.writeln('</gpx>');

    // Save to file
    final directory = await getApplicationDocumentsDirectory();
    final sanitized = routeName.replaceAll(RegExp(r'[^\w\s-]'), '').replaceAll(' ', '_');
    final fileName = 'route_${sanitized}_${_dateStamp()}.gpx';
    final file = File('${directory.path}/$fileName');
    await file.writeAsString(buffer.toString());

    return file.path;
  }

  static String _escapeXml(String text) {
    return text
        .replaceAll('&', '&amp;')
        .replaceAll('<', '&lt;')
        .replaceAll('>', '&gt;')
        .replaceAll('"', '&quot;')
        .replaceAll("'", '&apos;');
  }

  static String _dateStamp() {
    final now = DateTime.now();
    return '${now.year}${now.month.toString().padLeft(2, '0')}${now.day.toString().padLeft(2, '0')}_${now.hour.toString().padLeft(2, '0')}${now.minute.toString().padLeft(2, '0')}';
  }
}