maps-saas/packages/tactical_app/lib/services/military_grid_utils.dart

import 'dart:math' as math;
import 'package:intaleq_maps/intaleq_maps.dart';

/// Military Coordinates Utility (WGS84 <-> UTM Zone 36N & MGRS Grid)
/// Specifically optimized for Jordan & Levantine military operations (Zone 36N / 37N)
class MilitaryGridUtils {
  MilitaryGridUtils._();

  static const double _a = 6378137.0; // WGS84 semi-major axis
  static const double _f = 1 / 298.257223563; // WGS84 flattening
  static const double _b = _a * (1.0 - _f);
  static const double _eSq = (_a * _a - _b * _b) / (_a * _a);
  static const double _ePrimeSq = (_a * _a - _b * _b) / (_b * _b);
  static const double _k0 = 0.9996; // UTM scale factor

  /// Convert WGS84 Lat/Lng to UTM Zone 36N Easting (شرقيات) and Northing (شماليات)
  static MilitaryCoordinates fromLatLng(LatLng latLng, {int zone = 36}) {
    final lat = latLng.latitude;
    final lng = latLng.longitude;

    final latRad = lat * (math.pi / 180.0);
    final lngRad = lng * (math.pi / 180.0);

    final centralMeridianDeg = (zone - 1) * 6 - 180 + 3;
    final centralMeridianRad = centralMeridianDeg * (math.pi / 180.0);

    final n = _a / math.sqrt(1.0 - _eSq * math.sin(latRad) * math.sin(latRad));
    final t = math.tan(latRad) * math.tan(latRad);
    final c = _ePrimeSq * math.cos(latRad) * math.cos(latRad);
    final aCoeff = math.cos(latRad) * (lngRad - centralMeridianRad);

    final m = _a *
        ((1.0 -
                _eSq / 4.0 -
                3.0 * _eSq * _eSq / 64.0 -
                5.0 * _eSq * _eSq * _eSq / 256.0) *
            latRad -
            (3.0 * _eSq / 8.0 +
                3.0 * _eSq * _eSq / 32.0 +
                45.0 * _eSq * _eSq * _eSq / 1024.0) *
                math.sin(2.0 * latRad) +
            (15.0 * _eSq * _eSq / 256.0 +
                45.0 * _eSq * _eSq * _eSq / 1024.0) *
                math.sin(4.0 * latRad) -
            (35.0 * _eSq * _eSq * _eSq / 3072.0) * math.sin(6.0 * latRad));

    final easting = 500000.0 +
        _k0 *
            n *
            (aCoeff +
                (1.0 - t + c) * math.pow(aCoeff, 3) / 6.0 +
                (5.0 - 18.0 * t + t * t + 72.0 * c - 58.0 * _ePrimeSq) *
                    math.pow(aCoeff, 5) /
                    120.0);

    final northing = _k0 *
        (m +
            n *
                math.tan(latRad) *
                (aCoeff * aCoeff / 2.0 +
                    (5.0 - t + 9.0 * c + 4.0 * c * c) *
                        math.pow(aCoeff, 4) /
                        24.0 +
                    (61.0 - 58.0 * t + t * t + 600.0 * c - 330.0 * _ePrimeSq) *
                        math.pow(aCoeff, 6) /
                        720.0));

    return MilitaryCoordinates(
      lat: lat,
      lng: lng,
      easting: easting,
      northing: northing,
      zone: zone,
    );
  }

  /// Convert UTM Zone 36N Easting (شرقيات) and Northing (شماليات) to WGS84 Lat/Lng
  static LatLng toLatLng({
    required double easting,
    required double northing,
    int zone = 36,
  }) {
    final e1 = (1.0 - math.sqrt(1.0 - _eSq)) / (1.0 + math.sqrt(1.0 - _eSq));
    final x = easting - 500000.0;
    final y = northing;

    final m = y / _k0;
    final mu = m /
        (_a *
            (1.0 -
                _eSq / 4.0 -
                3.0 * _eSq * _eSq / 64.0 -
                5.0 * _eSq * _eSq * _eSq / 256.0));

    final phi1Rad = mu +
        (3.0 * e1 / 2.0 - 27.0 * math.pow(e1, 3) / 32.0) * math.sin(2.0 * mu) +
        (21.0 * e1 * e1 / 16.0 - 55.0 * math.pow(e1, 4) / 32.0) *
            math.sin(4.0 * mu) +
        (151.0 * math.pow(e1, 3) / 96.0) * math.sin(6.0 * mu) +
        (1097.0 * math.pow(e1, 4) / 512.0) * math.sin(8.0 * mu);

    final n1 = _a /
        math.sqrt(1.0 - _eSq * math.sin(phi1Rad) * math.sin(phi1Rad));
    final t1 = math.tan(phi1Rad) * math.tan(phi1Rad);
    final c1 = _ePrimeSq * math.cos(phi1Rad) * math.cos(phi1Rad);
    final r1 = _a *
        (1.0 - _eSq) /
        math.pow(1.0 - _eSq * math.sin(phi1Rad) * math.sin(phi1Rad), 1.5);
    final d = x / (n1 * _k0);

    final latRad = phi1Rad -
        (n1 * math.tan(phi1Rad) / r1) *
            (d * d / 2.0 -
                (5.0 + 3.0 * t1 + 10.0 * c1 - 4.0 * c1 * c1 - 9.0 * _ePrimeSq) *
                    math.pow(d, 4) /
                    24.0 +
                (61.0 +
                        90.0 * t1 +
                        298.0 * c1 +
                        45.0 * t1 * t1 -
                        252.0 * _ePrimeSq -
                        3.0 * c1 * c1) *
                    math.pow(d, 6) /
                    720.0);

    final centralMeridianDeg = (zone - 1) * 6 - 180 + 3;
    final centralMeridianRad = centralMeridianDeg * (math.pi / 180.0);

    final lngRad = centralMeridianRad +
        (d -
                (1.0 + 2.0 * t1 + c1) * math.pow(d, 3) / 6.0 +
                (5.0 -
                        2.0 * c1 +
                        28.0 * t1 -
                        3.0 * c1 * c1 +
                        8.0 * _ePrimeSq +
                        24.0 * t1 * t1) *
                    math.pow(d, 5) /
                    120.0) /
            math.cos(phi1Rad);

    return LatLng(
      latRad * (180.0 / math.pi),
      lngRad * (180.0 / math.pi),
    );
  }
}

class MilitaryCoordinates {
  final double lat;
  final double lng;
  final double easting;
  final double northing;
  final int zone;

  MilitaryCoordinates({
    required this.lat,
    required this.lng,
    required this.easting,
    required this.northing,
    this.zone = 36,
  });

  /// Short 6-digit Easting / Northing string for tactical voice transmission (e.g. 845 412)
  String get shortGrid =>
      '${(easting.round() % 100000 ~/ 100).toString().padLeft(3, '0')} ${(northing.round() % 100000 ~/ 100).toString().padLeft(3, '0')}';

  /// Standard Arabic military format (شرقيات: 784520 م • شماليات: 3541280 م)
  String get arabicFullFormat =>
      'شرقيات: ${easting.round()} م • شماليات: ${northing.round()} م (${zone}N)';

  String get eastingStr => '${easting.round()}';
  String get northingStr => '${northing.round()}';
}