pfm-ocr/lib/core/utils/exif_helper.dart

import 'dart:io';
import 'package:flutter/foundation.dart';
import 'package:exif/exif.dart';

class ExifHelper {
  /// Extracts GPS coordinates (latitude and longitude) from an image file's EXIF metadata.
  /// Returns a map with 'latitude' and 'longitude', or null if not found or invalid.
  static Future<Map<String, double>?> extractGps(String imagePath) async {
    try {
      final file = File(imagePath);
      if (!await file.exists()) {
        debugPrint('EXIF extract: File does not exist at $imagePath');
        return null;
      }

      final bytes = await file.readAsBytes();
      final tags = await readExifFromBytes(bytes);

      if (tags.isEmpty) {
        debugPrint('EXIF extract: No EXIF tags found in image');
        return null;
      }

      final latTag = tags['GPS GPSLatitude'];
      final latRefTag = tags['GPS GPSLatitudeRef'];
      final lngTag = tags['GPS GPSLongitude'];
      final lngRefTag = tags['GPS GPSLongitudeRef'];

      if (latTag == null || latRefTag == null || lngTag == null || lngRefTag == null) {
        debugPrint('EXIF extract: GPS tags missing in EXIF metadata');
        return null;
      }

      final double lat = _convertRatioListToDouble(latTag.values.toList());
      final double lng = _convertRatioListToDouble(lngTag.values.toList());

      final latRef = latRefTag.toString().trim().toUpperCase();
      final lngRef = lngRefTag.toString().trim().toUpperCase();

      double finalLat = lat;
      if (latRef == 'S') finalLat = -finalLat;

      double finalLng = lng;
      if (lngRef == 'W') finalLng = -finalLng;

      debugPrint('EXIF extract success: parsed coordinates Lat: $finalLat, Lng: $finalLng');
      return {
        'latitude': finalLat,
        'longitude': finalLng,
      };
    } catch (e) {
      debugPrint('Error parsing EXIF metadata: $e');
      return null;
    }
  }

  static double _convertRatioListToDouble(dynamic values) {
    if (values == null || values.length < 3) return 0.0;

    double degrees = _ratioToDouble(values[0]);
    double minutes = _ratioToDouble(values[1]);
    double seconds = _ratioToDouble(values[2]);

    return degrees + (minutes / 60.0) + (seconds / 3600.0);
  }

  static double _ratioToDouble(dynamic val) {
    if (val is Ratio) {
      return val.numerator / val.denominator;
    }
    if (val is num) {
      return val.toDouble();
    }
    final str = val.toString().trim();
    if (str.contains('/')) {
      final parts = str.split('/');
      if (parts.length == 2) {
        final numVal = double.tryParse(parts[0]) ?? 0.0;
        final denVal = double.tryParse(parts[1]) ?? 1.0;
        return numVal / denVal;
      }
    }
    return double.tryParse(str) ?? 0.0;
  }
}