115 lines
3.5 KiB
Dart
115 lines
3.5 KiB
Dart
import "dart:convert";
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import "dart:math";
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import "package:photos/core/constants.dart";
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import "package:photos/models/location/location.dart";
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import 'package:photos/models/location_tag/location_tag.dart';
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import "package:shared_preferences/shared_preferences.dart";
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class LocationService {
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late SharedPreferences prefs;
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LocationService._privateConstructor();
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static final LocationService instance = LocationService._privateConstructor();
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void init(SharedPreferences preferences) {
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prefs = preferences;
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}
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List<String> _getStoredLocationTags() {
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var list = prefs.getStringList('locations');
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list ??= [];
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return list;
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}
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List<LocationTag> getLocationTags() {
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final list = _getStoredLocationTags();
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return list.map((e) => LocationTag.fromJson(json.decode(e))).toList();
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}
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Future<void> addLocation(
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String location,
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Location centerPoint,
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int radius,
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) async {
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final list = _getStoredLocationTags();
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//The area enclosed by the location tag will be a circle on a 3D spherical
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//globe and an ellipse on a 2D Mercator projection (2D map)
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//a & b are the semi-major and semi-minor axes of the ellipse
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//Converting the unit from kilometers to degrees for a and b as that is
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//the unit on the caritesian plane
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final a =
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(radius * _scaleFactor(centerPoint.latitude!)) / kilometersPerDegree;
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final b = radius / kilometersPerDegree;
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final locationTag = LocationTag(
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name: location,
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radius: radius,
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aSquare: a * a,
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bSquare: b * b,
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centerPoint: centerPoint,
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);
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list.add(json.encode(locationTag.toJson()));
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await prefs.setStringList('locations', list);
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}
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///The area bounded by the location tag becomes more elliptical with increase
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///in the magnitude of the latitude on the caritesian plane. When latitude is
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///0 degrees, the ellipse is a circle with a = b = r. When latitude incrases,
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///the major axis (a) has to be scaled by the secant of the latitude.
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double _scaleFactor(double lat) {
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return 1 / cos(lat * (pi / 180));
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}
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List<LocationTag> enclosingLocationTags(Location fileCoordinates) {
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final result = List<LocationTag>.of([]);
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final locationTagsData = getLocationTags();
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for (LocationTag locationTag in locationTagsData) {
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final x = fileCoordinates.latitude! - locationTag.centerPoint.latitude!;
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final y = fileCoordinates.longitude! - locationTag.centerPoint.longitude!;
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if ((x * x) / (locationTag.aSquare) + (y * y) / (locationTag.bSquare) <=
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1) {
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result.add(
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locationTag,
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);
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}
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}
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return result;
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}
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bool isFileInsideLocationTag(
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Location centerPoint,
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Location fileCoordinates,
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int radius,
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) {
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final a =
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(radius * _scaleFactor(centerPoint.latitude!)) / kilometersPerDegree;
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final b = radius / kilometersPerDegree;
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final x = centerPoint.latitude! - fileCoordinates.latitude!;
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final y = centerPoint.longitude! - fileCoordinates.longitude!;
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if ((x * x) / (a * a) + (y * y) / (b * b) <= 1) {
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return true;
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}
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return false;
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}
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}
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class GPSData {
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final String latRef;
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final List<double> lat;
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final String longRef;
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final List<double> long;
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GPSData(this.latRef, this.lat, this.longRef, this.long);
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Location toLocationFormat() {
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final latSign = latRef == "N" ? 1 : -1;
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final longSign = longRef == "E" ? 1 : -1;
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return Location(
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latitude: latSign * lat[0] + lat[1] / 60 + lat[2] / 3600,
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longitude: longSign * long[0] + long[1] / 60 + long[2] / 3600,
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);
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}
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}
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