StikDebug/StikJIT/Utilities/CoordinateTransform.swift

import Foundation
import CoreLocation

enum CoordinateTransform {
    private static let pi = Double.pi
    private static let a = 6378245.0
    private static let ee = 0.00669342162296594323

    static func wgs84ToGCJ02(_ coordinate: CLLocationCoordinate2D) -> CLLocationCoordinate2D {
        let lat = coordinate.latitude
        let lon = coordinate.longitude
        let dLat = transformLat(x: lon - 105.0, y: lat - 35.0)
        let dLon = transformLon(x: lon - 105.0, y: lat - 35.0)
        let radLat = lat / 180.0 * pi
        let sinRadLat = sin(radLat)
        let magic = 1 - ee * sinRadLat * sinRadLat
        let sqrtMagic = sqrt(magic)
        let adjustedLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi)
        let adjustedLon = (dLon * 180.0) / (a / sqrtMagic * cos(radLat) * pi)
        return CLLocationCoordinate2D(
            latitude: lat + adjustedLat,
            longitude: lon + adjustedLon
        )
    }

    static func wgs84ToGCJ02(_ coordinates: [CLLocationCoordinate2D]) -> [CLLocationCoordinate2D] {
        coordinates.map { wgs84ToGCJ02($0) }
    }

    static func gcj02ToWGS84(_ coordinate: CLLocationCoordinate2D) -> CLLocationCoordinate2D {
        let gcjLat = coordinate.latitude
        let gcjLon = coordinate.longitude
        let dLat = transformLat(x: gcjLon - 105.0, y: gcjLat - 35.0)
        let dLon = transformLon(x: gcjLon - 105.0, y: gcjLat - 35.0)
        let radLat = gcjLat / 180.0 * pi
        let sinRadLat = sin(radLat)
        let magic = 1 - ee * sinRadLat * sinRadLat
        let sqrtMagic = sqrt(magic)
        let adjustedLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi)
        let adjustedLon = (dLon * 180.0) / (a / sqrtMagic * cos(radLat) * pi)
        return CLLocationCoordinate2D(
            latitude: gcjLat - adjustedLat,
            longitude: gcjLon - adjustedLon
        )
    }

    private static func transformLat(x: Double, y: Double) -> Double {
        var ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * sqrt(abs(x))
        ret += (20.0 * sin(6.0 * x * pi) + 20.0 * sin(2.0 * x * pi)) * 2.0 / 3.0
        ret += (20.0 * sin(y * pi) + 40.0 * sin(y / 3.0 * pi)) * 2.0 / 3.0
        ret += (160.0 * sin(y / 12.0 * pi) + 320.0 * sin(y * pi / 30.0)) * 2.0 / 3.0
        return ret
    }

    private static func transformLon(x: Double, y: Double) -> Double {
        var ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * sqrt(abs(x))
        ret += (20.0 * sin(6.0 * x * pi) + 20.0 * sin(2.0 * x * pi)) * 2.0 / 3.0
        ret += (20.0 * sin(x * pi) + 40.0 * sin(x / 3.0 * pi)) * 2.0 / 3.0
        ret += (150.0 * sin(x / 12.0 * pi) + 300.0 * sin(x / 30.0 * pi)) * 2.0 / 3.0
        return ret
    }
}