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//
// Midpoint.swift
// RelaySelector
//
// Created by Marco Nikic on 2023-07-11.
// Copyright © 2025 Mullvad VPN AB. All rights reserved.
//
import CoreLocation
import Foundation
import MullvadTypes
public enum Midpoint {
/// Computes the approximate midpoint of a set of locations.
///
/// This works by calculating the mean Cartesian coordinates, and converting them
/// back to spherical coordinates. This is approximate, because the semi-minor (polar)
/// axis is assumed to equal the semi-major (equatorial) axis.
///
/// https://en.wikipedia.org/wiki/Spherical_coordinate_system#Cartesian_coordinates
static func location(in coordinates: [CLLocationCoordinate2D]) -> CLLocationCoordinate2D {
var x = 0.0
var y = 0.0
var z = 0.0
var count = 0
coordinates.forEach { coordinate in
let cos_lat = cos(coordinate.latitude.toRadians)
let sin_lat = sin(coordinate.latitude.toRadians)
let cos_lon = cos(coordinate.longitude.toRadians)
let sin_lon = sin(coordinate.longitude.toRadians)
x += cos_lat * cos_lon
y += cos_lat * sin_lon
z += sin_lat
count += 1
}
let inv_total_weight = 1.0 / Double(count)
x *= inv_total_weight
y *= inv_total_weight
z *= inv_total_weight
let longitude = atan2(y, x)
let hypotenuse = sqrt(x * x + y * y)
let latitude = atan2(z, hypotenuse)
return CLLocationCoordinate2D(latitude: latitude.toDegrees, longitude: longitude.toDegrees)
}
}
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