/*
	Spacebar: A FOSS re-implementation and extension of the Discord.com backend.
	Copyright (C) 2023 Spacebar and Spacebar Contributors
	
	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published
	by the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.
	
	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

type Location = { latitude: number; longitude: number };
export function distanceBetweenLocations(loc1: Location, loc2: Location): number {
	return distanceBetweenCoords(loc1.latitude, loc1.longitude, loc2.latitude, loc2.longitude);
}

//Haversine function
function distanceBetweenCoords(lat1: number, lon1: number, lat2: number, lon2: number) {
	const p = 0.017453292519943295; // Math.PI / 180
	const c = Math.cos;
	const a = 0.5 - c((lat2 - lat1) * p) / 2 + (c(lat1 * p) * c(lat2 * p) * (1 - c((lon2 - lon1) * p))) / 2;

	return 12742 * Math.asin(Math.sqrt(a)); // 2 * R; R = 6371 km
}