Mathematics

const CEILING = 150; // Elo delta ceiling
const FLOOR = 25; // Elo delta floor
 
/***
 * Function that matches two teams against each other
 * @param R_A - Team A's current Elo (ex: 1300)
 * @param R_B - Team B's current Elo (ex: 1500)
 * @param m_A - Team A's rounds (ex: 3)
 * @param m_B - Team B's rounds (ex: 0)
 */
function match(R_A: number, R_B: number, m_A: number, m_B: number) {
	// Algorithm as specified in the docs
	const alg: number = R_A + CEILING * ((m_A / (m_A + m_B)) - (1 / (1 + 10 ** ((R_B - R_A) / 400)))) + FLOOR * ((m_A - m_B) / Math.abs(m_A - m_B));
 
	// Ensure change in elo is always positive for the winner
	let delta: number = Math.abs(alg - R_A);
 
	// Ensure change in elo is greater than or equal to the floor
	if (delta < FLOOR) delta = FLOOR;
 
	// Ensure change in elo is less than or equal to the ceiling
	if (delta > CEILING) delta = CEILING;
 
	const results: MatchResults = {
		winnerEloOld: R_A,
		loserEloOld: R_B,
		rounds: [m_A, m_B],
		deltaElo: delta,
		winnerElo: R_A + delta,
		loserElo: R_B - delta
	};
 
	return results;
}