elo.py

import math
from typing import Tuple

def calculate_elo(
    rating_a: float, 
    rating_b: float, 
    score_a: float, 
    k_factor: int = 32
) -> Tuple[float, float]:
    """
    Calculates the new ELO ratings for two participants.

    Args:
        rating_a: Current rating of participant A.
        rating_b: Current rating of participant B.
        score_a: Score for participant A (1.0 for win, 0.5 for tie, 0.0 for loss).
        k_factor: The K-factor determines how much the ratings change.

    Returns:
        A tuple containing (new_rating_a, new_rating_b).
    """
    expected_a = 1 / (1 + math.pow(10, (rating_b - rating_a) / 400))
    expected_b = 1 - expected_a

    score_b = 1 - score_a

    new_rating_a = rating_a + k_factor * (score_a - expected_a)
    new_rating_b = rating_b + k_factor * (score_b - expected_b)

    return round(new_rating_a, 2), round(new_rating_b, 2)