brackt/app/services/simulations/ncaam-simulator.ts

import { NCAABasketballSimulator } from "./ncaa-basketball-simulator";
import type { Simulator, SimulationResult } from "./types";

const KENPOM_SCALE_FACTOR = 7.5;

/**
 * NCAAM neutral-court win probability using a KenPom-like adjusted efficiency
 * margin. Ratings are season-scoped simulator inputs, not hardcoded data.
 */
export function kenpomWinProbability(netrtgA: number, netrtgB: number): number {
  return 1 / (1 + Math.exp(-(netrtgA - netrtgB) / KENPOM_SCALE_FACTOR));
}

function optionalPositiveNumber(value: unknown, fallback: number): number {
  return typeof value === "number" && Number.isFinite(value) && value > 0 ? value : fallback;
}

function kenpomWinProbabilityWithScale(scaleFactor: number): (netrtgA: number, netrtgB: number) => number {
  return (netrtgA, netrtgB) => 1 / (1 + Math.exp(-(netrtgA - netrtgB) / scaleFactor));
}

export class NCAAMSimulator implements Simulator {
  private readonly simulator = new NCAABasketballSimulator({
    source: "ncaam_bracket_rating",
    missingRatingName: "KenPom-like rating",
    selectionRatingDivisor: 8,
    winProbability: kenpomWinProbability,
    getWinProbability: (config) =>
      kenpomWinProbabilityWithScale(optionalPositiveNumber(config.ratingScaleFactor, KENPOM_SCALE_FACTOR)),
  });

  simulate(sportsSeasonId: string): Promise<SimulationResult[]> {
    return this.simulator.simulate(sportsSeasonId);
  }
}