import { eloWinProbabilityWithParity } from "~/services/probability-engine";

export type SoccerMatchResult = "win" | "draw" | "loss";

export interface EloSoccerMatchOptions {
  baseDrawRate: number;
  drawDecay: number;
  parityFactor?: number;
}

export function soccerDrawProbability(
  eloA: number,
  eloB: number,
  baseDrawRate: number,
  drawDecay: number
): number {
  return baseDrawRate * Math.exp(-drawDecay * Math.abs(eloA - eloB));
}

/**
 * Simulate a soccer-style Elo match with an explicit draw probability.
 * Returns the result from team A's perspective.
 */
export function simulateEloSoccerMatch(
  eloA: number,
  eloB: number,
  { baseDrawRate, drawDecay, parityFactor = 400 }: EloSoccerMatchOptions
): SoccerMatchResult {
  const pDraw = soccerDrawProbability(eloA, eloB, baseDrawRate, drawDecay);
  const pWinNoDraw = eloWinProbabilityWithParity(eloA, eloB, parityFactor);
  const pWin = (1 - pDraw) * pWinNoDraw;
  const rand = Math.random();
  if (rand < pWin) return "win";
  if (rand < pWin + pDraw) return "draw";
  return "loss";
}

/** Generate simple low-scoring goals for table tiebreakers after a result is known. */
export function simulateSimpleSoccerGoals(result: SoccerMatchResult): { gf: number; ga: number } {
  if (result === "draw") {
    const goals = Math.random() < 0.55 ? 1 : Math.random() < 0.75 ? 0 : 2;
    return { gf: goals, ga: goals };
  }

  const winnerGoals = Math.random() < 0.55 ? 2 : Math.random() < 0.75 ? 1 : 3;
  const loserGoals = winnerGoals === 1 ? 0 : Math.random() < 0.35 ? 1 : 0;
  if (result === "win") return { gf: winnerGoals, ga: loserGoals };
  return { gf: loserGoals, ga: winnerGoals };
}