import { timingSafeEqual } from 'crypto';

export type Difficulty = 'LOW' | 'MEDIUM' | 'HIGH';

export const DIFFICULTY_RANK: Readonly<Record<Difficulty, number>> = {
  LOW: 0,
  MEDIUM: 1,
  HIGH: 2,
};

export function compareDifficulty(a: Difficulty, b: Difficulty): number {
  return DIFFICULTY_RANK[a] - DIFFICULTY_RANK[b];
}

export function computeLivePoints(
  initial: number,
  minimum: number,
  decaySolves: number,
  currentSolveCount: number,
): number {
  if (!Number.isFinite(initial) || !Number.isFinite(minimum)) return minimum;
  const i = Math.max(0, Math.floor(initial));
  const m = Math.max(0, Math.floor(minimum));
  const d = Math.max(0, Math.floor(decaySolves));
  const c = Math.max(0, Math.floor(currentSolveCount));
  if (i < m) return Math.max(0, m);
  if (d <= 0) return i;
  if (c >= d) return m;
  const span = i - m;
  const raw = i - span * (c / d);
  return Math.max(m, Math.round(raw));
}

export function rankBonusForPosition(position: number): number {
  if (!Number.isInteger(position) || position <= 0) return 0;
  if (position === 1) return 15;
  if (position === 2) return 10;
  if (position === 3) return 5;
  return 0;
}

export function safeEqualString(a: string, b: string): boolean {
  const ab = Buffer.from(a, 'utf8');
  const bb = Buffer.from(b, 'utf8');
  if (ab.length !== bb.length) {
    let diff = ab.length ^ bb.length;
    const max = Math.max(ab.length, bb.length);
    for (let i = 0; i < max; i += 1) {
      diff |= (ab[i] ?? 0) ^ (bb[i] ?? 0);
    }
    return false;
  }
  return timingSafeEqual(ab, bb);
}