export interface GameStats {
  streak: number;
  lastDate: string; // ISO date YYYY-MM-DD
  total: number;
  bestTime: number; // seconds, 0 = never recorded
}

const DEFAULT: GameStats = { streak: 0, lastDate: "", total: 0, bestTime: 0 };

function storageKey(game: string) { return `stats-${game}`; }

export function loadStats(game: string): GameStats {
  if (typeof window === "undefined") return DEFAULT;
  try {
    const raw = localStorage.getItem(storageKey(game));
    if (!raw) return DEFAULT;
    return { ...DEFAULT, ...JSON.parse(raw) };
  } catch { return DEFAULT; }
}

export function recordSolve(game: string, date: string, secs: number): GameStats {
  const prev = loadStats(game);

  // Compute yesterday ISO using local-date arithmetic (avoids UTC offset bug)
  const [y, m, d] = date.split("-").map(Number);
  const prev2 = new Date(y, m - 1, d - 1); // local date, no UTC issue
  const yesterdayISO = `${prev2.getFullYear()}-${String(prev2.getMonth() + 1).padStart(2, "0")}-${String(prev2.getDate()).padStart(2, "0")}`;

  let streak = prev.streak;
  if (prev.lastDate === date) {
    // Already solved today — don't double-count
  } else if (prev.lastDate === yesterdayISO) {
    streak += 1;
  } else {
    streak = 1;
  }

  const stats: GameStats = {
    streak,
    lastDate: date,
    total: prev.lastDate === date ? prev.total : prev.total + 1,
    bestTime: prev.bestTime === 0 || secs < prev.bestTime ? secs : prev.bestTime,
  };
  localStorage.setItem(storageKey(game), JSON.stringify(stats));
  return stats;
}