import { GAMES, GameId } from "@/lib/levels";

export type PlayMode = "free" | "session";

export function getPlayMode(): PlayMode {
  if (typeof window === "undefined") return "free";
  return (localStorage.getItem("pt-mode") as PlayMode) ?? "free";
}

export function savePlayMode(mode: PlayMode) {
  localStorage.setItem("pt-mode", mode);
}

/**
 * Session order for a given date: rotates the starting game each day.
 * Day 0 → Q T Z S P, Day 1 → T Z S P Q, etc.
 */
export function getSessionOrder(date: string): GameId[] {
  const [y, m, d] = date.split("-").map(Number);
  const dayNum = Math.floor(Date.UTC(y, m - 1, d) / 86400000);
  const start = dayNum % GAMES.length;
  return [...GAMES.slice(start), ...GAMES.slice(0, start)];
}

/** Returns the next unsolved game in the session order, or null if all done / not in session mode. */
export function getNextSessionGame(currentGame: string, date: string): GameId | null {
  if (typeof window === "undefined") return null;
  if (getPlayMode() !== "session") return null;

  const order = getSessionOrder(date);
  const currentIdx = order.indexOf(currentGame as GameId);
  if (currentIdx === -1) return null;

  for (let i = currentIdx + 1; i < order.length; i++) {
    const g = order[i];
    try {
      const raw = localStorage.getItem(`stats-${g}`);
      const lastDate = raw ? JSON.parse(raw)?.lastDate : null;
      if (lastDate !== date) return g; // not yet solved today
    } catch { return g; }
  }
  return null; // all remaining games solved
}