import type { SaveV1 } from "./types";

import {
  LAST_PLAYABLE,
  freshSave,
  migrateSubIndex,
  subCount,
} from "./levels";

export const STORAGE_KEY = "folder-game-challenge:v1";

export function parseSave(raw: string | null): SaveV1 | null {
  if (!raw) return null;
  try {
    const v = JSON.parse(raw) as SaveV1;
    if (v?.version !== 1) return null;
    if (typeof v.levelIndex !== "number") return null;
    if (v.levelIndex < 0 || v.levelIndex > LAST_PLAYABLE + 1) return null;
    if (!v.fs?.nodes || typeof v.fs.viewParentId !== "string") return null;
    if (!Array.isArray(v.fs.visitedFolderIds)) return null;
    const subIndex = migrateSubIndex(
      v.levelIndex,
      v.fs,
      typeof v.subIndex === "number" ? v.subIndex : undefined,
    );
    const maxSub = Math.max(0, subCount(v.levelIndex) - 1);
    return { ...v, subIndex: Math.min(subIndex, maxSub) };
  } catch {
    return null;
  }
}

export function loadSave(): SaveV1 | null {
  if (typeof window === "undefined") return null;
  return parseSave(localStorage.getItem(STORAGE_KEY));
}

export function writeSave(save: SaveV1) {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(save));
}

export function clearSave() {
  localStorage.removeItem(STORAGE_KEY);
}

export function resumeOrNew(): SaveV1 {
  return loadSave() ?? freshSave(0);
}

export function hasInProgressSave(): boolean {
  const s = loadSave();
  return s !== null && s.levelIndex <= LAST_PLAYABLE;
}

export function isFinished(save: SaveV1) {
  return save.levelIndex > LAST_PLAYABLE;
}