/**
 * 数据存储层（JSON 文件落盘）
 * -------------------------------------------------------------
 * 集合：
 *   bookings  —— 公益课报名 / 沙龙预约（前端预约表单）
 *   events    —— 公益课 + 沙龙排期（后台可增删改）
 *   tests     —— OPC 测评记录（前端测评上报）
 * 说明：
 *   - 同步读写在数据量小的阶段足够；迁移真实数据库时替换本文件实现即可。
 *   - 带内存缓存，避免每次请求都读文件。
 */
import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'node:fs';
import { fileURLToPath } from 'node:url';
import path from 'node:path';

const DIR = path.dirname(fileURLToPath(import.meta.url));
const FILES = {
  accounts: path.join(DIR, 'accounts.json'),
  bookings: path.join(DIR, 'bookings.json'),
  events: path.join(DIR, 'events.json'),
  tests: path.join(DIR, 'tests.json'),
  policyLogs: path.join(DIR, 'policyLogs.json'),
  planLogs: path.join(DIR, 'planLogs.json'),
  surveyLogs: path.join(DIR, 'surveyLogs.json')
};

const CACHE = {};

function ensureFile(key) {
  const file = FILES[key];
  if (!file) throw new Error('unknown store: ' + key);
  if (!existsSync(file)) {
    mkdirSync(path.dirname(file), { recursive: true });
    writeFileSync(file, '[]', 'utf8');
  }
  return file;
}

export function loadAll(key) {
  if (CACHE[key] !== undefined) return CACHE[key];
  const file = ensureFile(key);
  try {
    CACHE[key] = JSON.parse(readFileSync(file, 'utf8') || '[]');
  } catch {
    CACHE[key] = [];
  }
  if (!Array.isArray(CACHE[key])) CACHE[key] = [];
  return CACHE[key];
}

export function save(key, list) {
  CACHE[key] = Array.isArray(list) ? list : [];
  const file = ensureFile(key);
  writeFileSync(file, JSON.stringify(CACHE[key], null, 2), 'utf8');
}

export function add(key, entry) {
  const list = loadAll(key);
  list.push(entry);
  save(key, list);
  return entry;
}

export function update(key, id, patch) {
  const list = loadAll(key);
  const i = list.findIndex((x) => x.id === id);
  if (i < 0) return null;
  list[i] = { ...list[i], ...patch, id };
  save(key, list);
  return list[i];
}

export function remove(key, id) {
  const list = loadAll(key);
  const next = list.filter((x) => x.id !== id);
  if (next.length === list.length) return false;
  save(key, next);
  return true;
}

/** 首次运行注入种子数据（仅当集合为空时） */
export function seedIfEmpty(key, seed) {
  if (loadAll(key).length === 0) save(key, seed);
}