/**
 * Persistent JSON store — backed by ./data/store.json (Docker volume mount).
 *
 * Schema:
 * {
 *   config: { eb_app_id, eb_private_key, gc_secret_id, gc_secret_key } | null,
 *   gc_tokens: { [token]: { type: "access"|"refresh", expires_at } },
 *   institutions_cache: [...] | null,
 *   institutions_cache_at: 0,
 *   agreements: { [gc_id]: { id, created, institution_id, max_historical_days,
 *                             access_valid_for_days, access_scope } },
 *   requisitions: { [gc_id]: { id, created, status, institution_id, agreements,
 *                               accounts, reference, redirect, link,
 *                               eb_auth_id, eb_session_id } },
 *   accounts: { [gc_id]: { gc_id, eb_uid, institution_id, iban, currency,
 *                           owner_name, name, product, created, last_accessed } }
 * }
 */

import { readFileSync, writeFileSync, mkdirSync, existsSync } from 'fs';
import { dirname } from 'path';

const STORE_PATH = process.env.STORE_PATH || './data/store.json';

const EMPTY = () => ({
  config: null,
  gc_tokens: {},
  institutions_cache: null,
  institutions_cache_at: 0,
  agreements: {},
  requisitions: {},
  accounts: {},
});

let _store = null;

export function load() {
  if (!existsSync(STORE_PATH)) return EMPTY();
  try {
    return JSON.parse(readFileSync(STORE_PATH, 'utf8'));
  } catch {
    return EMPTY();
  }
}

export function get() {
  if (!_store) _store = load();
  return _store;
}

export function save() {
  const dir = dirname(STORE_PATH);
  mkdirSync(dir, { recursive: true });
  writeFileSync(STORE_PATH, JSON.stringify(_store ?? EMPTY(), null, 2));
}

/** Apply a mutation function and persist immediately. */
export function update(fn) {
  const s = get();
  fn(s);
  save();
}