// Tiny JSON store on the volume. Every collection is one file; writes are atomic (tmp + rename).
// PolHunter's data is small (missions, completions, payouts) and a member's balance never lives
// here, so a database would be ceremony. If it ever grows, this is the one file to swap.
'use strict';
const fs = require('fs');
const path = require('path');

let DIR = null;
function init(dir) { DIR = dir; fs.mkdirSync(DIR, { recursive: true }); }
const file = name => path.join(DIR, name + '.json');

function read(name, fallback) {
  try { return JSON.parse(fs.readFileSync(file(name), 'utf8')); } catch (e) { return fallback; }
}
function write(name, data) {
  const f = file(name), tmp = f + '.tmp';
  fs.writeFileSync(tmp, JSON.stringify(data));
  fs.renameSync(tmp, f);
}
// read-modify-write in one place so callers never race themselves
function update(name, fallback, fn) {
  const cur = read(name, fallback);
  const out = fn(cur) || cur;
  write(name, out);
  return out;
}

module.exports = { init, read, write, update };