'use strict';
const fs = require('fs');
const path = require('path');
const { EventEmitter } = require('events');

const CONFIG_PATH = process.env.MYPRIMAL_CONFIG_PATH || path.join(__dirname, '..', 'config.json');

const DEFAULTS = {
  poll: {
    fast:      parseInt(process.env.POLL_FAST)   || 60,
    normal:    parseInt(process.env.POLL_NORMAL) || 300,
    slow:      parseInt(process.env.POLL_SLOW)   || 900,
    overrides: {},
  },
  expressions: {},  // inputId → expression string override, e.g. "value/10"
};

const emitter = new EventEmitter();
let _config = deepMerge({}, DEFAULTS);

function deepMerge(target, source) {
  for (const key of Object.keys(source || {})) {
    if (source[key] && typeof source[key] === 'object' && !Array.isArray(source[key])) {
      target[key] = deepMerge(target[key] || {}, source[key]);
    } else {
      target[key] = source[key];
    }
  }
  return target;
}

function loadConfig() {
  if (fs.existsSync(CONFIG_PATH)) {
    try {
      const saved = JSON.parse(fs.readFileSync(CONFIG_PATH, 'utf8'));
      _config = deepMerge(deepMerge({}, DEFAULTS), saved);
    } catch (e) {
      console.warn('[config] Failed to parse config.json, using defaults:', e.message);
    }
  }
}

function saveConfig() {
  fs.writeFileSync(CONFIG_PATH, JSON.stringify(_config, null, 2));
}

function getConfig() {
  return _config;
}

function patchConfig(patch) {
  _config = deepMerge(_config, patch);
  saveConfig();
  emitter.emit('change', _config);
}

module.exports = { loadConfig, getConfig, patchConfig, on: emitter.on.bind(emitter) };