const { dialog } = require('electron');
const { homedir } = require('os');
const { resolve } = require('path');
const { readFileSync, writeFileSync } = require('fs');
const gaze = require('gaze');
const vm = require('vm');

const path = resolve(homedir(), '.hyperterm.js');
const watchers = [];

let cfg = {};

function watch () {
  gaze(path, function (err) {
    if (err) throw err;
    this.on('changed', () => {
      try {
        if (exec(readFileSync(path, 'utf8'))) {
          watchers.forEach((fn) => fn());
        }
      } catch (err) {
        dialog.showMessageBox({
          message: `An error occurred loading your configuration (${path}): ${err.message}`,
          buttons: ['Ok']
        });
      }
    });
  });
}

let _str; // last script
function exec (str) {
  if (str === _str) return false;
  _str = str;
  const script = new vm.Script(str);
  const module = {};
  script.runInNewContext({ module });
  if (!module.exports) {
    throw new Error('Error reading configuration: `module.exports` not set');
  }
  const _cfg = module.exports.config;
  if (!_cfg) {
    throw new Error('Error reading configuration: `config` key is missing');
  }
  cfg = _cfg;
  return true;
}

exports.subscribe = function (fn) {
  watchers.push(fn);
  return () => {
    watchers.splice(watchers.indexOf(fn), 1);
  };
};

exports.init = function () {
  try {
    exec(readFileSync(path, 'utf8'));
  } catch (err) {
    console.log('read error', path, err.message);
    const defaultConfig = readFileSync(resolve(__dirname, 'config-default.js'));
    try {
      console.log('attempting to write default config to', path);
      exec(defaultConfig);
      writeFileSync(path, defaultConfig);
    } catch (err) {
      throw new Error(`Failed to write config to ${path}`);
    }
  }
  watch();
};

exports.get = function () {
  return cfg;
};