const { readdir } = require('fs');
const { join, resolve } = require('path');

const internals = {

  dates: [
    'today',
    'tomorrow',
    'next friday',
    'next wednesday',
    'last thursday',
    'last tuesday',
    'the next day divisible by 7',
    'this afternoon',
    'next fiscal quarter',
  ],

  rules: null,
  currentIndex: 0,

  kRulesDirectory: resolve(__dirname, './rules'),

  async readRules() {

    const ruleFiles = await internals.readdir(internals.kRulesDirectory);
    const rules = ruleFiles
      .filter((file) => file.match(/.js$/))
      .map((file) => require(join(internals.kRulesDirectory, file)));

    internals.rules = rules.sort(() => Math.random() - 0.5)
  },

  readdir(path) {
    return new Promise((resolve, reject) => {

      readdir(path, (err, files) => {

        if (err) {
          return reject(err);
        }

        return resolve(files);
      })
    });
  }
}

module.exports = {
  async generate() {

    if (!internals.rules) {
      await internals.readRules();
    }

    const rule = internals.rules[internals.currentIndex];
    const time = internals.dates[Math.floor(Math.random() * internals.dates.length)];
    internals.currentIndex = (internals.currentIndex + 1) % internals.rules.length
    return {
      rule: rule(),
      time
    }
  }
}