const path = require('path');
const Field = require('./field.js');

let instance = null;

class Config {
   constructor() {
      this.location = Config.determineLocation();
      this.fields = require(`${this.location}`);
   }

   static getInstance() {
      if (instance == null) {
         instance = new Config();
      }
      return instance;
   }

   static determineLocation() {
      return path.join(__dirname, '..', '..', process.env.SEASONED_CONFIG);
   }

   get(section, option) {
      if (this.fields[section] === undefined || this.fields[section][option] === undefined) {
         throw new Error(`Filed "${section} => ${option}" does not exist.`);
      }

      const field = new Field(this.fields[section][option]);

      if (field.value === '') {
         const envField = process.env[['SEASONED', section.toUpperCase(), option.toUpperCase()].join('_')];
         if (envField !== undefined && envField.length !== 0) { return envField; }
      }

      if (field.value === undefined) {
         throw new Error(`${section} => ${option} is empty.`);
      }

      return field.value;
   }
}

module.exports = Config;