/**
 * Function to stringify an Object. This Function will stringify Functions as well.
 * @param obj The Object.
 */
export function stringifyWithFunctions(obj) {
  return JSON.stringify(obj, (key, value) => {
    if (typeof value === "function") {

      let str: string = value.toString();

      // Todo Parse Arrow-Functions Correctly!
      // Details here: https://zendev.com/2018/10/01/javascript-arrow-functions-how-why-when.html
      // Difference Cases For:
      // 1) (a, b) => a + b;
      // 2) array => array[0];
      // 3) (a, b) => (a + b);
      // 4) (name, description) => ({name: name, description: description})
      // ....

      if (!str.startsWith('function') && !str.startsWith('(')) {
        const name = str.slice(0, str.indexOf('=>'));
        const func = str.slice(str.indexOf('=>(') + 3, str.length - 2)
        const adaptedFunc = 'function(' + name + '){ return ' + func + '; }';
        str = adaptedFunc;
      }

      return "/Function(" + str + ")/";
    }
    return value;
  });
}

/**
 * Function to parse a JSON String, in which methods should be available.
 * @param json A String containing the json Object
 */
export function parseWithFunctions(json: string) {
  return JSON.parse(json, (key, value) => {
    if (typeof value === "string" &&
      value.startsWith("/Function(") &&
      value.endsWith(")/")) {
      const _value = value.substring(10, value.length - 2);
      try {
        return eval("(" + _value + ")");
      } catch (e) {
        console.log('FAILED PARSING', value, _value)
      }

    }
    return value;
  });
}

/**
 * Function to stringify an Object. This Function is able to stringify Functions as well. Use the Flag withFunctions
 * @param obj The Object.
 * @param withFunctions Flag to Turn on / off the parsing of functions
 */
export function stringify(obj: any, withFunctions = false): string {
  if (withFunctions) {
    return stringifyWithFunctions(obj);
  }
  return JSON.stringify(obj);
}

/**
 * Function to parse a JSON String. This Function is able to parse Functions as well. Use the Flag withFunctions
 * @param json A String containing the json Object 
 * @param withFunctions Flag to Turn on / off the parsing of functions
 */
export function parse(json: string, withFunctions = false): any {
  if (withFunctions) {
    return parseWithFunctions(json);
  }
  return JSON.parse(json);
}