/**
 * Check parameter 
  1. Parameter über externe Funktion prüfen, um Code nicht zu wiederholen.
  2. Script soll manchmal abgebrochen werden, wenn es Parameter Fehler gab.
  3. Methode soll true/false als Feedback zurückgeben, um darauf reagieren zu können.
  4. Alle Fehler erhalten und wissen welcher Parameter Fehler enthält.
  5. In der Konsole alle Fehler sehen.
 */

const parameterCheck = {
/** 
 * Get final result for all checks. An object if there were errors (one object in the array) and null if no errors 
 */
  result: function (arrCheck){
    /** Filter objects in the array arrCheck */
    const arrResult = arrCheck.map(arr => arr.filter(item => typeof item === 'object' && item instanceof Array  === false));
    /** Create message for all errors */
    let n = 1;
    const arrAllMessages = 
      arrResult.map(parameterErrors => '\n' + n++ + '. parameter - errors:\n' + parameterErrors.map(error => '- '+error.message+'\n').join('')).join('');
    
    /** If arrResult contains an element it shows that one error object was added to arrCheck */
    if(arrResult.some(item => item.length)){
      return {
        /** Return the final status for all checks */
        status: false,
        /** Return the array which contains only the error objects */
        errors: arrResult,
        /** message for all errors */
        message: arrAllMessages
      }
    }      
    /** If no errors return null */
    else{
      return null;
    }
  },
/** 
 * Check functions
 */  
  /** is an array */ 
  typeArray: function(arr){  
    if(!Array.isArray(arr)){
      return {
        name: 'typeArray',
        message: 'Must be an array!'
      }
    }      
  },
  /** string or array is not empty */ 
  filled: function(val){     
    if(!val.length){
      return {
        name: 'filled',
        message: 'Element is empty!'
      }
    }    
  },
  /** String? */
  typeString: function(str){    
    if(typeof str !== 'string'){
      return {
        name: 'typeString',
        message: 'Must be a string!'
      }
    }     
  },
  /** Integer? */
  typeInt: function(int){   
    if(!Number.isInteger(int)){
      return {
        name: 'typeInt',
        message: 'Must be an integer!'
      }
    }     
  }
}
  
/****
 * Classes
 ****/
  class Data{
    
    /** Method */
    createList(arr,str){
       /**
        * Check parameters. First element = 1st parameter, 2nd element = 2nd parameter and so on.  
        */   
         let arrCheck = [
           [
             parameterCheck.typeArray(arr),
             parameterCheck.filled(arr),
           ],
           [
             parameterCheck.typeString(str)
           ]     
         ]

        /** 
         * Get the final result for the parameter check. if not null there were errors.
         * Paramter error(s). return stop also the code here.
         */
          let errors = parameterCheck.result(arrCheck);
          if(errors !== null){
           /** returns an object with the final status for all checks and the array which contains the error objects */
           return errors  // {status:false,errors:array,message:str}
          }
      /***** Parameter check end *****/

      /** 
       * Paramter(s) are fine. Execute the method script and return the final status for this method and response.
       */    
        let arrLi = arr.map(item => `<li>${item}</li>`);
        return {
          status: true,
          response: arrLi
        }
    }
  }

/****
 * Script
 ****/

  /** Array */
  const arrMovies = [
    'Batman Begins',
    'Prometheus',
    'I Am Legend'
  ];
  
  /** Objekt der Klasse Data erzeugen */
  const movies = new Data();
  
  /** Call method */
  // const methodResponse = movies.createList(arrMovies,3);         // status: false
  const methodResponse = movies.createList('',2);                   // status: false
  // const methodResponse = movies.createList(2,'Movies');          // status: false
  // const methodResponse = movies.createList(arrMovies,'Movies');  // status: true

  /** Log the result object of checked parameters */
  console.log('result: ', methodResponse);

  /**
   * Get errors
   */
    if(methodResponse.status === false){
      
      /** do something, because the method has errors */
      console.log('do something, because the method has errors');
      
      /** 
       * check which Parameter has errors 
       */
        /** 1st parameter has errors...do something */
        if(methodResponse.errors[0].length){
          console.log('1st parameter has errors...do something');
        }
        /** 2nd parameter has errors...do something */
        if(methodResponse.errors[1].length){
          console.log('2nd parameter has errors...do something');
        }
      
      /** 
       * Throw error 
       */      
        throw new Error(methodResponse.message);
      
    }