Exceeded Maximum Stack Depth In A Custom Function For Google Sheets

I'm creating a custom function in Google Sheets to provide the end date for a task based on the start date and the number of hours I think the task will take. i.e. end date = start

Solution 1:

Here's the working code. I ran into some serious problems whilst trying to add code to include lunchtimes, but this worked to highlight the flaws in my logic. This should now also take into account a lunchtime from a second sheet called 'Settings' in Google Sheets. (I hadn't quite worked out how to bypass the Reference error when working outside of Google Sheets). This does however solve the Exceeded maximum stack depth error. Maybe you can suggest an improvement?

 var dayStartTime = getStartTime();

 var dayEndTime = getEndTime();

 var lunchtimeEnd = getLunchtimeEnd();

 var lunchtimeStart = getLunchtimeStart();


  /* Starts the next day
   *
   * @param {number} startdate The date to add the hours to
   * @return The new date
   * @customfunction
   */

  Date.prototype.addDays = function(days) {
    var dat = new Date(this.valueOf());
    dat.setDate(dat.getDate() + days);
    return dat;
  }

  function addHours(date, h) {
     return new Date(date.getTime()  + (h*60*60*1000));
  }


    function MYWORKDAY(startdate,effort) {
    if (startdate.map) { 
      return startdate.map(MYWORKDAY); 
    } else {

      var endTime = new Date();

      var availableTimeHrs;

      var endDate = 0;

      while (effort > 0) 
      {
        endTime = new Date(startdate).setHours(dayEndTime.getHours(), dayEndTime.getMinutes(), dayEndTime.getSeconds());

        lunchtimeEnd = todaysLunchEnd(startdate);

        lunchtimeEnd = new Date(lunchtimeEnd);  

        lunchtimeStart = todaysLunchEnd(startdate);

        lunchtimeStart = new Date(lunchtimeStart);  

        endDate = addHours(startdate, effort);

        if (startdate <= lunchtimeStart && endDate >= lunchtimeEnd) {
           endDate = addHours(endDate, 1);
        } 

        if(endDate > endTime)
        {
          effort = ((Math.abs(endDate - endTime)) / 1000) / 60 / 60;   
          startdate = new Date(startdate).addDays(1);
          startdate = GetNextWorking(startdate);
          startdate = new Date(startdate).setHours(dayStartTime.getHours(), dayStartTime.getMinutes(), dayStartTime.getSeconds());
          startdate = new Date(startdate);

        } 
        else
        {
            effort = 0;
        }
      }
     }
     return endDate;
  }

  function GetNextWorking(endDate) {
     if (endDate.getDay() != 0 && endDate.getDay() != 6) {
      return endDate;
    } else {
      adjustedEndDate = new Date(endDate.setDate(endDate.getDate() + 1));
      adjustedEndDate = new Date(adjustedEndDate);
      return adjustedEndDate = GetNextWorking(adjustedEndDate);
    }
  }

  function MYSTARTDATE(startdate) {

    //var startTime = getStartTime();

    var morningStart = new Date();

    if (startdate.getHours() == 17) {
      morningStart = startdate.addDays(1);
      morningStart = GetNextWorking(morningStart);
      morningStart.setHours(9);
    } else {
      morningStart = startdate;
    }
    return morningStart;
  }

  function todaysLunchEnd(endDate) {
    var lunchtimeEnd = getLunchtimeEnd();

    lunchtimeEnd = new Date(endDate).setHours(lunchtimeEnd.getHours(), lunchtimeEnd.getMinutes(), lunchtimeEnd.getSeconds());
    lunchtimeEnd = new Date(lunchtimeEnd);
    return lunchtimeEnd;
  }

function getStartTime() {

    var settingsSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Settings");
    var range = settingsSheet.getRange("B5");
    var startTime = range.getValue(); 
    var startTime;

    if (!startTime) {
      startTime = new Date(28800000);
      //startTime = new Date(32400000); // 09:00
     }

    return startTime;
  }

  function getEndTime() {
    var settingsSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Settings");
    var range = settingsSheet.getRange("B6");
    var endTime = range.getValue(); 

    if (!endTime) {
       endTime = new Date(57600000);
       //endTime = new Date(61200000); // 17:00      
    }

    return endTime;
  }

  function getLunchtimeStart() {
    var settingsSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Settings");
    var range = settingsSheet.getRange("B7");
    var startTime = range.getValue(); 

    if (!startTime) {
      startTime = new Date(39600000); //11am
       //startTime = new Date(43200000); // 12pm
    }
    return startTime;
  }

  function getLunchtimeEnd() {
    var settingsSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Settings");
    var range = settingsSheet.getRange("B8");
    var endTime = range.getValue(); 

    if (!endTime) {
      endTime = new Date(43200000); //12:00
      //endTime = new Date(46800000); //13:00
    }

    return endTime;
  }