// This is JavaScript, but we may do PHP things here in future... (Check referrer for instance)

  // These JavaScript checks are copyright Whizzart Image & Interaction 2000-2001
  // Arnoud van Delden - http://www.whizzart.nl or http://www.whizzweb.nl

  var MayBeEmpty = false;
  var MayNotBeEmpty = true;
  var DefaultEmptyOK = false;

  function IsMonth(s) {
    if (IsEmpty(s))
      if (IsMonth.arguments.length == 1) return DefaultEmptyOK;
    else return (IsMonth.arguments[1] == true);
    return IsIntegerInRange (s, 1, 12);
  }

  function IsYear(s) {
    if (IsEmpty(s))
      if (IsYear.arguments.length == 1) return DefaultEmptyOK;
    else return (IsYear.arguments[1] == true);
    if (!IsNonNegativeInteger(s)) return false;
    return ((s.length == 2) || (s.length == 4));
  }

  function IsDay(s) {
    if (IsEmpty(s))
    if (IsDay.arguments.length == 1) return DefaultEmptyOK;
      else return (IsDay.arguments[1] == true);
    return IsIntegerInRange (s, 1, 31);
  }

  function DaysInFebruary(Year) {
    // February has 29 days in any year evenly divisible by four,
    // EXCEPT for centurial years which are not also divisible by 400.
    return (((Year % 4 == 0) && ((!(Year % 100 == 0)) || (Year % 400 == 0))) ? 29 : 28);
  }

  function IsDate(Year, Month, Day) {
    var DaysInMonth = new Array('31','29','31','30','31','30','31','31','30','31','30','31');
    // catch invalid years (not 2- or 4-digit) and invalid months and days.
    if (! (IsYear(Year, false) && IsMonth(Month, false) && IsDay(Day, false))) return false;
    // Explicitly change type to integer to make code work in both
    // JavaScript 1.1 and JavaScript 1.2.
    var IntYear = parseInt(Year);
    var IntMonth = parseInt(Month);
    var IntDay = parseInt(Day);

    // catch invalid days, except for February
    if (IntDay > DaysInMonth[IntMonth-1]) return false;
    if ((IntMonth == 2) && (IntDay > DaysInFebruary(IntYear))) {
      alert("Februari heeft " + DaysInFebruary(IntYear) + " dagen voor het opgegeven jaar.")
      return false;
    }
    return true;
  }

  // NotNumeric is used by IsStringDate, returns true if not numeric...
  function NotNumeric(s) {
    var i;
    for (i = 0; i < s.length; i++) {
      var c = s.charAt(i);
      if ((c < "0") || (c > "9")) return true;
    }
    return false;
  }

  function IsStringDate(args) {
    // Args: Date, Required_Y/N, FieldDescr, [StartDay]
    var Field = arguments[0];
    var IsRequired = arguments[1];
    var FieldDescription = arguments[2];

    // Be more tolerant (11-4-2001)...
    var CheckStr = Field.value;
    if (IsRequired!=true && CheckStr=='') return true;
    CheckStr = CheckStr.replace(/\/+/gi,'-');
    CheckStr = CheckStr.replace(/\ +/gi,'-');
    var Parts = CheckStr.split('-');

    // Check if three parts where given (5-9-2001)...
    if (Parts.length != 3) {
      alert(FieldDescription + ": Geef drie door streepjes of spaties gescheiden\n"
                             + "nummerieke delen op voor resp. dag, maand en jaar. Een\n"
                             + "dagaanduiding (bv. donderdag) is niet nodig.");
      if (Field.type != 'hidden') Field.focus();
      return false;
    }

    // Check if the parts are numeric (5-9-2001)...
    if (NotNumeric(Parts[0]) || NotNumeric(Parts[1]) || NotNumeric(Parts[2])) {
      alert(FieldDescription + ": Geef drie door streepjes of spaties gescheiden\n"
                             + "nummerieke delen op voor resp. dag, maand en jaar.\n"
                             + "Gebruik alleen getallen, geen letters.");
      if (Field.type != 'hidden') Field.focus();
      return false;
    }

    if (eval(Parts[0]) < 10) Parts[0] = "0"+eval(Parts[0]);
    if (eval(Parts[1]) < 10) Parts[1] = "0"+eval(Parts[1]);
    TempYear = eval(Parts[2]);
    if (TempYear < 100)
      if (TempYear > 40) TempYear = TempYear+1900; else TempYear = TempYear+2000;
    if (Field.value) Field.value = Parts[0]+"-"+Parts[1]+"-"+TempYear;

    var Re = /\d\d\-\d\d\-\d\d\d\d/;
    var RetVal = false;
    if (Field.value == null || Field.value == "") {
      if (IsRequired == true) {
        alert("Het veld " + FieldDescription.toLowerCase() + " is verplicht.");
        if (Field.type != 'hidden') Field.focus();
      } else RetVal = true;
    } else {
      if(!Re.test(Field.value)) {
        alert(FieldDescription + ": gebruik altijd twee cijfers voor de dag- en de\n"
              + "maandaanduiding en vier voor de jaaraanduiding.\n\n"
              + "Bijvoorbeeld: 31 januari 2003 wordt 31-01-2003.");
        if (Field.type != 'hidden') Field.focus();
      } else {
        var Year  = Field.value.substring(6,10);
        var Month = Field.value.substring(3,5);
        var Day   = Field.value.substring(0,2);
        if (!IsDate(Year, Month, Day)) {
          alert(FieldDescription + ": ongeldige datum (" + Day + "-" + Month + "-" + Year + ")");
        } else {
          if (IsStringDate.arguments.length == 4) {
            var RequiredDayOfTheMonthValue = IsStringDate.arguments[3];
            if(RequiredDayOfTheMonthValue != Day) {
              alert(FieldDescription + ": deze moet beginnen op dag "
                    + RequiredDayOfTheMonthValue + " van de maand.\n\nIn uw geval dus: "
                    + RequiredDayOfTheMonthValue + "-" + Month + "-" + Year + ".");
            } else RetVal = true;
          } else RetVal = true;
        }
      }
    }
    return RetVal;
  }

  function CheckDateRange(StartDate, EndDate, Message) {
    if (IsEmpty(EndDate)  && !IsEmpty(StartDate)) return true;
    if (IsEmpty(EndDate)  && IsEmpty(StartDate)) return true;
    if (!IsEmpty(EndDate) && IsEmpty(StartDate))
    {
      alert("Er kan geen einddatum zijn zonder een aanvangsdatum.\n" + Message);
      return false;
    }
    var RetVal = false;
    if (IsStringDate(StartDate) && IsStringDate(EndDate)) {
      YearStart  = StartDate.substring(6,10);
      MonthStart = StartDate.substring(3,5);
      DayStart   = StartDate.substring(0,2);
      YearEnd    = EndDate.substring(6,10);
      MonthEnd   = EndDate.substring(3,5);
      DayEnd     = EndDate.substring(0,2);

      if (YearStart < YearEnd) RetVal = true;
      else {
        if (YearStart == YearEnd) {
          if (MonthStart < MonthEnd) RetVal = true;
          else {
            if (MonthStart == MonthEnd) {
              if (DayStart <= DayEnd) RetVal = true;
            }
          }
          if(!RetVal) alert("De chronologische volgorde van de datumvelden klopt niet.\n" + Message);
        }
      }
    }
    return RetVal;
  }

  function CalcDuration(StartDate, EndDate, Units, Message) {
    var Duration = 0;
    if (CheckDateRange(StartDate, EndDate, Message)) {
      DurationYears = 0;
      DurationMonths = 0;
      YearStart  = StartDate.substring(6,10);
      MonthStart = StartDate.substring(3,5);
      DayStart   = StartDate.substring(0,2);
      YearEnd    = EndDate.substring(6,10);
      MonthEnd   = EndDate.substring(3,5);
      DayEnd     = EndDate.substring(0,2);
      DurationYears = YearEnd - YearStart;
      DurationMonths = MonthEnd - MonthStart;

      if (Units == "maanden") {
        DurationYearsInMonths = 12 * DurationYears;
        Duration = DurationYearsInMonths + DurationMonths;
      } else {
        if (Units != "jaren") {
          alert("De opgegeven eenheid voor het berekenen van de duur: "
               + Units + " wordt niet herkend.\n"
               + "De functie zal 'jaren' hiervoor gebruiken");
        }
        Units = "jaren";
        if (YearStart <= YearEnd) {
          Duration = DurationYears;
          if (MonthStart > MonthEnd) {
            Duration = Duration - 1;
          }
          if (MonthStart == MonthEnd) {
            if(DayStart > DayEnd) {
              Duration = Duration - 1;
            }
          }
        }
      }
    }
    return Duration;
  }

  function CalcEndDate(StartDate, Duration, Units) {
    var EndDate = "";
    var IntDuration = 0;
    IntDuration = parseInt(Duration);
    var Year = 0;
    var FloatYear = 0;
    var IntYear = 0;
    var Month = 0;
    var Day = 0;
    if (Duration != null && Duration != "") IntDuration = parseInt(Duration);
    if (IsStringDate(StartDate)) {
      Year  = parseFloat(StartDate.substring(6,10));
      Month = parseFloat(StartDate.substring(3,5));
      Day   = parseFloat(StartDate.substring(0,2));
      if (Units == "maanden") {
        Month = Month + IntDuration%12;
        FloatYear = Year + IntDuration/12;
        Year = Math.floor(FloatYear);
        if (Month > 11) {
          var FloatYear = Year + Month/12;
          Year = Math.floor(FloatYear);
          Month = Month%12;
        }
      } else {
        if (Units != "jaren") {
          alert("De opgegeven eenheid voor het berekenen van de duur: " + Units + " wordt niet herkend.\n"
                 + "De functie zal uit gaan van 'jaren'");
          Units = "jaren";
        }
        Year = Year + IntDuration;
      }
      if (Day > 0 && Day < 10) { EndDate = "0" + Day.toString(); }
      else { EndDate = Day.toString(); }
      EndDate = EndDate + "-";
      if (Month > 0 && Month < 10) { EndDate = EndDate + "0" + Month.toString(); }
      else { EndDate = EndDate + Month.toString(); }
      EndDate = EndDate + "-" + Year.toString();
    }
    return EndDate;
  }

  function Today(Field) {
     var Today = new Date();
     var yy = Today.getYear();
     var Year = (yy < 1000) ? yy + 1900 : yy;
     Day = Today.getDate();
     if (Day<10) Day = "0" + Day;
     Month = Today.getMonth() + 1;
     if (Month<10) Month = "0" + Month;
     Field.value = Day + "-" + Month + "-" + Year;
  }

  function ThisMoment(Field) {
     // Returns mySql compliant DATETIME format...
     var Today = new Date();
     var yy = Today.getYear();
     var Year = (yy < 1000) ? yy + 1900 : yy;
     Day = Today.getDate();
     if (Day<10) Day = "0" + Day;
     Month = Today.getMonth() + 1;
     if (Month<10) Month = "0" + Month;
     var Hours = Today.getHours();
     if (Hours<10) Hours = "0" + Hours;
     var Minutes = Today.getMinutes();
     if (Minutes<10) Minutes = "0" + Minutes;
     var Seconds = Today.getSeconds();
     if (Seconds<10) Seconds = "0" + Seconds;
     Field.value = Year+"-"+Month+"-"+Day+" "+Hours+":"+Minutes+":"+Seconds;
  }