/*This function will test to make sure a valid
date has been entered.  If it is valid it will 
return "true".  If not, it will return "false".*/
function validateDate(month, day, year) {

   //if no year is given assume current year
   //unless date has passed, then assume next year
   if (year == null) {
      time = new Date();
      today_year = time.getYear(); 
      today_month = time.getMonth();
      today_day = time.getDay();
      if ((month > today_month) || ((month == today_month) && (day >= today_day)))
         year = today_year + 1900;
      else  year = today_year + 1901;
   }

   if ((month == null) || (day == null) || (year == null))
     return false;
   
   if (navigator.appName.indexOf("WebTV")!=-1) {
      ;//do nothing for now
   }
   else {
      var numDays;
      switch(month) {
	 case 1:
	 case 3:
	 case 5:
	 case 7:
	 case 8:
	 case 10:
	 case 12:
	    numDays = 31;
	    break;
	 case 4:
	 case 6:
	 case 9:
	 case 11:
	    numDays = 30;
	    break;
	 case 2:
	    numDays = 28;
	    break;
      }

      //Check for leap year
      if ((month == 2) && (day == 29)) {
        if (year % 100 == 0) {
          if (year % 400 != 0) 
            return false;
        }
        else {
          if (year % 4 != 0) 
            return false;
        }
      } else if (day > numDays) {
         //Compare days enter to maximum number of days in the given month
         return false;
      }

      return true;
   }
}

function validateFormDate(form_flds) {
   ix = form_flds.month.options.selectedIndex;
   ix2 = form_flds.day.options.selectedIndex;
   month = parseInt(form_flds.month.options[ix].value);
   day = parseInt(form_flds.day.options[ix2].value);

   dates_rqd = false;
   if (form_flds.dates_rqd)
      dates_rqd = form_flds.dates_rqd.value;

   if (navigator.appName.indexOf("WebTV")!=-1) {
      //do nothing for now
   }
   else {

      if (!datesCheck(month,day,dates_rqd))
        return false;

      return true;
   }

}

function validateFormDates(form_flds) {
   ix = form_flds.month.options.selectedIndex;
   ix2 = form_flds.day.options.selectedIndex;
   month = parseInt(form_flds.month.options[ix].value);
   day = parseInt(form_flds.day.options[ix2].value);
   ix = form_flds.depart_month.options.selectedIndex;
   ix2 = form_flds.depart_day.options.selectedIndex;
   depart_month = parseInt(form_flds.depart_month.options[ix].value);
   depart_day = parseInt(form_flds.depart_day.options[ix2].value);

   dates_rqd = false;
   if (form_flds.dates_rqd)
      dates_rqd = form_flds.dates_rqd.value;

   if (navigator.appName.indexOf("WebTV")!=-1) {
      //do nothing for now
   }
   else {

      if (!datesCheck(month,day,dates_rqd))
        return false;
      if (!datesCheck(depart_month,depart_day,dates_rqd))
        return false;
      if (month+day == depart_month+depart_day) {
        changeCheckOut();
      }

      return true;
   }

}

function datesCheck (month, day, dates_rqd) {

   if (dates_rqd) {
      if (day < 0 || month < 0)  {
         alert("Please enter both your Check-in AND Check-out dates");
	 return false;
      }
   }

   if ((day > 0) && (month < 0))  {
     alert("You have entered a partial date.\n"
	+ "Please enter a month or select 'Day' to clear the day.");
     return false;
   }

   if ((month > 0) && (day < 0))  {
     alert("You have entered a partial date.\n"
	+ "Please enter a day or select 'Month' to clear the month.");
     return false;
   }

   var today = new Date();
   var today_year = today.getFullYear();
   var today_month = today.getMonth();
   var today_day = today.getDay();

   var year = ((month > today_month) || ((month == today_month) 
      && (day >= today_day))) ? today_year : today_year + 1;
   
   if (!validateDate(month,day,year)) {
     alert("Invalid date:\nNot that many days in " + monthNames(month));
     return false;
   }

   return true;
}

function changeCheckOut() {
   if ((document.datesform.depart_month.selectedIndex == 0) ||
      (document.datesform.depart_month.selectedIndex < document.datesform.month.selectedIndex) ||
      ((document.datesform.depart_month.selectedIndex == document.datesform.month.selectedIndex) &&
      (document.datesform.depart_day.selectedIndex <= document.datesform.day.selectedIndex))) {
      
      if(document.datesform.month.selectedIndex != 0) {
	 if (document.datesform.month.selectedIndex == 2)  {
             var time = new Date();
             var today_year = time.getYear() + 1900; 
             var today_month = time.getMonth();
             //if the current month is past February, the following year must be assumed
             if(today_month > 2)
                today_year = today_year + 1;

             if (document.datesform.day.selectedIndex == 28 ) { 
	        if ( ( (today_year%4==0)&&(today_year%100 != 0) ) || (today_year%400==0) ) { // leap year
	           document.datesform.depart_day.selectedIndex = 29; 
                }
                else {
	          document.datesform.depart_day.selectedIndex = 1; 
	          document.datesform.depart_month.selectedIndex = 3; 
                } 
             }
             else if (document.datesform.day.selectedIndex > 28 ) { 
	       document.datesform.depart_day.selectedIndex = 1; 
	       document.datesform.depart_month.selectedIndex = 3; 
             }
             else { 
	        document.datesform.depart_day.selectedIndex = document.datesform.day.selectedIndex + 1;
	        document.datesform.depart_month.selectedIndex = document.datesform.month.selectedIndex;
             }
         }
	 else if ((document.datesform.day.selectedIndex == 30 ) &&
	    ((document.datesform.month.selectedIndex == 4) ||
	    (document.datesform.month.selectedIndex == 6)  ||
	    (document.datesform.month.selectedIndex == 9) ||
	    (document.datesform.month.selectedIndex == 11))) {
	       document.datesform.depart_day.selectedIndex = 1;
	       document.datesform.depart_month.selectedIndex = document.datesform.month.selectedIndex + 1;
	 }
         else if (document.datesform.day.selectedIndex > 30 ) {
	    document.datesform.depart_day.selectedIndex = 1;
	    if (document.datesform.month.selectedIndex == 12){ //move to January
	       document.datesform.depart_month.selectedIndex = 1;
            }
	    else  {
	       document.datesform.depart_month.selectedIndex = document.datesform.month.selectedIndex + 1;
            }
	 }
	 else {
	    document.datesform.depart_day.selectedIndex = document.datesform.day.selectedIndex + 1;
	    document.datesform.depart_month.selectedIndex = document.datesform.month.selectedIndex;
	 }
      }
   }

}

function monthNames(month) {
   var name;
   switch(month) {
      case 2:
         name = "February";
	 break;
      case 4:
         name = "April";
	 break;
      case 6:
         name = "June";
	 break;
      case 9:
         name = "September";
	 break;
      case 11:
         name = "November";
	 break;
   }
   return name;
}