//  VALIDATE E-MAIL ADDRESSES
function IsValidEmail(str) {
    if (str == '') return true;

    var at = "@"
    var dot = "."
    var lat = str.indexOf(at)
    var lstr = str.length
    var ldot = str.indexOf(dot)
    if (str.indexOf(at) == -1) {
        return false
    }

    if (str.indexOf(at) == -1 || str.indexOf(at) == 0 || str.indexOf(at) == lstr) {
        return false
    }

    if (str.indexOf(dot) == -1 || str.indexOf(dot) == 0 || str.indexOf(dot) == lstr) {
        return false
    }

    if (str.indexOf(at, (lat + 1)) != -1) {
        return false
    }

    if (str.substring(lat - 1, lat) == dot || str.substring(lat + 1, lat + 2) == dot) {
        return false
    }

    if (str.indexOf(dot, (lat + 2)) == -1) {
        return false
    }

    if (str.indexOf(" ") != -1) {
        return false
    }

    return true
}


//  VALIDATE DATES


/**
* DHTML date validation script
*/
// Declaring valid date character, minimum year and maximum year
var dtCh = "/";
var minYear = 2000;
var maxYear = 2100;

function isInteger(s) {
    var i;
    for (i = 0; i < s.length; i++) {
        // Check that current character is number.
        var c = s.charAt(i);
        if (((c < "0") || (c > "9")))
            return false;
    }
    // All characters are numbers.
    return true;
}

function stripCharsInBag(s, bag) {
    var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++) {
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

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 isLeapYear(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)));
}

function DaysArray(n) {
    for (var i = 1; i <= n; i++) {
        this[i] = 31;
        if (i == 4 || i == 6 || i == 9 || i == 11) {
            this[i] = 30;
        }
        if (i == 2) {
            this[i] = 29;
        }
    }
    return this;
}

function IsValidStartEndDates(dtStartStr, dtEndStr, checkEmpty) {

    if ((!IsDate(dtStartStr) || !IsDate(dtEndStr))) {
        return false;
    }
    
    if (dtStartStr == '' && dtEndStr == '' && !checkEmpty) return true;
    if (dtStartStr == '' || dtEndStr == '') {
        if (checkEmpty) {
            alert('Both dates must be provided');
            return false;
        } else {
            alert('Both or neither dates must be provided');
            return false;
        }
    }

    var pos1 = dtStartStr.indexOf(dtCh);
    var pos2 = dtStartStr.indexOf(dtCh, pos1 + 1);
    var startDay = parseInt(dtStartStr.substring(0, pos1), 10);
    var startMonth = parseInt(dtStartStr.substring(pos1 + 1, pos2), 10);
    var startYear = parseInt(dtStartStr.substring(pos2 + 1), 10);

    pos1 = dtEndStr.indexOf(dtCh);
    pos2 = dtEndStr.indexOf(dtCh, pos1 + 1);
    var endDay = parseInt(dtEndStr.substring(0, pos1), 10);
    var endMonth = parseInt(dtEndStr.substring(pos1 + 1, pos2), 10);
    var endYear = parseInt(dtEndStr.substring(pos2 + 1), 10);

    if (endYear > startYear) {
        return true;
    } else if (endYear < startYear) {
        alert("The End Date is before the Start Date");
        return false;
    }
    if (endYear == startYear) {
        if (endMonth > startMonth) {
            return true;
        } else if (endMonth < startMonth) {
            alert("The End Date is before the Start Date");
            return false;
        }

        if (endMonth == startMonth) {
            if (endDay >= startDay) {
                return true;
            } else if (endDay < startDay) {
                alert("The End Date is before the Start Date");
                return false;
            }
       }
    }
    return false;
}
function IsDate(dtStr) {
    if (dtStr == '') return true;
    var daysInMonth = DaysArray(12);
    var pos1 = dtStr.indexOf(dtCh);
    var pos2 = dtStr.indexOf(dtCh, pos1 + 1);
    var strDay = dtStr.substring(0, pos1);
    var strMonth = dtStr.substring(pos1 + 1, pos2);
    var strYear = dtStr.substring(pos2 + 1);
    strYr = strYear;
    if (strDay.charAt(0) == "0" && strDay.length > 1) strDay = strDay.substring(1);
    if (strMonth.charAt(0) == "0" && strMonth.length > 1) strMonth = strMonth.substring(1);
    for (var i = 1; i <= 3; i++) {
        if (strYr.charAt(0) == "0" && strYr.length > 1) strYr = strYr.substring(1);
    }
    month = parseInt(strMonth);
    day = parseInt(strDay);
    year = parseInt(strYr);
    if (pos1 == -1 || pos2 == -1) {
        alert("The date format should be : dd/mm/yyyy");
        return false;
    }
    if (strMonth.length < 1 || month < 1 || month > 12) {
        alert("Please enter a valid month");
        return false;
    }
    if (strDay.length < 1 || day < 1 || day > 31 || (month == 2 && day > daysInFebruary(year)) || day > daysInMonth[month]) {
        alert("Please enter a valid day");
        return false;
    }
    if (strYear.length != 4 || year == 0 || year < minYear || year > maxYear) {
        alert("Please enter a valid 4 digit year between");
        return false;
    }
    if (dtStr.indexOf(dtCh, pos2 + 1) != -1 || isInteger(stripCharsInBag(dtStr, dtCh)) == false) {
        alert("Please enter a valid date");
        return false;
    }
    return true
}