(function ($) {
    function compareDates(start, end, format) {
        var temp, dateStart, dateEnd;
        try {
            dateStart = $.datepicker.parseDate(format, start);
            dateEnd = $.datepicker.parseDate(format, end);
            if (dateEnd < dateStart) {
                temp = start;
                start = end;
                end = temp;
            }
        } catch (ex) {}

        return { start: start, end: end };
    }

    $.fn.daterange = function (opts) {
        // defaults
        opts = $.extend({
          "changeMonth": false,
          "changeYear": false,
          "numberOfMonths": 3
        }, opts || {});

        var onSelect = opts.onSelect || $.noop;
        var onClose = opts.onClose || $.noop;
        var beforeShow = opts.beforeShow || $.noop;
        var beforeShowDay = opts.beforeShowDay;

        var lastDateRange;
        
        function checkDate(strDate){
            if(!strDate.match(/^\d{4}\/\d{1,2}\/\d{1,2}$/)){
                return false;
            }
            var dateArr = strDate.split("/");
            if(dateArr.length < 3){
                return false;
            }
            var year = Number(dateArr[0]);
            var month = Number(dateArr[1] - 1);
            var day = Number(dateArr[2]);

            if(year >= 0 && month >= 0 && month <= 11 && day >= 1 && day <= 31){
                var date = new Date(year, month, day);
                if(isNaN(date)){
                    return false;
                }else if(date.getFullYear() == year && date.getMonth() == month && date.getDate() == day){
                    return true;
                }
            }
            return false;
        }
        
        function storeLastDateRange(fromdateText, todateText, dateFormat) {
            var start, end;
            
            if ( fromdateText != "" && todateText != "" ){
                start = $.datepicker.parseDate(dateFormat, fromdateText);
                  end = $.datepicker.parseDate(dateFormat, todateText);
                  lastDateRange = {start: start, end: end};
            } else {
                lastDateRange = null;
            }
        }

        opts.beforeShow = function (input, inst) {
            var elemntDatepicker =  document.getElementById("datepicker_from");
            var fromdatevalue = elemntDatepicker.value;
            if ( !checkDate(fromdatevalue) ){
                fromdatevalue = "";
            }
            var elemntDatepicker =  document.getElementById("datepicker_to");
            var todatevalue = elemntDatepicker.value;
            if ( !checkDate(todatevalue) ){
                todatevalue = "";
            }
            $(this).datepicker('setDate' , fromdatevalue);
            
            var dateFormat = $(this).datepicker("option", "dateFormat");
            storeLastDateRange(fromdatevalue, todatevalue, dateFormat);
            beforeShow.apply(this, arguments);
        };

        opts.beforeShowDay = function (date) {
            var out = [true, ""], extraOut;
            if (lastDateRange && lastDateRange.start <= date) {
                if (lastDateRange.end && date <= lastDateRange.end) {
                    out[1] = "ui-datepicker-range";
                }
            }
            if (beforeShowDay) {
              extraOut = beforeShowDay.apply(this, arguments);
              out[0] = out[0] && extraOut[0];
              out[1] = out[1] + " " + extraOut[1];
              out[2] = extraOut[2];
            }
            return out;
        };

        // datepicker's select date event handler
        opts.onSelect = function (dateText, inst) {
            var textStart;
            if (!inst.rangeStart) {
                inst.inline = true;
                inst.rangeStart = dateText;
                
                var elemntFrom = document.getElementById("datepicker_from");
                elemntFrom.value = dateText;
                SelectChangeDatepicker('datepicker_from', 'srch_syear', 'srch_smonth', 'srch_sday');
                
                var elemntTo = document.getElementById("datepicker_to");
                elemntTo.value = dateText;
                SelectChangeDatepicker('datepicker_to', 'srch_eyear', 'srch_emonth', 'srch_eday');
            } else {
                inst.inline = false;
                textStart = inst.rangeStart;
                if (textStart !== dateText) {
                    var dateFormat = $(this).datepicker("option", "dateFormat");
                    var dateRange = compareDates(textStart, dateText, dateFormat);
                    $(this).val(dateRange.end);
                    //$(this).val(dateRange.start + opts.rangeSeparator + dateRange.end);
                    inst.rangeStart = null;
                    
                    var elemntFrom = document.getElementById("datepicker_from");
                    elemntFrom.value = dateRange.start;
                    SelectChangeDatepicker('datepicker_from', 'srch_syear', 'srch_smonth', 'srch_sday');
                    
                    var elemntTo = document.getElementById("datepicker_to");
                    elemntTo.value = dateRange.end;
                    SelectChangeDatepicker('datepicker_to', 'srch_eyear', 'srch_emonth', 'srch_eday');
                }
            }
            // call original callback for select event
            onSelect.apply(this, arguments);
        };

        opts.onClose = function (dateText, inst) {
            // reset state
            inst.rangeStart = null;
            inst.inline = false;
            // call original callback for close event
            onClose.apply(this, arguments);
        };

        return this.each(function () {
            var input = $(this);
            if (input.is("input")) {
              input.datepicker(opts);
            }
        });
    };
}(jQuery));