DateInput = (function ($) {
    function DateInput(el, opts) {
        if (typeof (opts) != "object") opts = {};
        $.extend(this, DateInput.DEFAULT_OPTS, opts);
        this.input = $(el);
        this.bindMethodsToObj("show", "hide", "hideIfClickOutside", "keydownHandler", "selectDate");
        this.build();
        this.selectDate();
        this.hide()
    };
    DateInput.DEFAULT_OPTS = {
        month_names: ["มกราคม", "กุมภาพันธ์", "มีนาคม", "เมษายน", "พฤษภาคม", "มิถุนายน", "กรกฎาคม", "สิงหาคม", "กันยายน", "ตุลาคม", "พฤศจิกายน", "ธันวาคม"],
        short_month_names: ["มกราคม", "กุมภาพันธ์", "มีนาคม", "เมษายน", "พฤษภาคม", "มิถุนายน", "กรกฎาคม", "สิงหาคม", "กันยายน", "ตุลาคม", "พฤศจิกายน", "ธันวาคม"],
        short_day_names: ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
        start_of_week: 0
    };
    DateInput.prototype = {
        build: function () {
            var monthNav = $('<p class="month_nav">' + '<span class="button prev" title="[Page-Up]">&#171;</span>' + ' <span class="month_name"></span> ' + '<span class="button next" title="[Page-Down]">&#187;</span>' + '</p>');
            this.monthNameSpan = $(".month_name", monthNav);
            $(".prev", monthNav).click(this.bindToObj(function () {
                this.moveMonthBy(-1)
            }));
            $(".next", monthNav).click(this.bindToObj(function () {
                this.moveMonthBy(1)
            }));
            var yearNav = $('<p class="year_nav">' + '<span class="button prev" title="[Ctrl+Page-Up]">&#171;</span>' + ' <span class="year_name"></span> ' + '<span class="button next" title="[Ctrl+Page-Down]">&#187;</span>' + '</p>');
            this.yearNameSpan = $(".year_name", yearNav);
            $(".prev", yearNav).click(this.bindToObj(function () {
                this.moveMonthBy(-12)
            }));
            $(".next", yearNav).click(this.bindToObj(function () {
                this.moveMonthBy(12)
            }));
            var nav = $('<div class="nav"></div>').append(monthNav, yearNav);
            var tableShell = "<table><thead><tr>";
            $(this.adjustDays(this.short_day_names)).each(function () {
                tableShell += "<th>" + this + "</th>"
            });
            tableShell += "</tr></thead><tbody></tbody></table>";
            this.dateSelector = this.rootLayers = $('<div class="date_selector"></div>').append(nav, tableShell).insertAfter(this.input);
            if ($.browser.msie && $.browser.version < 7) {
                this.ieframe = $('<iframe class="date_selector_ieframe" frameborder="0" src="#"></iframe>').insertBefore(this.dateSelector);
                this.rootLayers = this.rootLayers.add(this.ieframe);
                $(".button", nav).mouseover(function () {
                    $(this).addClass("hover")
                });
                $(".button", nav).mouseout(function () {
                    $(this).removeClass("hover")
                })
            };
            this.tbody = $("tbody", this.dateSelector);
            this.input.change(this.bindToObj(function () {
                this.selectDate()
            }));
            this.selectDate()
        },
        selectMonth: function (date) {
            var newMonth = new Date(date.getFullYear(), date.getMonth(), 1);
            if (!this.currentMonth || !(this.currentMonth.getFullYear() == newMonth.getFullYear() && this.currentMonth.getMonth() == newMonth.getMonth())) {
                this.currentMonth = newMonth;
                var rangeStart = this.rangeStart(date),
                    rangeEnd = this.rangeEnd(date);
                var numDays = this.daysBetween(rangeStart, rangeEnd);
                var dayCells = "";
                for (var i = 0; i <= numDays; i++) {
                    var currentDay = new Date(rangeStart.getFullYear(), rangeStart.getMonth(), rangeStart.getDate() + i, 12, 00);
                    if (this.isFirstDayOfWeek(currentDay)) dayCells += "<tr>";
                    if (currentDay.getMonth() == date.getMonth()) {
                        dayCells += '<td class="selectable_day" date="' + this.dateToString(currentDay) + '">' + currentDay.getDate() + '</td>'
                    } else {
                        dayCells += '<td class="unselected_month" date="' + this.dateToString(currentDay) + '">' + currentDay.getDate() + '</td>'
                    };
                    if (this.isLastDayOfWeek(currentDay)) dayCells += "</tr>"
                };
                this.tbody.empty().append(dayCells);
                this.monthNameSpan.empty().append(this.monthName(date));
                this.yearNameSpan.empty().append(this.currentMonth.getFullYear()+543);
                $(".selectable_day", this.tbody).click(this.bindToObj(function (event) {
                    this.changeInput($(event.target).attr("date"))
                }));
                $("td[date=" + this.dateToString(new Date()) + "]", this.tbody).addClass("today");
                $("td.selectable_day", this.tbody).mouseover(function () {
                    $(this).addClass("hover")
                });
                $("td.selectable_day", this.tbody).mouseout(function () {
                    $(this).removeClass("hover")
                })
            };
            $('.selected', this.tbody).removeClass("selected");
            $('td[date=' + this.selectedDateString + ']', this.tbody).addClass("selected")
        },
        selectDate: function (date) {
            if (typeof (date) == "undefined") {
                date = this.stringToDate(this.input.val())
            };
            if (!date) date = new Date();
            this.selectedDate = date;
            this.selectedDateString = this.dateToString(this.selectedDate);
            this.selectMonth(this.selectedDate)
        },
        changeInput: function (dateString) {
            this.input.val(dateString).change();
            this.hide()
        },
        show: function () {
            this.rootLayers.css("display", "block");
            $([window, document.body]).click(this.hideIfClickOutside);
            this.input.unbind("focus", this.show);
            $(document.body).keydown(this.keydownHandler);
            this.setPosition()
        },
        hide: function () {
            this.rootLayers.css("display", "none");
            $([window, document.body]).unbind("click", this.hideIfClickOutside);
            this.input.focus(this.show);
            $(document.body).unbind("keydown", this.keydownHandler)
        },
        hideIfClickOutside: function (event) {
            if (event.target != this.input[0] && !this.insideSelector(event)) {
                this.hide()
            }
        },
        insideSelector: function (event) {
            var offset = this.dateSelector.position();
            offset.right = offset.left + this.dateSelector.outerWidth();
            offset.bottom = offset.top + this.dateSelector.outerHeight();
            return event.pageY < offset.bottom && event.pageY > offset.top && event.pageX < offset.right && event.pageX > offset.left
        },
        keydownHandler: function (event) {
            switch (event.keyCode) {
            case 9:
            case 27:
                this.hide();
                return;
                break;
            case 13:
                this.changeInput(this.selectedDateString);
                break;
            case 33:
                this.moveDateMonthBy(event.ctrlKey ? -12 : -1);
                break;
            case 34:
                this.moveDateMonthBy(event.ctrlKey ? 12 : 1);
                break;
            case 38:
                this.moveDateBy(-7);
                break;
            case 40:
                this.moveDateBy(7);
                break;
            case 37:
                this.moveDateBy(-1);
                break;
            case 39:
                this.moveDateBy(1);
                break;
            default:
                return
            }
            event.preventDefault()
        },
        stringToDate: function (string) {
            var matches;
            if (matches = string.match(/^(\d{1,2}) ([^\s]+) (\d{4,4})$/)) {
                return new Date(matches[3]-543, this.shortMonthNum(matches[2]), matches[1], 12, 00)
            } else {
                return null
            }
        },
        dateToString: function (date) {
            return date.getDate() + " " + this.short_month_names[date.getMonth()] + " " + (date.getFullYear()+543)
        },
        setPosition: function () {
            var offset = this.input.offset();
            this.rootLayers.css({
                top: offset.top + this.input.outerHeight(),
                left: offset.left
            });
            if (this.ieframe) {
                this.ieframe.css({
                    width: this.dateSelector.outerWidth(),
                    height: this.dateSelector.outerHeight()
                })
            }
        },
        moveDateBy: function (amount) {
            var newDate = new Date(this.selectedDate.getFullYear(), this.selectedDate.getMonth(), this.selectedDate.getDate() + amount);
            this.selectDate(newDate)
        },
        moveDateMonthBy: function (amount) {
            var newDate = new Date(this.selectedDate.getFullYear(), this.selectedDate.getMonth() + amount, this.selectedDate.getDate());
            if (newDate.getMonth() == this.selectedDate.getMonth() + amount + 1) {
                newDate.setDate(0)
            };
            this.selectDate(newDate)
        },
        moveMonthBy: function (amount) {
            var newMonth = new Date(this.currentMonth.getFullYear(), this.currentMonth.getMonth() + amount, this.currentMonth.getDate());
            this.selectMonth(newMonth)
        },
        monthName: function (date) {
            return this.month_names[date.getMonth()]
        },
        bindToObj: function (fn) {
            var self = this;
            return function () {
                return fn.apply(self, arguments)
            }
        },
        bindMethodsToObj: function () {
            for (var i = 0; i < arguments.length; i++) {
                this[arguments[i]] = this.bindToObj(this[arguments[i]])
            }
        },
        indexFor: function (array, value) {
            for (var i = 0; i < array.length; i++) {
                if (value == array[i]) return i
            }
        },
        monthNum: function (month_name) {
            return this.indexFor(this.month_names, month_name)
        },
        shortMonthNum: function (month_name) {
            return this.indexFor(this.short_month_names, month_name)
        },
        shortDayNum: function (day_name) {
            return this.indexFor(this.short_day_names, day_name)
        },
        daysBetween: function (start, end) {
            start = Date.UTC(start.getFullYear(), start.getMonth(), start.getDate());
            end = Date.UTC(end.getFullYear(), end.getMonth(), end.getDate());
            return (end - start) / 86400000
        },
        changeDayTo: function (dayOfWeek, date, direction) {
            var difference = direction * (Math.abs(date.getDay() - dayOfWeek - (direction * 7)) % 7);
            return new Date(date.getFullYear(), date.getMonth(), date.getDate() + difference)
        },
        rangeStart: function (date) {
            return this.changeDayTo(this.start_of_week, new Date(date.getFullYear(), date.getMonth()), -1)
        },
        rangeEnd: function (date) {
            return this.changeDayTo((this.start_of_week - 1) % 7, new Date(date.getFullYear(), date.getMonth() + 1, 0), 1)
        },
        isFirstDayOfWeek: function (date) {
            return date.getDay() == this.start_of_week
        },
        isLastDayOfWeek: function (date) {
            return date.getDay() == (this.start_of_week - 1) % 7
        },
        adjustDays: function (days) {
            var newDays = [];
            for (var i = 0; i < days.length; i++) {
                newDays[i] = days[(i + this.start_of_week) % 7]
            };
            return newDays
        }
    };
    $.fn.date_input = function (opts) {
        return this.each(function () {
            new DateInput(this, opts)
        })
    };
    $.date_input = {
        initialize: function (opts) {
            $("input.date_input").date_input(opts)
        }
    };
    return DateInput
})(jQuery);