(function($) {
    var monthNames = ['January', 'February', 'March', 'April', 'May', 'June',
        'July', 'August', 'September', 'October', 'November', 'December'];

    function createDate(year, month, day)
    {
        var date = new Date();
        date.setFullYear(year);
        date.setMonth(month || 0);
        date.setDate(day || 1);
        return date;
    }

    function getToday()
    {
        return new Date();
    }

    function areDatesEqual(date1, date2)
    {
        return String(date1) == String(date2);
    }

    function daysInMonth(year, month)
    {
        if (year instanceof Date) return daysInMonth(year.getFullYear(), year.getMonth());
        if (month == 1) {
            var leapYear = (year % 4 == 0) &&
                (!(year % 100 == 0) || (year % 400 == 0));
            return leapYear ? 29 : 28;
        } else if (month == 3 || month == 5 || month == 8 || month == 10) {
            return 30;
        } else {
            return 31;
        }
    }

    function dayAfter(date)
    {
        return createDate(date.getFullYear(), date.getMonth(), date.getDate()+1);
    }

    function dayBefore(date)
    {
        return createDate(date.getFullYear(), date.getMonth(), date.getDate()-1);
    }

    function monthAfter(year, month)
    {
        return createDate(year, month + 1);
    }

    function formatDate(date, options)
    {
        options = options || {};
        options.separator = options.separator || '/';

        var s;
        if (options.iso) {
            var m = date.getMonth() + 1;
            var d = date.getDate();
            return date.getFullYear() + '-' + (m < 10 ? '0'+m : m) + '-' + (d < 10 ? '0'+d : d);
        }
        if (options.usa) {
            s = (date.getMonth() + 1) + options.separator + date.getDate()
        } else {
            s = date.getDate() + options.separator + (date.getMonth() + 1)
        }
        return s + options.separator + date.getFullYear();
    }

    function parseDate(date, options)
    {
        options = options || {};

        var a, day, month, year;
        a = date.split(/\D/);

        if (options.iso) {
            year = a.shift();
            month = a.shift();
            day = a.shift();
        } else {
            if (options.usa) {
                month = a.shift();
                day = a.shift();
            } else {
                day = a.shift();
                month = a.shift();
            }
            year = a.shift();
        }
        
        return new Date(month + '/' + day + '/' + year);
    }

    function formatTime(hour, minute, options)
    {
        var printMinute = minute;
        if (minute < 10) printMinute = '0' + minute;

        if (options.isoTime) {
            var printHour = hour
            if (printHour < 10) printHour = '0' + hour;
            return printHour + ':' + printMinute;
        } else {
            var printHour = hour % 12;
            if (printHour == 0) printHour = 12;

            if (options.meridiemUpperCase) {
            	 var half = (hour < 12) ? 'AM' : 'PM';
            } else {
            	 var half = (hour < 12) ? 'am' : 'pm';
            }

            return printHour + ':' + printMinute + half;
        }
    }

    function parseTime(text)
    {
        var match = match = /(\d+)\s*[:\-\.,]\s*(\d+)\s*(am|pm)?/i.exec(text);
        if (match && match.length >= 3) {
            var hour = Number(match[1]);
            var minute = Number(match[2])
            if (hour == 12 && match[3]) hour -= 12;
            if (match[3] && match[3].toLowerCase() == 'pm') hour += 12;
            return {
                hour:   hour,
                minute: minute
            };
        } else {
            return null;
        }
    }

    function timeToMinutes(time)
    {
        return time && (time.hour * 60 + time.minute);
    }

    /**
     * Generates calendar header, with month name, << and >> controls, and
     * initials for days of the week.
     */
    function renderCalendarHeader(element, year, month, options)
    {
        options = options || {};

        //Prepare thead element
        var thead = $('<thead />');
        var titleRow = $('<tr />').appendTo(thead);

        //Generate << (back a month) link
        $('<th />').addClass('monthCell').append(
          $('<a href="javascript:;">&laquo;</a>')
                  .addClass('prevMonth')
                  .mousedown(function(e) {
                      renderCalendarPage(element,
                          month == 0 ? (year - 1) : year,
                          month == 0 ? 11 : (month - 1), options
                      );
                      e.preventDefault();
                  })
        ).appendTo(titleRow);

        //Generate month title
        var month_label;
        if (options.iso) {
            month_label = year + '-' + (month < 9 ? '0': '') + (month + 1);
        } else {
            month_label = monthNames[month] + ' ' + year;
        }
        $('<th />').addClass('monthCell').attr('colSpan', 5).append(
            $('<a href="javascript:;">' + month_label +
                '</a>').addClass('monthName')
        ).appendTo(titleRow);

        //Generate >> (forward a month) link
        $('<th />').addClass('monthCell').append(
            $('<a href="javascript:;">&raquo;</a>')
                .addClass('nextMonth')
                .mousedown(function() {
                    renderCalendarPage(element,
                        month == 11 ? (year + 1) : year,
                        month == 11 ? 0 : (month + 1), options
                    );
                })
        ).appendTo(titleRow);

        //Generate weekday initials row
        var dayNames = $('<tr />').appendTo(thead);
        $.each(String('SMTWTFS').split(''), function(k, v) {
            $('<td />').addClass('dayName').append(v).appendTo(dayNames);
        });

        return thead;
    }

    function renderCalendarPage(element, year, month, options)
    {
        options = options || {};

        var today = getToday();

        var date = createDate(year, month, 1);

        //Wind end date forward to saturday week after month
        var endDate = monthAfter(year, month);
        var ff = 6 - endDate.getDay();
        if (ff < 6) ff += 7;
        for (var i = 0; i < ff; i++) endDate = dayAfter(endDate);

        var table = $('<table />');
        renderCalendarHeader(element, year, month, options).appendTo(table);

        var tbody = $('<tbody />').appendTo(table);
        var row = $('<tr />');

        //Rewind date to monday week before month
        var rewind = date.getDay() + 7;
        for (var i = 0; i < rewind; i++) date = dayBefore(date);

        while (date <= endDate) {
            var td = $('<td />')
                .addClass('day')
                .append(
                    $('<a href="javascript:;">' +
                        date.getDate() + '</a>'
                    ).click((function() {
                        var thisDate = date;

                        return function() {
                            if (options && options.selectDate) {
                                options.selectDate(thisDate);
                            }
                        }
                    }()))
                )
                .appendTo(row);

            var isToday     = areDatesEqual(date, today);
            var isSelected  = options.selected &&
                                areDatesEqual(options.selected, date);

            if (isToday)                    td.addClass('today');
            if (isSelected)                 td.addClass('selected');
            if (isToday && isSelected)      td.addClass('today_selected');
            if (date.getMonth() != month)   td.addClass('nonMonth');

            dow = date.getDay();
            if (dow == 6) {
                tbody.append(row);
                row = $('<tr />');
            }
            date = dayAfter(date);
        }
        if (row.children().length) {
            tbody.append(row);
        } else {
            row.remove();
        }

        element.empty().append(table);
    }

    function renderTimeSelect(element, options)
    {
        var minTime = timeToMinutes(options.minTime);
        var maxTime = timeToMinutes(options.maxTime);
        var defaultTime = timeToMinutes(options.defaultTime);
        var selection = options.selection && timeToMinutes(parseTime(options.selection));

        //Round selection to nearest time interval so that it matches a list item
        selection = selection && (
            (
                Math.floor((selection - minTime) / options.timeInterval) *
                options.timeInterval
            ) + minTime
        );

        var scrollTo;   //Element to scroll the dropdown box to when shown
        var ul = $('<ul />');

        for (var time = minTime; time <= maxTime; time += options.timeInterval)  {
            (function(time) {
            	var hour = Math.floor(time / 60);
            	var minute = time % 60;
                var timeText = formatTime(hour, minute, options);
                var fullText = timeText;
                if (options.showDuration) {
                    var duration = time - minTime;
                    if (duration < 60) {
                        fullText += ' (' + duration + ' mins)';
                    } else if (duration == 60) {
                        fullText += ' (1 hr)';
                    } else {
                        //Round partial hours to 1 decimal place
                        fullText += ' (' + (Math.round(duration / 60.0 * 10.0) / 10.0) + ' hrs)';
                    }
                }
                var li = $('<li />').append(
                    $('<a href="javascript:;">' + fullText + '</a>')
                    .click(function() {
                        if (options && options.selectTime) {
                            options.selectTime(timeText);
                        }
                    }).mousemove(function() {
                        $('li.selected', ul).removeClass('selected');
                    })
                ).appendTo(ul);

                //Set to scroll to the default hour, unless already set
                if (!scrollTo && time == defaultTime) scrollTo = li;

                if (selection == time) {
                    //Highlight selected item
                    li.addClass('selected');

                    //Set to scroll to the selected hour
                    //
                    //This is set even if scrollTo is already set, since
                    //scrolling to selected hour is more important than
                    //scrolling to default hour
                    scrollTo = li;
                }
            })(time);
        }
        if (scrollTo) {
            //Set timeout of zero so code runs immediately after any calling
            //functions are finished (this is needed, since box hasn't been
            //added to the DOM yet)
            setTimeout(function() {
                //Scroll the dropdown box so that scrollTo item is in
                //the middle
                element[0].scrollTop =
                    scrollTo[0].offsetTop - scrollTo.height() * 2;
            }, 0);
        }
        element.empty().append(ul);
    }

    function positionCalendrical(div, element, options) {
        if (options.positionInBody) {
            $('body').append(div);
            var offset = element.offset();
        } else {
            element.after(div);
            var offset = element.position();
        }
        div.css({
            position: 'absolute',
            left: offset.left,
            top: offset.top + element.height() +
                options.padding * 2
        });
    }
    
    $.fn.calendricalDate = function(options)
    {
        options = options || {};
        options.padding = options.padding || 4;

        return this.each(function() {
            var element = $(this);
            var div;
            var within = false;

            element.bind('focus click', function() {
                if (div) return;
                div = $('<div />')
                    .addClass('calendricalDatePopup')
                    .mouseenter(function() { within = true; })
                    .mouseleave(function() { within = false; })
                    .mousedown(function(e) {
                        e.preventDefault();
                    })
                positionCalendrical(div, element, options);

                var selected = parseDate(element.val(), options);
                if (!selected.getFullYear()) selected = getToday();

                renderCalendarPage(
                    div,
                    selected.getFullYear(),
                    selected.getMonth(), $.extend({}, options, {
                        selected: selected,
                        selectDate: function(date) {
                            within = false;
                            element.val(formatDate(date, options)).change();
                            div.remove();
                            div = null;
                            if (options.endDate) {
                                var endDate = parseDate(
                                    options.endDate.val(), options
                                );
                                if (endDate >= selected) {
                                    options.endDate.val(formatDate(
                                        new Date(
                                            date.getTime() +
                                            endDate.getTime() -
                                            selected.getTime()
                                        ),
                                        options
                                    ));
                                }
                            }
                        }
                    })
                );
            }).blur(function() {
                if (within){
                    if (div) element.focus();
                    return;
                }
                if (!div) return;
                div.remove();
                div = null;
            });
        });
    };

    $.fn.calendricalDateRange = function(options)
    {
        if (this.length >= 2) {
            $(this[0]).calendricalDate($.extend({
                endDate:   $(this[1])
            }, options));
            $(this[1]).calendricalDate(options);
        }
        return this;
    };

    $.fn.calendricalTime = function(options)
    {
        options = options || {};
        options.timeInterval = options.timeInterval || 30;
        options.padding = options.padding || 4;

        return this.each(function() {
            var element = $(this);
            var div;
            var within = false;

            element.attr('autocomplete', 'off');
            element.bind('focus click', function() {
                if (div) return;

                div = $('<div />')
                    .addClass('calendricalTimePopup')
                    .mouseenter(function() { within = true; })
                    .mouseleave(function() { within = false; })
                    .mousedown(function(e) {
                        e.preventDefault();
                    })
                positionCalendrical(div, element, options);

                var renderOptions = {
                    selection: element.val(),
                    selectTime: function(time) {
                        within = false;
                        element.val(time).change();
                        div.remove();
                        div = null;
                    },
                    isoTime:        options.isoTime || false,
                    meridiemUpperCase: options.meridiemUpperCase || false,
                    defaultTime:    options.defaultTime || {hour: 8, minute: 0},
                    minTime:        options.minTime || {hour: 0, minute: 0},
                    maxTime:        options.maxTime || {hour: 23, minute: 59},
                    timeInterval:   options.timeInterval || 30
                };

                if (options.startTime) {
                    var startTime = parseTime(options.startTime.val());
                    //Don't display duration if part of a datetime range,
                    //and start and end times are on different days
                    if (options.startDate &&
                        options.endDate &&
                        !areDatesEqual(parseDate(options.startDate.val(), options),
                        parseDate(options.endDate.val(), options))) {
                        startTime = null;
                    }
                    if (startTime) {
                        renderOptions.minTime = startTime;
                        renderOptions.defaultTime = startTime;
                        renderOptions.showDuration = true;
                        div.addClass('calendricalEndTimePopup');
                    }
                }

                renderTimeSelect(div, renderOptions);
            }).blur(function() {
                if (within){
                    if (div) element.focus();
                    return;
                }
                if (!div) return;
                div.remove();
                div = null;
            });
        });
    };

    $.fn.calendricalTimeRange = function(options)
    {
        if (this.length >= 2) {
            $(this[0]).calendricalTime(options);
            $(this[1]).calendricalTime($.extend({
                startTime: $(this[0])
            }, options));
        }
        return this;
    };

    $.fn.calendricalDateTimeRange = function(options)
    {
        if (this.length >= 4) {
            $(this[0]).calendricalDate($.extend({
                endDate:   $(this[2])
            }, options));
            $(this[1]).calendricalTime(options);
            $(this[2]).calendricalDate(options);
            $(this[3]).calendricalTime($.extend({
                startTime: $(this[1]),
                startDate: $(this[0]),
                endDate:   $(this[2])
            }, options));
        }
        return this;
    };
})(jQuery);