/*

calendar.js - Calendar functions by Adrian Holovaty

*/

function removeChildren(a) { // "a" is reference to an object

    while (a.hasChildNodes()) a.removeChild(a.lastChild);

}

// quickElement(tagType, parentReference, textInChildNode, [, attribute, attributeValue ...]);

function quickElement() {

    var obj = document.createElement(arguments[0]);

    if (arguments[2] != '' && arguments[2] != null) {

        var textNode = document.createTextNode(arguments[2]);

        obj.appendChild(textNode);

    }

    var len = arguments.length;

    for (var i = 3; i < len; i += 2) {

        obj.setAttribute(arguments[i], arguments[i+1]);

    }

    arguments[1].appendChild(obj);

    return obj;

}

// CalendarNamespace -- Provides a collection of HTML calendar-related helper functions

var CalendarNamespace = {

    monthsOfYear: gettext('January February March April May June July August September October November December').split(' '),

    daysOfWeek: gettext('S M T W T F S').split(' '),

    isLeapYear: function(year) {

        return (((year % 4)==0) && ((year % 100)!=0) || ((year % 400)==0));

    },

    getDaysInMonth: function(month,year) {

        var days;

        if (month==1 || month==3 || month==5 || month==7 || month==8 || month==10 || month==12) {

            days = 31;

        }

        else if (month==4 || month==6 || month==9 || month==11) {

            days = 30;

        }

        else if (month==2 && CalendarNamespace.isLeapYear(year)) {

            days = 29;

        }

        else {

            days = 28;

        }

        return days;

    },

    draw: function(month, year, div_id, callback) { // month = 1-12, year = 1-9999

        month = parseInt(month);

        year = parseInt(year);

        var calDiv = document.getElementById(div_id);

        removeChildren(calDiv);

        var calTable = document.createElement('table');

        quickElement('caption', calTable, CalendarNamespace.monthsOfYear[month-1] + ' ' + year);

        var tableBody = quickElement('tbody', calTable);

        // Draw days-of-week header

        var tableRow = quickElement('tr', tableBody);

        for (var i = 0; i < 7; i++) {

            quickElement('th', tableRow, CalendarNamespace.daysOfWeek[i]);

        }

        var startingPos = new Date(year, month-1, 1).getDay();

        var days = CalendarNamespace.getDaysInMonth(month, year);

        // Draw blanks before first of month

        tableRow = quickElement('tr', tableBody);

        for (var i = 0; i < startingPos; i++) {

            var _cell = quickElement('td', tableRow, ' ');

            _cell.style.backgroundColor = '#f3f3f3';

        }

        // Draw days of month

        var currentDay = 1;

        for (var i = startingPos; currentDay <= days; i++) {

            if (i%7 == 0 && currentDay != 1) {

                tableRow = quickElement('tr', tableBody);

            }

            var cell = quickElement('td', tableRow, '');

            quickElement('a', cell, currentDay, 'href', 'javascript:void(' + callback + '('+year+','+month+','+currentDay+'));');

            currentDay++;

        }

        // Draw blanks after end of month (optional, but makes for valid code)

        while (tableRow.childNodes.length < 7) {

            var _cell = quickElement('td', tableRow, ' ');

            _cell.style.backgroundColor = '#f3f3f3';

        }

        calDiv.appendChild(calTable);

    }

}

// Calendar -- A calendar instance

function Calendar(div_id, callback) {

    // div_id (string) is the ID of the element in which the calendar will

    //     be displayed

    // callback (string) is the name of a JavaScript function that will be

    //     called with the parameters (year, month, day) when a day in the

    //     calendar is clicked

    this.div_id = div_id;

    this.callback = callback;

    this.today = new Date();

    this.currentMonth = this.today.getMonth() + 1;

    this.currentYear = this.today.getFullYear();

}

Calendar.prototype = {

    drawCurrent: function() {

        CalendarNamespace.draw(this.currentMonth, this.currentYear, this.div_id, this.callback);

    },

    drawDate: function(month, year) {

        this.currentMonth = month;

        this.currentYear = year;

        this.drawCurrent();

    },

    drawPreviousMonth: function() {

        if (this.currentMonth == 1) {

            this.currentMonth = 12;

            this.currentYear--;

        }

        else {

            this.currentMonth--;

        }

        this.drawCurrent();

    },

    drawNextMonth: function() {

        if (this.currentMonth == 12) {

            this.currentMonth = 1;

            this.currentYear++;

        }

        else {

            this.currentMonth++;

        }

        this.drawCurrent();

    },

    drawPreviousYear: function() {

        this.currentYear--;

        this.drawCurrent();

    },

    drawNextYear: function() {

        this.currentYear++;

        this.drawCurrent();

    }

}