// Hide functions inside anonymous namespace.
(function() {

var PREV_MONTH_IMAGE = 'calendar_prev.png';
var NEXT_MONTH_IMAGE = 'calendar_next.png';
var PREV_YEAR_IMAGE = 'calendar_prev.png';
var NEXT_YEAR_IMAGE = 'calendar_next.png';

function get_element(id)
{
  return document.getElementById(id);
}

function is_child(el, ancestor) {
  while(el) {
    if (el == ancestor) 
      return true;
    el = el.parentNode;
  }
  return false;
}

// Because IE does not support DOM addEventListener.
function add_event(evt,fn) {
  document.all ? document.attachEvent('on'+evt, fn)
               : document.addEventListener(evt, fn, false);
}

// Global click event handler.
// If we've clicked outside the calendar then hide it.
function calendar_hide_check(evt) {
  if (calendar.element && !is_child(event_target(evt), calendar.element)) {
    calendar_hide();
  }
}

// Input control keypress handler.
function input_keypress(evt) {
  calendar_hide();
  return true;
}

// Gets the [x,y] position on the page of the element.
function get_xy(el) {
  var result = [0, 0];
  while (el) {
    result[0] += el.offsetLeft;
    result[1] += el.offsetTop;
    el = el.offsetParent;
  }
  return result;
}

// Return X coord of element.
function left(el) {
  return get_xy(el)[0];
}

// Return Y coord of element.
function top(el) {
  return get_xy(el)[1];
}
  
// Pad number or string to the left with pad character to a width of width characters.
function pad_left(value, pad_char, width) {
  var result = value + '';
  if (result.length >= width)
    return result.substr(0,width); // Return string truncated to width.
  for (var i = result.length; result.length < width; i++) {
    result = pad_char + result;
  }
  return result;
}

// Convert date to output display format.
// See date(1) man page for formatting specs.
function date_to_string(date, format) {
  if (!format) format = '%d %b %Y';  // Set default format.
  var result = format;
  result = result.replace('%e',date.getDate());
  result = result.replace('%d',pad_left(date.getDate(),'0',2));
  result = result.replace('%m',pad_left(date.getMonth()+1,'0',2));
  result = result.replace('%B',calendar.month_names[date.getMonth()]);
  result = result.replace('%b',calendar.month_names[date.getMonth()].substr(0,3));
  result = result.replace('%Y',date.getFullYear());
  result = result.replace('%y',(date.getFullYear()+'').substr(2));
  return result;
}

/*
  Convert input date string to date (or undefined if not a date string).
  The following date formats are supported:

  - ISO date format: yyyy-mm-dd, for example '2001-12-25'
  - d[ mmm[ yy[yy]]]: examples: '22', '22 feb', '22 feb 2003', '22 feb 03', '22 February 2003'
  - d[/m/[yy[yy]]]: examples: '21', '21/7', '21/7/07', '21/7/2007'

*/
function string_to_date(s) {
  var result = undefined;
  var today = new Date;
  if (mo = s.match(/^\s*(\d{4})-(\d{1,2})-(\d{1,2})\s*$/)) {
    // ISO date format 'yyyy-mm-dd'.
    result = new Date(mo[1], Number(mo[2])-1, mo[3]);
  }
  else if (mo = s.match(/^\s*(\d{1,2})(?:(?:\s+|-)([a-zA-Z]{3,9})(?:(?:\s+|-)(\d{2}(?:\d{2})?))?)?\s*$/)) {
    // 'd mmmm yyyy' format and abbreviations.
    mo[2] = mo[2] ? calendar.month_numbers[mo[2].substr(0,3).toLowerCase()] : today.getMonth();
    mo[3] = mo[3] || today.getFullYear();
    result = new Date(mo[3], mo[2], mo[1]);
  }
  else if (mo = s.match(/^\s*(\d{1,2})(?:(?:\/)(\d{1,2})(?:(?:\/)(\d{2}(?:\d{2})?))?)?\s*$/)) {
    // 'd/m/yyyy' format and abbreviations.
    mo[2] = mo[2] ? Number(mo[2])-1 : today.getMonth();
    mo[3] = mo[3] || today.getFullYear();
    mo[3] = Number(mo[3]);
    if (mo[3] < 99) mo[3] += 2000;
    result = new Date(mo[3], mo[2], mo[1]);
  }
  return result;
}

// Set day number cell styles: 'normal', 'hover', 'selected', 'today'.
function set_day_styles(day, styles) {
  day.className = 'day_number ' + styles;
  if (styles != 'hover') day._day_styles = styles;
}

// Because IE does not pass event to event handler, get it from global event.
function event_object(evt) {
  return evt ? evt : window.event;
}

// Return the element that triggered the event.
// Handle event model idiosyncrasies
// (see also http://www.quirksmode.org/js/events_properties.html)
function event_target(evt) {
  var result;
  evt = event_object(evt);
  if (evt.target)
    result = evt.target;
  else if (evt.srcElement)      // IE
    result = evt.srcElement;
  if (result.nodeType == 3)
    result = result.parentNode; // Safari
  return result;
}

// Calendar mouseover handler.
function calendar_over(evt) {
  set_day_styles(event_target(evt), 'hover');
}

function calendar_out(evt) {
  var el = event_target(evt);
  set_day_styles(el, el._day_styles);
}

function calendar_click(evt) {
  var date = calendar.dates[event_target(evt).id.substr('calendar_day_'.length)];
  calendar.input_element.value = date_to_string(date, calendar.format);
  calendar_hide();
}

function is_leap_year(year) { 
  return (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) ? true : false;
}

function last_day_of_month(year,month) {
  var month_days = new Array(31,28,31,30,31,30,31,31,30,31,30,31);
  var result = month_days[month]
  if (is_leap_year(year) && month == 1)
    result++;
  return result
}

// Return td element for cell number n (1..42).
function day_cell(n) {
  return get_element('calendar_day_'+n);
}

// Return true if dates d1 and d2 are the same.
function dates_equal(d1, d2) {
  if (!d1 || !d2)
    return false;
  else
    return d1.getDate() == d2.getDate() &&
           d1.getMonth() == d2.getMonth() &&
           d1.getFullYear() == d2.getFullYear();
}

// Advance calendar by n months (n: -11..11).
function calendar_increment(n) {
  var m = calendar.month_date.getMonth();
  var y = calendar.month_date.getFullYear();
  m += n;
  if (n<0 ? (m < 0) : (m > 11)) {
    m += n<0 ? 12 : -12;
    y += n<0 ? -1 : 1;
  }
  calendar.month_date.setFullYear(y, m, 1);
  calendar_update();
}

function calendar_next_month() {
  calendar_increment(1);
}

function calendar_prev_month() {
  calendar_increment(-1);
}

function calendar_next_year() {
  calendar_increment(12);
}

function calendar_prev_year() {
  calendar_increment(-12);
}


function calendar_show() {
  calendar.element.style.display = '';
}

function calendar_hide() {
  calendar.element.style.display = 'none';
}

// Refresh the calendar table dates to month of calendar.month_date and
// highlight, if necessary, calendar.input_date and today's date. Link mouse
// handlers to each cell and update calendar.dates[].
//
function calendar_update() {
  var m = calendar.month_date.getMonth();
  var y = calendar.month_date.getFullYear();
  var day1 = calendar.month_date.getDay(); // Day of week: 0..6 of first day of the month.
  get_element('calendar_header').innerHTML = calendar.month_names[m].substr(0,3).toUpperCase()+ ' ' + y;
  get_element('calendar_prev_month').onclick = calendar_prev_month;
  get_element('calendar_next_month').onclick = calendar_next_month;
  get_element('calendar_prev_year').onclick = calendar_prev_year;
  get_element('calendar_next_year').onclick = calendar_next_year;

// Iterate through the 42 calendar date boxes.
  var hide_last_row = false;
  for(var i=1; i<=42; i++) {
    var el = day_cell(i);   // Calendar day cell.
    var styles = 'normal';
    if (i >= day1+1 && i <= day1+last_day_of_month(y,m)) {
      var d = i-day1;  // Day of month.
      var date = new Date(y,m,d);
      if (dates_equal(date, calendar.input_date))
        styles = 'selected';
      if (dates_equal(date, new Date()))
        styles += ' today';
      if ( i % 7 == 0 || i % 7 == 1)
        styles += ' weekend';
      el.onmouseover = calendar_over;
      el.onmouseout = calendar_out;
      el.onclick = calendar_click;
      el.innerHTML = d;
      // Date value for setting input element.
      calendar.dates[i] = date;
    }
    else {
      styles = 'blank';
      el.innerHTML = '&nbsp;';
      el.onmouseover = null;
      el.onmouseout = null;
      el.onclick = null;
      el.style.cursor = 'default';
      // If the first cell of the last row has no date then hide the whole row.
      if (i == 36)
        hide_last_row = true;
    }
    set_day_styles(el, styles);
  }
  var rows = calendar.element.getElementsByTagName('tr');
  rows[7].style.display = hide_last_row ? 'none' : '';
}

/*
  This single public function does all the work.
  Optional options object has format and images_dir properties.
  Call it from text input element onfocus and onclick events.
  See calendar_example.html for example usage.
*/
function calendar_open(input_element, options) {
  calendar.input_element = input_element;
  options = options || {};
  calendar.format = options.format;
  if (options.month_names) {
    calendar.month_names = options.month_names;
  }
  if (options.day_names) {
    calendar.day_names = options.day_names;
  }
  // Built month numbers lookup.
  for (var i=0; i < calendar.month_names.length; i++) {
    calendar.month_numbers[calendar.month_names[i].substr(0,3).toLowerCase()] = i;
  }
  // Set day name cells.
  var day_names = calendar.element.getElementsByTagName('tr')[1].childNodes;
  for (var i=0; i < day_names.length; i++) {
    day_names[i].innerHTML = calendar.day_names[i].substr(0,3);
    if ( i == 0 || i == 6)
      day_names[i].className += ' weekend';
  }
  var images_dir = options.images_dir || '.';
  // Set up previous and next images.
  var images = calendar.element.getElementsByTagName('img');
  if (images.length == 0) {
    get_element('calendar_prev_year').appendChild(document.createElement('img'));
    get_element('calendar_prev_month').appendChild(document.createElement('img'));
    get_element('calendar_next_month').appendChild(document.createElement('img'));
    get_element('calendar_next_year').appendChild(document.createElement('img'));
    images = calendar.element.getElementsByTagName('img');
  }
  images[0].src = images_dir + '/' + PREV_YEAR_IMAGE;
  images[1].src = images_dir + '/' + PREV_MONTH_IMAGE;
  images[2].src = images_dir + '/' + NEXT_MONTH_IMAGE;
  images[3].src = images_dir + '/' + NEXT_YEAR_IMAGE;
  add_event('click', calendar_hide_check);
  input_element.onkeypress = input_keypress;
  // Position calendar by input element.
  calendar.element.style.left = left(input_element) + 'px';
  calendar.element.style.top = (top(input_element) + input_element.offsetHeight) + 'px';
  calendar_show();
  // Parse input date.
  var date = string_to_date(input_element.value);
  if (date) {
    calendar.input_date = date;
    calendar.month_date = new Date(date);
  }
  else {
    calendar.input_date = undefined;
    calendar.month_date = new Date;
  }
  calendar.month_date.setDate(1);
  calendar_update();
}


/*
  Build calendar table.
*/
document.write('<table id="calendar_control" style="display:none">');
// Header row.
document.write('<tr>');
document.write('<td id="calendar_prev_year" title="previous year"></td>');
document.write('<td id="calendar_prev_month" title="previous month"></td>');
document.write('<td id="calendar_header" colspan="3"></td>');
document.write('<td id="calendar_next_month" title="next month"></td>');
document.write('<td id="calendar_next_year" title="next year"></td>');

document.write('</tr>');
// Day letters row.
document.write('<tr>');
for (var i=0; i < 7; i++) {
  document.write('<td class="day_letter"></td>');
}
document.write('</tr>');
// Day numbers rows.
for(var n=1, i=0; i<6 ;i++) {
  document.write('<tr>');
  for(var j=0; j<7; j++,n++) {
    document.write('<td id="calendar_day_' + n + '" class="day_number normal"></td>');
  }
  document.write('</tr>');
}
document.write('</table>');

/*
  Namespace globals.
*/
calendar = {                        // Calendar properties.
  dates: new Array(6*7),            // Date values for each calendar day.
  element: get_element('calendar_control'),
  input_element: undefined,         // Calendar input element, set by calendar_show().
  input_date: undefined,            // Date value of input element, set by calendar_show().
  month_date: undefined,            // First day of calendar month.
  format: undefined,                // The date display format, set by calendar_show().
  month_names: new Array('January','February','March','April','May','June',
                         'July','August','September','October','November','December'),
  day_names: new Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'),
  month_numbers: {}                 // Reverse lookup for month numbers.
}
window['calendar_open'] = calendar_open;  // The only publicly accessible function.

// Close anonymous namespace.
})();