/*
  calendar.js - Calendar functions by Adrian Holovaty
  depends on core.js for utility functions like removeChildren or quickElement
  */
  
  // 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(' '),
      firstDayOfWeek: parseInt(get_format('FIRST_DAY_OF_WEEK')),
      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, selected) { // month = 1-12, year = 1-9999
          var today = new Date();
          var todayDay = today.getDate();
          var todayMonth = today.getMonth()+1;
          var todayYear = today.getFullYear();
          var todayClass = '';
  
          // Use UTC functions here because the date field does not contain time
          // and using the UTC function variants prevent the local time offset
          // from altering the date, specifically the day field.  For example:
          //
          // ```
          // var x = new Date('2013-10-02');
          // var day = x.getDate();
          // ```
          //
          // The day variable above will be 1 instead of 2 in, say, US Pacific time
          // zone.
          var isSelectedMonth = false;
          if (typeof selected != 'undefined') {
              isSelectedMonth = (selected.getUTCFullYear() == year && (selected.getUTCMonth()+1) == month);
          }
  
          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 + CalendarNamespace.firstDayOfWeek) % 7]);
          }
  
          var startingPos = new Date(year, month-1, 1 - CalendarNamespace.firstDayOfWeek).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.className = "nonday";
          }
  
          // Draw days of month
          var currentDay = 1;
          for (var i = startingPos; currentDay <= days; i++) {
              if (i%7 == 0 && currentDay != 1) {
                  tableRow = quickElement('tr', tableBody);
              }
              if ((currentDay==todayDay) && (month==todayMonth) && (year==todayYear)) {
                  todayClass='today';
              } else {
                  todayClass='';
              }
  
              // use UTC function; see above for explanation.
              if (isSelectedMonth && currentDay == selected.getUTCDate()) {
                  if (todayClass != '') todayClass += " ";
                  todayClass += "selected";
              }
  
              var cell = quickElement('td', tableRow, '', 'class', todayClass);
  
              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.className = "nonday";
          }
  
          calDiv.appendChild(calTable);
      }
  }
  
  // Calendar -- A calendar instance
  function Calendar(div_id, callback, selected) {
      // 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();
      if (typeof selected != 'undefined') {
          this.selected = selected;
      }
  }
  Calendar.prototype = {
      drawCurrent: function() {
          CalendarNamespace.draw(this.currentMonth, this.currentYear, this.div_id, this.callback, this.selected);
      },
      drawDate: function(month, year, selected) {
          this.currentMonth = month;
          this.currentYear = year;
  
          if(selected) {
              this.selected = selected;
          }
  
          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();
      }
  }