function find_form (element) {
  var parent = element;
  var response;
  while (parent.nodeName.toUpperCase () != 'FORM') {
    parent = parent.parentNode;
    if (parent == null) {
      break;
    }
    response += parent.nodeName + "\n";
  }
  // window.alert (response + ': ' + parent.name);
  return parent;
}

function cal_popup (url) {
  var win = window.open (url, '_blank',
    'width=265,height=190,directories=0,location=0,menubar=0,resizable=1,scrollbars=0,status=0,toolbar=0');
  win.focus ();
}

function find_form_input (form, name) {
  var inputs = form.elements;
  var found = null;
  for (i = 0; i < inputs.length; i++) {
    if (inputs[i].name == name) {
      found = inputs[i];
      break;
    }
  }
  return found;
}

function PopupCalendar () {
  
  var prefix;
  var opener_form;
  var month;
  var year;
  var min_year;                                                                                               
  var max_year;
  var cal_dates;
  var date = new Date ();
  
  this.init = function (form_name, prefix) {
    this.opener_form = eval ('window.opener.document.forms.' + form_name);
    this.prefix = prefix;
    
    // Pull values from calling page
    var init_month = find_form_input (this.opener_form, prefix + '[m]');
    this.month = init_month.value;
    
    var old_year_field = find_form_input (this.opener_form, prefix + '[y]');
    this.year = old_year_field.value;
    
    // If drop-downs were left blank on calling page, set a default (today)
    // if (this.month <= 0 || this.month > 12) this.month = 1;
    var curr_date = new Date ();
    if (this.month <= 0 || this.month > 12) this.month = curr_date.getMonth () + 1;
    if (this.year <= 0) this.year = curr_date.getFullYear();
    
    // alert ('this.month: ' + this.month);
    
    var min = 10000;
    var max = -1;
    var year_field = document.getElementById ('year');
    var month_field = document.getElementById ('month');
    month_field.value = this.month;
    if (year_field == null) alert ("No year field");
    var year_set = false;
    var first_year = -1;
    
    var current_index = 0;
    if (old_year_field.options) {
      for (i = 0; i < old_year_field.options.length; i++) {
        if (old_year_field.options[i].value > 0) {
          // if (this.year == 0) this.year = old_year_field.options[i].value;
          if (first_year == -1) first_year = i;
          year_field.options[current_index] = new Option (old_year_field.options[i].value,
            old_year_field.options[i].value);
          if (year_field.options[current_index].value == this.year) {
            year_field.selectedIndex = current_index;
            year_set = true;
          }
          current_index++;
        }
      }
    }
    if (old_year_field.options) {
      if (!year_set) {
        this.year = old_year_field.options[first_year].value;
        year_field.value = this.year;
      }
    } else {
      // if there's not a year select on the caller page, use a text field on the popup as well
      // year_field.type = 'text';
      new_year_field = document.createElement ('input');
      new_year_field.attributes.type = 'text';
      new_year_field.attributes.size = 4;
      new_year_field.size = 4;
      new_year_field.value = this.year;
      new_year_field.onchange =  function () { eval ("my_cal.set_year (this.value); my_cal.draw ();") };
      year_field.parentNode.replaceChild (new_year_field, year_field);
    }
    
    this.cal_dates = new Array ();
    for (i = 1; i <= 31; i++) {
      this.cal_dates[i] = new PopupCalendarDate (i);
    }
    
  }
  
  this.draw = function () {
    var table = document.getElementById ('cal');
    
    click_dates = new Array ();
    
    // TODO: remove old elements
    var children = table.childNodes;
    for (i = children.length - 1; i >= 0; i--) {
      table.removeChild (children.item (i));
    }
    
    // work out the first day of the month
    date.setDate (1);
    date.setMonth (this.month - 1);
    date.setFullYear (this.year);
    var start_day = date.getDay ();
    
    var tr;
    var td;
    var td_count = 0;
    
    tr = document.createElement ('tr');
    table.appendChild (tr);
    
    for (i = 0; i < start_day; i++) {
      td = document.createElement ('td');
      td.appendChild (document.createTextNode ('\u00a0')); // &nbsp;
      tr.appendChild (td);
      td_count++;
    }
    
    var month_days = days_per_month (this.month, this.year);
    // alert (month_days + " days in " + this.month + "/" + this.year);
    var action_script;
    
    for (i = 0; i < month_days; i++) {
      if (td_count == 7) {
        table.appendChild (document.createTextNode ("\n"));
        tr = document.createElement ('tr');
        table.appendChild (tr);
        td_count = 0;
      }
      tr.appendChild (this.cal_dates[i + 1].getTd ());
      td_count++;
    }
    while (td_count < 7) {
      td = document.createElement ('td');
      td.appendChild (document.createTextNode ('\u00a0'));
      tr.appendChild (td);
      td_count++;
    }
    
  }
  
  this.set_month = function (month) {
    this.month = month;
  }
  
  this.set_year = function (year) {
    this.year = year;
  }
  
  this.submit = function (day) {
    var month = String (this.month);
    day = String (day);
    if (month.length < 2) month = '0'.concat (month);
    if (day.length < 2) day = '0'.concat (day);
    
    var day_field = find_form_input (this.opener_form, this.prefix + '[d]');
    var month_field = find_form_input (this.opener_form, this.prefix + '[m]');
    var year_field = find_form_input (this.opener_form, this.prefix + '[y]');
    
    // alert ('Setting date '+ this.year.concat ('.'). concat (month). concat ('.'). concat (day));
    
    day_field.value = day;
    month_field.value = month;
    year_field.value = this.year;
    window.close ();
  }
  
}

function PopupCalendarDate (input) {
  this.td = document.createElement ('td');
  this.td.appendChild (document.createTextNode (input));
  this.td.style.cursor = 'pointer';
  this.td.style.textAlign = 'center';
  this.td.setAttribute ('id', 'day_' + input);
  this.td.onmouseover = function () {
    cell = document.getElementById ('day_' + input);
    // if (cell == null) alert ('No cell with id day_' + input);
    cell.style.backgroundColor = 'e9bac4';
  }
  this.td.onmouseout = function () {
    cell = document.getElementById ('day_' + input);
    cell.style.backgroundColor = 'FFFFFF';
  }
  this.td.onmouseup = function () {
    my_cal.submit (input);
  }
  
  this.getTd = function () {
    return this.td;
  }
}

function days_per_month (month, year) {
  var res;
  switch (Number (month)) {
    case 1:  res = 31; break;
    case 2:
      if (is_leap_year (year)) {
        res = 29; // leap year
      } else {
        res = 28; // common year
      }
      break;
    case 3:  res = 31; break;
    case 4:  res = 30; break;
    case 5:  res = 31; break;
    case 6:  res = 30; break;
    case 7:  res = 31; break;
    case 8:  res = 31; break;
    case 9:  res = 30; break;
    case 10: res = 31; break;
    case 11: res = 30; break;
    case 12: res = 31; break;
    default:
      alert ('Error: ' + month + ' is not between 1 and 12');
  }
  // alert (res + ' days in ' + month + '/' + year);
  return res;
}

function is_leap_year (year) {
  if (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) {
    return true; // leap year (divisible by 4, excluding those that are divisible by 100 but not 400)
  } else {
    return false; // common year
  }
}

/*
function calendar_over (element) {
  element.style.backgroundColor = 'e9bac4';
}

function calendar_out (element) {
  element.style.backgroundColor = 'FFFFFF';
}

calendar_pass_back = function (data) {
  alert ('Pass back ' + data);
}
*/