function show_row (id) {
  var row = document.getElementById (id);
  if (row.nodeName && row.nodeName.toUpperCase () == 'TR') {
    row.style.display = 'table-row';
  } else {
    alert ("Tried show_row on " + id + " nodeName: " + row.nodeName);
  }
}

function hide_row (id) {
  var row = document.getElementById (id);
  if (row.nodeName && row.nodeName.toUpperCase () == 'TR') {
    row.style.display = 'none';
  } else {
    alert ("Tried hide_row on " + id + " nodeName: " + row.nodeName);
  }
}

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, on_change_function_name) {
  
  if (on_change_function_name) {
    var sep = '?';
    if (url.search (/\?/)) {
      sep = '&';
    }
    
    url += sep + 'onchange=' + encodeURIComponent (on_change_function_name);
  }
  
  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 ();
  var on_change_function_name = '';
  
  this.init = function (form_name, prefix, change_func_name) {
    this.opener_form = eval ('window.opener.document.forms.' + form_name);
    this.prefix = prefix;
    if (change_func_name) this.on_change_function_name = change_func_name;
    
    // Pull values from calling page
    var init_month = find_form_input (this.opener_form, prefix + '[m]');
    this.month = Number (init_month.value);
    //alert ('this.month: ' + this.month);
    
    var old_year_field = find_form_input (this.opener_form, prefix + '[y]');
    this.year = old_year_field.value;
    
    // if selected date is valid, use it, otherwise use 0001-01-01
    this.selected_date = new Date ();
    var init_day = find_form_input (this.opener_form, prefix + '[d]');
    var selected_day = Number (init_day.value);
    if (!isNaN (this.month) && !isNaN (selected_day) && this.year > 0) {
      this.selected_date.setFullYear (this.year);
      this.selected_date.setMonth (this.month - 1);
      this.selected_date.setDate (selected_day);
    } else {
      this.selected_date.setFullYear (1);
      this.selected_date.setMonth (0);
      this.selected_date.setDate (1);
    }
    
    
    // If drop-downs were left blank on calling page, set a default (today)
    // if (this.month <= 0 || this.month > 12) this.month = 1;
    this.curr_date = new Date ();
    if (this.month <= 0 || this.month > 12 || isNaN(this.month)) this.month = this.curr_date.getMonth () + 1;
    if (this.year <= 0) this.year = this.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;
    
    // alert ("Month: " + month_field.value);
    
    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 () {
        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;
    
    var current_year_month_match = false;
    var selected_year_month_match = false;
    if (this.month == this.curr_date.getMonth () + 1 && this.year == this.curr_date.getFullYear()) {
      current_year_month_match = true;
    }
    if (this.month == this.selected_date.getMonth () + 1 && this.year == this.selected_date.getFullYear()) {
      selected_year_month_match = true;
    }
    
    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 (
        current_year_month_match && (i + 1 == this.curr_date.getDate ()),
        selected_year_month_match && (i + 1 == this.selected_date.getDate ()))
      );
      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));
    
    // fire onchange event if date has changed
    if (Number (day_field.value) != Number (day) ||
        Number (month_field.value) != Number (month) ||
        Number (year_field.value) != Number (this.year)) {
      var has_changed = 1;
    }
    
    day_field.value = day;
    month_field.value = month;
    year_field.value = this.year;
    
    if (has_changed && this.on_change_function_name) {
      var code = 'window.opener.' + this.on_change_function_name
        + ' ("' + this.opener_form.name.replace('"', '\"') + '", "' + this.prefix.replace('"', '\"') + '")';
      
      eval (code);
    }
    
    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);
    if (cell.className == '' || cell.className == 'current') {
      cell.className = 'current';
    } else {
      cell.className += ' current';
    }
  }
  this.td.onmouseout = function () {
    cell = document.getElementById ('day_' + input);
    if (cell.className == 'current') {
      cell.className = '';
    } else {
      cell.className = cell.className.replace (' current', '');
    }
  }
  this.td.onclick = function () {
    my_cal.submit (input);
  }
  
  this.getTd = function (is_today, is_selected) {
    
    var td = this.td;
    
    /*
    if (is_today == true) {
      var bolder = document.createElement ('strong');
      td = this.td.cloneNode (true);
      
      bolder.appendChild (td.firstChild);
      td.appendChild (bolder);
    } else {
      td = this.td;
    }
    */
    
    if (is_selected) {
      td.className = 'selected';
    } else {
      td.className = '';
    }
    
    if (is_today) {
      td.style.fontWeight = 'bold';
    } else {
      td.style.fontWeight = 'normal';
    }
    
    return 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
  }
}

/**
* Checks if the specified datetime is valid
* @param string date_time An ISO 8601 formatted (YYYY-MM-DD HH:MM:SS) datetime to check
* @return bool True if the datetime is valid, false otherwise
**/
function is_valid_date_time (date_time) {
  
  var date_time_parts = date_time.split (' ');
  if (date_time_parts.length == 2) {
    return is_valid_date (date_time_parts[0]) && is_valid_time (date_time_parts[1]);
  } else {
    return false;
  }
  
}

/**
* Checks if the specified date is valid
* @param string date An ISO 8601 formatted (YYYY-MM-DD) date to check
* @return bool True if the date is valid, false otherwise
**/
function is_valid_date (date) {
  
  var date_parts = date.split ('-');
  var result = true;
  
  if (date_parts.length == 3) {
    
    var year = date_parts[0];
    var month = date_parts[1];
    var day = date_parts[2];
    
    if (year.length != 4 || year == 0) {
      result = false;
    } else {
      if (month.length != 2 || day.length != 2 || day <= 0 || month <= 0 || month > 12) {
        result = false;
      } else {
        
        var month_days = {
          1: 31,
          2: 28,
          3: 31,
          4: 30,
          5: 31,
          6: 30,
          7: 31,
          8: 31,
          9: 30,
          10: 31,
          11: 30,
          12: 31
        };
        if (is_leap_year (year)) {
          month_days[2] = 29;
        }
        
        if (day > month_days[Number (month)]) {
          result = false;
        }
      }
    }
    
  } else {
    result = false;
  }
  
  return result;
}

/**
* Checks if the specified time is valid
* 
* @param string time The ISO 8601 formatted (HH:MM:SS) time to check
* @return bool True if the time is valid, false otherwise
**/
function is_valid_time (time) {
  
  var time_parts = time.split (':');
  var result = true;
  
  if (time_parts.length == 3) {
    
    var hour = time_parts[0];
    var min = time_parts[1];
    var sec = time_parts[2];
    
    if (hour.length != 2 || hour < 0 || hour > 23) {
      result = false;
    } else if (min.length != 2 || min < 0 || min > 59) {
      result = false;
    } else if (sec.length != 2 || sec < 0 || sec > 59) {
      result = false;
    }
    
  } else {
    result = false;
  }
  
  return result;
}

function get_radio_value (radio_el) {
  
  if (typeof (radio_el) == 'object' && radio_el.length > 0) {
    
    for (var i in radio_el) {
      if (radio_el[i].checked == true) {
        return radio_el[i].value;
      }
    }
  }
  return false;
}

/*
function calendar_over (element) {
  element.style.backgroundColor = 'FF0000';
}

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

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