// 変数の設定
var monthDay = new Array(31,28,31,30,31,30,31,31,30,31,30,31);
var weekHead = new Array('日','月','火','水','木','金','土');

var today=new Date();
var thisYear = today.getYear();
if (thisYear < 1900) { thisYear = thisYear + 1900; }
var thisMonth = today.getMonth();
var thisDay = today.getDate();

function Cal(name, own, obj) {
  this.name = name;
  this.own = own;
  this.obj = obj;
  this.crntYear = 0;
  this.crntMonth = 0;
  this.crntDay = 0;
  this.crntMonthDay = 0;
  this.crntStartDay = 0;
  this.head = '';
  this.foot = '';
  return(this);
}

Cal.prototype.disp = function (yyyy, mm, dd) {
  this.setCrnt(yyyy, mm, dd);
  this.writeCal();
}

Cal.prototype.dispPrev = function () {
  this.setCrntPrev();
  this.writeCal();
}

Cal.prototype.dispNext = function () {
  this.setCrntNext();
  this.writeCal();
}

Cal.prototype.writeCal = function () {
  var d = this.obj.document;
  var str;
  var i, w;

  // HTMLヘッダの表示
  if (this.head) {
    d.open();
    d.writeln(this.head);
  }

  // カレンダタイトルの表示
  str = '';
  str += '<table border="2" class="cal_back"><tr>';
  str += '<th class="cal_head">';
  str += '<a href="javascript:';
  str += this.own + '.' + this.name + '.dispPrev();">△</a>';
  str += '</th>';
  str += '<th colspan="5" class="cal_head">';
  str += this.crntYear + '年' + (this.crntMonth + 1) + '月';
  str += '</th>';
  str += '<th class="cal_head">';
  str += '<a href="javascript:';
  str += this.own + '.' + this.name + '.dispNext();">▽</a>';
  str += '</th>';

  // 曜日タイトルの表示
  str += '</tr><tr>';
  str += '<th class="cal_sun">' + weekHead[0] + '</th>';
  for (i=1; i<6; i++) {
    str += '<th class="cal_back">' + weekHead[i] + '</th>';
  }
  str += '<th class="cal_sat">' + weekHead[6] + '</th>';

  // カレンダの表示
  str += '</tr><tr>';

  // 月初の空白表示
  for (i = 0; i < this.startDay; i++) {
    str += '<td class="cal_back">　</td>';
  }

  // 1ヶ月の表示
  for (i = 1, w = this.startDay; i <= this.crntMonthDay; i++, w++) {
    // 週単位の改行
    if (w > 6) {
      w = 0;
      str += '</tr></tr>';
    }
    // 今日の色分け表示
    if ((i == thisDay)
        && (this.crntMonth == thisMonth)
        && (this.crntYear == thisYear)) {
      str += '<td class="cal_today">' + i + '</td>';

    } else {
      // 曜日による色分け表示
      if (w == 0) {
        str += '<td class="cal_sun">' + i + '</td>';
      } else if (w == 6) {
        str += '<td class="cal_sat">' + i + '</td>';
      } else {
        str += '<td class="cal_back">' + i + '</td>';
      }
    }
  }

  // 月末の空白表示
  for (; w < 7; w++) {
    str += '<td class="cal_back">　</td>';
  }

  str += '</tr></table>';

  // カレンダの表示
  d.writeln(str);

  // HTMLフッタの表示
  if (this.foot) {
    d.writeln(this.foot);
    d.close();
  }
}

Cal.prototype.setHead = function (str) {
  this.head = str;
}

Cal.prototype.setFoot = function (str) {
  this.foot = str;
}

Cal.prototype.setCrnt = function (yyyy, mm, dd) {
//alert(this.crntYear+'/'+(this.crntMonth+1) + ', ' + yyyy+'/'+mm);

  // 年変換（1901-2099）
  if ((typeof(yyyy) == 'undefined') || (yyyy < 1901) || (yyyy > 2099)) {
    this.crntYear = thisYear;
  } else {
    this.crntYear = yyyy;
  }

  // 月変換（0-11）
  if ((typeof(mm) == 'undefined') || (mm < 1) || (mm > 12)) {
    this.crntMonth = thisMonth;
  } else {
    this.crntMonth = mm - 1;
  }
  // うるう年変換（1901年から2099年まで対応）
  if ((this.crntMonth == 1) && (this.crntYear % 4 == 0)) {
    this.crntMonthDay = 29;
  } else {
    this.crntMonthDay = monthDay[this.crntMonth];
  }

  // 日変換（1-31:this.crntMonthDay）
  if ((typeof(dd) == 'undefined') || (dd < 1) || (dd > this.crntMonthDay)) {
    this.crntDay = thisDay;
  } else {
    this.crntDay = dd;
  }

  // 開始曜日の設定
  var d1 = new Date(this.crntYear + '/' + (this.crntMonth + 1) + '/01');
  this.startDay = d1.getDay();
}

Cal.prototype.setCrntPrev = function () {
  // 前月のカレンダ表示
  var yyyy = this.crntYear;
  var mm = this.crntMonth;
  var dd = this.crntDay;

  if (mm < 1) {
    yyyy--;
    mm = 12;
  }

  this.setCrnt(yyyy, mm, dd);
}

Cal.prototype.setCrntNext = function () {
  // 翌月のカレンダ表示
  var yyyy = this.crntYear;
  var mm = this.crntMonth + 2;
  var dd = this.crntDay;

  if (mm > 12) {
    yyyy++;
    mm = 1;
  }

  this.setCrnt(yyyy, mm, dd);
}