var _$ = function (id) {
    return "string" == typeof id ? document.getelementbyid(id) : id;
};

var class = {
  create: function() {
    return function() {
      this.initialize.apply(this, arguments);
    }
  }
}

object.extend = function(destination, source) {
    for (var property in source) {
        destination[property] = source[property];
    }
    return destination;
}


var calendar = class.create();
calendar.prototype = {
  initialize: function(container, options) {
	this.container = _$(container);//容器(table结构)
	this.days = [];//日期对象列表
	
	this.setoptions(options);
	
	this.year = this.options.year;
	this.month = this.options.month;
	this.selectday = this.options.selectday ? new date(this.options.selectday) : null;
	this.onselectday = this.options.onselectday;
	this.ontoday = this.options.ontoday;
	this.onfinish = this.options.onfinish;	
	
	this.draw();
  },
  //设置默认属性
  setoptions: function(options) {
	this.options = {//默认值
		year:			new date().getfullyear(),//显示年
		month:			new date().getmonth() + 1,//显示月
		selectday:		null,//选择日期
		onselectday:	function(){},//在选择日期触发
		ontoday:		function(){},//在当天日期触发
		onfinish:		function(){}//日历画完后触发
	};
	object.extend(this.options, options || {});
  },
  //上一个月
  premonth: function() {
	//先取得上一个月的日期对象
	var d = new date(this.year, this.month - 2, 1);
	//再设置属性
	this.year = d.getfullyear();
	this.month = d.getmonth() + 1;
	//重新画日历
	this.draw();
  },  
  //下一个月
  nextmonth: function() {
	var d = new date(this.year, this.month, 1);
	this.year = d.getfullyear();
	this.month = d.getmonth() + 1;
	this.draw();
  },
  //画日历
  draw: function() {
	//用来保存日期列表
	var arr = [];
	//用当月第一天在一周中的日期值作为当月离第一天的天数
	for(var i = 1, firstday = new date(this.year, this.month - 1, 1).getday(); i <= firstday; i++){ arr.push("&nbsp;"); }
	//用当月最后一天在一个月中的日期值作为当月的天数
	for(var i = 1, monthday = new date(this.year, this.month, 0).getdate(); i <= monthday; i++){ arr.push(i); }
	
	var frag = document.createdocumentfragment();
	
	this.days = [];
	
	while(arr.length > 0){
		//每个星期插入一个tr
		var row = document.createelement("tr");
		//每个星期有7天
		for(var i = 1; i <= 7; i++){
			var cell = document.createelement("td");
			cell.innerhtml = "&nbsp;";
			
			if(arr.length > 0){
				var d = arr.shift();
				cell.innerhtml = d;
				if(d > 0){
					this.days[d] = cell;
					//判断是否今日
					if(this.issame(new date(this.year, this.month - 1, d), new date())){ this.ontoday(cell); }
					//判断是否选择日期
					if(this.selectday && this.issame(new date(this.year, this.month - 1, d), this.selectday)){ this.onselectday(cell); }
				}
			}
			row.appendchild(cell);
		}
		frag.appendchild(row);
	}
	
	//先清空内容再插入(ie的table不能用innerhtml)
	while(this.container.haschildnodes()){ this.container.removechild(this.container.firstchild); }
	this.container.appendchild(frag);
	
	this.onfinish();
  },
  //判断是否同一日
  issame: function(d1, d2) {
	return (d1.getfullyear() == d2.getfullyear() && d1.getmonth() == d2.getmonth() && d1.getdate() == d2.getdate());
  } 
};