/*
num:ボタン選択をしたイベントの管理番号
0:左側
1:中央
2:右側
*/
function func(num)
{
	const ans=document.getElementById("answerNo");
	let txt="";
	if(ans.value ==num)
	{
		txt="正解です。";
	}
	else
	{
		txt="不正解です。";
	}
	//結果をメッセージで表示します。
	alert(txt);
	//正解の日付を表示<div>タグを表示状態にします
	document.getElementById("lbl1").style.display='block';
	document.getElementById("lbl2").style.display='block';
}
/*
乱数を返す処理
(例)
0-2なら3
0-9までなら10
*/
function random(num)
{
	return Math.floor(Math.random() * num);
}
/*
0から2までの3個の中から1個ををランダムに取得して正解の日付として使用します。
0:昨日
1:今日
2:明日
*/
let correct=random(3);

let txt="";
switch(correct)
{
	case 0:
		txt="昨日の日付を選択してください。";
		break;
	case 1:
		txt="今日の日付を選択してください。";
		break;
	default://case 2:
		txt="明日の日付を選択してください。";
		break;
}
document.getElementById("problem").innerHTML=txt;

let dateAdjust=0;
dateAdjust=correct - 1;
//正解の日付
date = new Date();
date.setDate(date.getDate() + dateAdjust);
//divタグに正解の日付を設定します
document.getElementById("lbl2").innerHTML=dateFormat(date);
//正解の日付の位置を０から2までの3個の中から1個ををランダムに取得して決めます。
//0:左側
//1:中央
//2:右側
let buttonPosition=random(3);

//正解のボタン番号を格納します
document.getElementById("answerNo").value=buttonPosition;

let num=0;
switch(buttonPosition)
{
	case 0:
		num=2;
		break;
	case 1:
		num=1;
		break;
	default://case 2:
		num=0;
		break;
}

//答えの日付から右側の日付となるように調整します
/*
ボタンイベントのjavascipt引数に下記の値を設定しておきます
そして正解判定はhiddenタグのanswerNoと比較判定します。
[引数に使用する値]
左側:0
中央:1
右側:2
*/
const left=document.getElementById("btnLeft");//左側
const center=document.getElementById("btnCenter");//中央
const right=document.getElementById("btnRight");//右側
//今日の日付
date = new Date();
date.setDate(date.getDate()+dateAdjust);
date.setDate(date.getDate()+num);
date.setDate(date.getDate());//右側
right.innerHTML=dateFormat(date);
date.setDate(date.getDate() - 1);
center.innerHTML=dateFormat(date);//中央
date.setDate(date.getDate() - 1);
left.innerHTML=dateFormat(date);//左側
//Dateクラスオブジェクトの値を使用して一定の日付書式にして返します
function dateFormat(date)
{
	let tmp ="";
	return date.getFullYear() + "/" 
	+ (date.getMonth() + 1) + "/" 
	+ date.getDate();
}

/*
num:Event number for which the button wa choose
0:left
1:center
2:right
*/
function funcEn(num)
{
	const ans=document.getElementById("answerNoEn");
	let txt="";
	if(ans.value ==num)
	{
		txt="correct";
	}
	else
	{
		txt="incorrect";
	}
	//The result will be displayed in a message.
	alert(txt);
	//show the correct answer date.<div>tag will be displayed.
	document.getElementById("lbl1En").style.display='block';
	document.getElementById("lbl2En").style.display='block';
}
/*
process to return a dondom number
ex.)
if it is between 0 and 2, it is 3.
if it is between 0 and 9, it is 10.

*/
function randomEn(num)
{
	return Math.floor(Math.random() * num);
}
/*
One of the three numbers between 0 and 2 will be randomly choose and used as the correct date.
0:yesterday
1:today
2:tomorrow
*/
let correctEn=randomEn(3);


let txtEn="";
switch(correctEn)
{
	case 0:
		txtEn="choose yesterday's date";
		break;
	case 1:
		txtEn="choose today's date";
		break;
	default://case 2:
		txtEn="choose tomorrow's date";
		break;
}
document.getElementById("problemEn").innerHTML=txtEn;
//adjust the value to use fro the date
//if it was yesterday, decrement the value from 0 to -1.

let dateAdjustEn=0;
dateAdjustEn=correctEn-1;
//set the correct date
date = new Date();
date.setDate(date.getDate() + dateAdjustEn);
//set the correct date in a div tag
document.getElementById("lbl2En").innerHTML=dateFormatEn(date);
//determine the position of the correct date by randomly choosing one of the three values from 0 to 2.
//0:left
//1:center
//2:right
let buttonPositionEn=randomEn(3);

//save the correct button number.
document.getElementById("answerNoEn").value=buttonPositionEn;

let numEn=0;
switch(buttonPositionEn)
{
	case 0:
		numEn=2;
		break;
	case 1:
		numEn=1;
		break;
	default://case 2:
		numEn=0;
		break;
}
//adjust the date so that it is to the right of the answer date.
/*
set the following value as the Javascript argument for the button event.
the correct answer will be determined by comparing it with the answerNo in the hidden tag.
[Value to use for argument]
left:0
center:1
right:2
*/
const leftEn=document.getElementById("btnLeftEn");//left
const centerEn=document.getElementById("btnCenterEn");//center
const rightEn=document.getElementById("btnRightEn");//right
//today date
date = new Date();
date.setDate(date.getDate()+dateAdjustEn);
date.setDate(date.getDate()+numEn);
date.setDate(date.getDate());//right
rightEn.innerHTML=dateFormatEn(date);
date.setDate(date.getDate() - 1);
centerEn.innerHTML=dateFormatEn(date);//center
date.setDate(date.getDate() - 1);
leftEn.innerHTML=dateFormatEn(date);//left
//Returns a date in a fixed format using the value of a Date class object
function dateFormatEn(date)
{
	let tmp ="";
/*
	return date.getFullYear() + "/" 
	+ (date.getMonth() + 1) + "/" 
	+ date.getDate();
*/
	return changeMonth(date.getMonth())+ " " 
	+ date.getDate() + "th " 
	+ ", " + date.getFullYear();
}
function changeMonth(month)
{
	let txt="";
	switch(month)
	{
		case 0:
			txt="Jan";
			break;
		case 1:
			txt="Feb";
			break;
		case 2:
			txt="Mar";
			break;
		case 3:
			txt="Apr";
			break;
		case 4:
			txt="May";
			break;
		case 5:
			txt="Jun";
			break;
		case 6:
			txt="Jul";
			break;
		case 7:
			txt="Aug";
			break;
		case 8:
			txt="Sep";
			break;
		case 9:
			txt="Oct";
			break;
		case 10:
			txt="Nov";
			break;
		case 11:
			txt="Dec";
			break;
	}
	return txt;
}