function init() {
    var number = 0;		// Current quiz Number
    var csvquestion;		// Questions read from "quiz.csv"

    function prepare(n) {	// Prepare Question Page of Number n
	var qn = csvquestion[n];
	for (var id of ["title", "q", "choice0", "choice1", "choice2"]) {
	    document.getElementById(id).innerHTML = qn[id];
	}
	document.forms[0].reset();	// Reset radio buttons
	document.getElementById("image").setAttribute("src", "image/"+qn.image);
    }
    function judge() {
	var input = document.forms[0].q1.value;
	var selection = parseInt(input);
	var q = csvquestion[number];
	var ans = q.a
	var output = document.getElementById("output");
	output.innerHTML = "";
	if (input == "") {
	    alert('ボタンが選択されていません。');
	    return;
	} else if (selection == ans) {
	    output.innerHTML = "正解です: "
	} else {
	    output.innerHTML = "不正解です: ";
	}
	output.innerHTML += q["comment"+selection];
    }
    function prev() {
	number = Math.max(0, number-1);
	prepare(number);
    }
    function next() {
	number = Math.min(number+1, csvquestion.length-1);
	prepare(number);
    }
    fetch("./quiz.csv", {method: "GET"}).
	then(function(resp) {
	    return resp.text().then(function(text) {
		csvquestion = new CSV(text, {header: true}).parse();
		prepare(0);
	    });
	});
    document.getElementById("judge").addEventListener("click", judge);
    document.getElementById("prev").addEventListener("click", prev);
    document.getElementById("next").addEventListener("click", next);
    // prepare(0);
}
window.onload = init;