const DIFFICULTIES = [
    { id: 'easy', label: '쉬움' },
    { id: 'medium', label: '보통' },
    { id: 'hard', label: '어려움' },
];

const fillSelect = (select, values) => {
    select.replaceChildren(
        ...values.map((value) => {
            const option = document.createElement('option');
            option.value = value;
            option.textContent = value;
            return option;
        })
    );
    select.disabled = values.length === 0;
};

class OptionPage extends HTMLElement {
    async connectedCallback() {
        this.className = 'screen';
        this.innerHTML = `
            <div class="hero">
                <picture>
                    <source srcset="/public/images/logo-dark.png"
                            media="(prefers-color-scheme: dark)">
                    <img src="/public/images/logo-light.png" alt="CogMind">
                </picture>
                <h1>공부의 시작은 나를 아는것</h1>
                <p>문제를 풀면 AI가 여러분을 메타인지하고 피드백 해줘요.</p>
            </div>
            <div class="card">
                <div class="field">
                    <label for="student">이름</label>
                    <input id="student" type="text" placeholder="예: 이승준" autocomplete="off"
                           maxlength="30">
                </div>
                <div class="field">
                    <label for="school">학교 종류</label>
                    <select id="school"></select>
                </div>
                <div class="row" style="margin-top:16px">
                    <div class="field" style="margin:0">
                        <label for="subject">과목</label>
                        <select id="subject"></select>
                    </div>
                    <div class="field" style="margin:0">
                        <label for="chapter">단원</label>
                        <select id="chapter"></select>
                    </div>
                </div>
                <div class="row" style="margin-top:16px">
                    <div class="field" style="margin:0">
                        <label>난이도</label>
                        <div id="difficulty"></div>
                    </div>
                    <div class="field" style="margin:0">
                        <label for="amount">문항 수 (1–20)</label>
                        <input id="amount" type="number" min="1" max="20" value="5">
                    </div>
                </div>
                <div id="error"></div>
                <button class="primary block" id="start" style="margin-top:24px">
                    학습 진단 시작하기
                </button>
                <button class="block" id="history" style="margin-top:10px">
                    지난 기록 보기
                </button>
            </div>
        `;

        const errorBox = this.querySelector('#error');
        const showMessage = (message) => {
            errorBox.className = message ? 'error-box' : '';
            errorBox.textContent = message ?? '';
        };
        if (this.dataset.error) showMessage(this.dataset.error);

        this.querySelector('#history').onclick = () => showHistoryScreen();

        let difficulty = 'medium';
        this.querySelector('#difficulty').appendChild(
            createChipGroup(DIFFICULTIES, {
                selected: difficulty,
                onSelect: (value) => {
                    difficulty = value;
                },
            })
        );

        const school = this.querySelector('#school');
        const subject = this.querySelector('#subject');
        const chapter = this.querySelector('#chapter');
        const student = this.querySelector('#student');
        const amount = this.querySelector('#amount');
        const startButton = this.querySelector('#start');

        let chapters = {};
        const onSchoolChange = () => {
            fillSelect(subject, Object.keys(chapters[school.value] ?? {}));
            onSubjectChange();
        };
        const onSubjectChange = () => {
            fillSelect(chapter, chapters[school.value]?.[subject.value] ?? []);
        };
        school.onchange = onSchoolChange;
        subject.onchange = onSubjectChange;

        startButton.disabled = true;
        try {
            chapters = await api.chapters();
            fillSelect(school, Object.keys(chapters));
            onSchoolChange();
            startButton.disabled = false;
        } catch (err) {
            showMessage(`단원 목록을 불러오지 못했습니다. ${err.message}`);
            return;
        }

        const submit = () => {
            if (!chapter.value) {
                showMessage('과목과 단원을 선택해 주세요.');
                return;
            }
            startQuiz(
                {
                    student: student.value.trim() || '학생',
                    school: school.value,
                    subject: subject.value,
                    chapter: chapter.value,
                    difficulty,
                },
                Math.min(Math.max(Number(amount.value) || 5, 1), 20)
            );
        };

        startButton.onclick = submit;
        student.addEventListener('keydown', (event) => {
            if (event.key === 'Enter') submit();
        });
    }
}

customElements.define('option-page', OptionPage);