document.addEventListener('DOMContentLoaded', () => {
    const dateElement = document.getElementById('current-date');
    const eventsList = document.getElementById('events-list');
    const timeCommentElement = document.getElementById('time-comment');
    const prevBtn = document.getElementById('prev-btn');
    const nextBtn = document.getElementById('next-btn');


    const dialog = document.getElementById('date-dialog');
    const datePickerInput = document.getElementById('date-picker-input');
    const cancelDateBtn = document.getElementById('cancel-date-btn');
    const confirmDateBtn = document.getElementById('confirm-date-btn');


    let currentDate;
    const urlParams = new URLSearchParams(window.location.search);
    const yearParam = urlParams.get("year");
    const monthParam = urlParams.get("month");
    const dayParam = urlParams.get("day");


    if (yearParam && monthParam && dayParam) {
        currentDate = new Date(parseInt(yearParam), parseInt(monthParam) - 1, parseInt(dayParam));
    } else {
        currentDate = new Date();
    }


    fetchAndRender(currentDate);

    function fetchAndRender(date) {

        const year = date.getFullYear();
        const month = date.getMonth() + 1;
        const day = date.getDate();

        const newUrl = `?year=${year}&month=${month}&day=${day}`;
        window.history.pushState({ path: newUrl }, '', newUrl);


        const options = { year: 'numeric', month: 'long', day: 'numeric' };
        dateElement.textContent = date.toLocaleDateString('zh-TW', options);


        eventsList.innerHTML = '<p>正在載入歷史事件...</p>';
        timeCommentElement.classList.add('hide');


        const requestURL = `/api/query?year=${year}&month=${month}&day=${day}`;

        fetch(requestURL)
            .then(response => {
                if (!response.ok) throw new Error("Network response was not ok");
                return response.json();
            })
            .then(data => {
                renderEvents(data.events);
            })
            .catch(error => {
                console.error('Fetch error:', error);
                eventsList.innerHTML = '<p style="color: red;">載入歷史事件失敗。請檢查 API 連線。</p>';
            });
    }

    function renderEvents(events) {
        eventsList.innerHTML = '';

        if (!events || events.length === 0) {
            eventsList.innerHTML = '<p>這一天沒有已記載的重大事件。</p>';
            timeCommentElement.classList.add('hide');
            return;
        }

        events.forEach(event => {
            const card = document.createElement('div');
            card.className = 'event-card';

            const title = document.createElement('div');
            title.className = 'event-title';
            title.textContent = event.title;

            const yearSpan = document.createElement('span');
            yearSpan.className = 'event-year';
            yearSpan.textContent = `(${event.year} 年)`;

            const description = document.createElement('p');
            description.textContent = event.description;

            title.appendChild(yearSpan);
            card.appendChild(title);
            card.appendChild(description);
            eventsList.appendChild(card);
        });

        timeCommentElement.classList.remove('hide');
    }

    dateElement.addEventListener("wheel", (event) => {
        if (event.deltaY > 0) {
            nextBtn.click();
        } else if (event.deltaY < 0) {
            prevBtn.click();
        }
    })

    prevBtn.addEventListener('click', () => {
        currentDate.setDate(currentDate.getDate() - 1);
        fetchAndRender(currentDate);
    });

    nextBtn.addEventListener('click', () => {
        currentDate.setDate(currentDate.getDate() + 1);
        fetchAndRender(currentDate);
    });


    dateElement.addEventListener('click', () => {

        const yyyy = currentDate.getFullYear();
        const mm = String(currentDate.getMonth() + 1).padStart(2, '0');
        const dd = String(currentDate.getDate()).padStart(2, '0');

        datePickerInput.value = `${yyyy}-${mm}-${dd}`;
        dialog.showModal();
    });


    cancelDateBtn.addEventListener('click', () => {
        dialog.close();
    });

    confirmDateBtn.addEventListener('click', () => {
        const selectedValue = datePickerInput.value;
        if (selectedValue) {
            const [y, m, d] = selectedValue.split('-').map(Number);
            currentDate = new Date(y, m - 1, d);
            fetchAndRender(currentDate);
        }
        dialog.close();
    });


    dialog.addEventListener('click', (event) => {
        const rect = dialog.getBoundingClientRect();
        const isInDialog = (rect.top <= event.clientY && event.clientY <= rect.top + rect.height &&
            rect.left <= event.clientX && event.clientX <= rect.left + rect.width);
        if (!isInDialog) {
            dialog.close();
        }
    });

    dialog.addEventListener("keypress", (event) => {
        if (event.key === "Enter") {
            event.preventDefault();
            confirmDateBtn.click();
        }
    })
});