/* Functions */
function openNewTabWithHTML(htmlContent) {
    const newTab = window.open("", "_blank");
    newTab.document.write(htmlContent);
    newTab.document.close();
};

function fetchUrlContent(url, callback) {
    fetch(url)
        .then(response => {
            if (!response.ok) {
                throw new Error(`HTTP error! Status: ${response.status}`);
            }
            return response.text();
        })
        .then(data => callback(null, data))
        .catch(error => {
            console.error('Fetch error: ', error);
            callback(error, "");
        });
};

function formatDate(dateStr) {
    return new Date(dateStr).toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
}

function formatDateReadable(dateStr) {
    return new Date(dateStr).toDateString();
}


function jsonToIcal(data) {
    if (!data.start || !data.end || !data.title || !data.id) {
        alert("Required fields missing from input data.");
        throw new Error("Required fields missing from input data.");
    }

    let icalStr = 'BEGIN:VCALENDAR\nVERSION:1.0\nPRODID:-//42Cal//\n';
    icalStr += 'BEGIN:VEVENT\n';

    icalStr += `UID:${data.id}\n`;
    icalStr += `SUMMARY:${data.title}\n`;
    icalStr += `DESCRIPTION:${`DURATION: ${data.duration}\\n\\n` + data.description.trim()}\n`;
    icalStr += `LOCATION:${data.location}\n`;
    icalStr += `DTSTART:${formatDate(data.start)}\n`;
    icalStr += `DTEND:${formatDate(data.end)}\n`;

    icalStr += 'END:VEVENT\n';
    icalStr += 'END:VCALENDAR';

    return icalStr;
};

function addExtraData(event, callback) {
    let kind = 'events';
    if (event.kind === 'exam')
    {
        kind = 'exams';
    }
    fetchUrlContent(`https://profile.intra.42.fr/${kind}/${event.id}`, (error, data) => {
        if (error) {
            alert('Error2: ' + error);
            console.log('Error2: ' + error);
            callback();
        } else {
            parser = new DOMParser();
            doc = parser.parseFromString(data, "text/html");
            const description = doc.querySelector('.notification-text').textContent;
            const duration = doc.querySelector('.icon-clock')?.parentElement.children[2].textContent;
            const _location = doc.querySelector('.icon-location')?.parentElement.children[1].textContent;
            if (description)
                event.description = description;
            else
                event.description = 'Could not fetch description';
            if (duration)
                event.duration = duration;
            else
                event.duration = 'Could not fetch duration';
            if (_location)
                event.location = _location;
            else
                event.location = 'Could not fetch location';
            callback(event)
        }
    });
}

function eventsToHtml(events) {
    let htmlString = '<h1>Download iCals</h1><ol>';
    events.sort((a,b) => new Date(a.start) - new Date(b.start)).forEach(event => {
        const icalString = jsonToIcal(event);
        const base64Data = btoa(unescape(encodeURIComponent(icalString)));
        const fileName = event.title ? event.title.replace(/\s+/g, '_') + '.ics' : `event_${index + 1}.ics`;
        const date_formatted = formatDateReadable(event.start);

        htmlString += `<li>
            <a href="data:text/calendar;base64,${base64Data}" download="${fileName}">
                <button style="background-color: ${event.is_subscribed ? 'lightgreen' : 'rgb(239, 239, 239)'}; ">
                    ${date_formatted}: Download '<span style="color: #1443d3; font-weight: bold; ">${event.title || 'Event'}.ical</span>'
                </button>
            </a>
        </li>`;
    });
    htmlString += '</ol>';
    return htmlString;
}

function generateDownloadPage(dataList, only_subscribed_events) {

    const promises = dataList.map((event, index) => {
        return new Promise((resolve, reject) => {
            if (!event.id || !event.title || !event.end || !event.start) {
                resolve();
                return;
            }

            if (only_subscribed_events && !event.is_subscribed) {
                resolve();
                return;
            }

            addExtraData(event, event => {
                resolve(event);
            });
        });
    });

    return Promise.all(promises)
    .then(events => {
        return eventsToHtml(events.filter(Boolean));
    });
};

function generateApiDateParams() {
    const currentDate = new Date();
    const year = currentDate.getFullYear();
    const nextYear = year + 1;
    const month = String(currentDate.getMonth() + 1).padStart(2, '0');
    const day = String(currentDate.getDate()).padStart(2, '0');
    const formattedDateStart = `${year}-${month}-${day}`;
    const formattedDateEnd = `${nextYear}-${month}-${day}`;

    return `start=${formattedDateStart}&end=${formattedDateEnd}`
};

function open_upcoming_events_new_tab(only_subscribed_events) {
    fetchUrlContent(`https://profile.intra.42.fr/events.json?${generateApiDateParams()}`, (error, data) => {
        if (error) {
            alert('Error: ' + error);
        } else {
            generateDownloadPage(JSON.parse(data), only_subscribed_events)
            .then(html => {
                openNewTabWithHTML(html)
            })
            .catch(error => {
                alert("Error1: " + error);
            }
            );
        }
    });
}
/* End Functions */

open_upcoming_events_new_tab(false);