// ==UserScript==
// @name         UBC Workday Calendar Generator
// @namespace    http://tampermonkey.net/
// @version      1.6
// @description  Adds a 'Download Calendar (.ics)' button to the Workday popup list and generates ICS file with recurring events
// @match        *://*.myworkday.com/ubc*
// @author       TU
// @license      TU
// @grant        none
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict';

    const timeZone = 'America/Vancouver'; // Kelowna's timezone

    function formatToICS(event, courseNameCal, courseTypeCal, uniqueId) {
        const crlf = '\r\n';

        function convertTime(time) {
            const match = time.match(/(\d+):(\d+)\s*(a\.m\.|p\.m\.)/i);
            if (!match) return '';

            let [_, hours, minutes, period] = match;
            let hours24 = parseInt(hours, 10);
            if (period.toLowerCase() === 'p.m.' && hours24 !== 12) {
                hours24 += 12;
            } else if (period.toLowerCase() === 'a.m.' && hours24 === 12) {
                hours24 = 0;
            }
            return `${hours24.toString().padStart(2, '0')}${minutes.padStart(2, '0')}00`;
        }

        const startTime = convertTime(event.startTime);
        const endTime = convertTime(event.endTime);

        const dtstamp = new Date().toISOString().replace(/[-:]/g, '').split('.')[0] + 'Z'; // UTC format
        const uid = `${uniqueId}-${event.startDate}@tupreti.com`; // Unique UID
        const startDate = event.startDate.replace(/-/g, ''); // Format to YYYYMMDD

        // Construct RRULE for recurring events
        const dayMap = { Mon: 'MO', Tue: 'TU', Wed: 'WE', Thu: 'TH', Fri: 'FR', Sat: 'SA', Sun: 'SU' };
        const days = event.days.split(' ').map(day => dayMap[day]).join(',');
        const frequency = `FREQ=WEEKLY;BYDAY=${days}`;
        const recurrenceRule = event.alternateWeeks
            ? `${frequency};INTERVAL=2;UNTIL=${event.endDate.replace(/-/g, '')}T235959Z`
            : `${frequency};UNTIL=${event.endDate.replace(/-/g, '')}T235959Z`;

        // Construct the ICS event
        const icsEvent = `BEGIN:VEVENT${crlf}` +
                         `UID:${uid}${crlf}` +
                         `DTSTAMP:${dtstamp}${crlf}` +
                         `DTSTART;TZID=${timeZone}:${startDate}T${startTime}${crlf}` +
                         `DTEND;TZID=${timeZone}:${startDate}T${endTime}${crlf}` +
                         `RRULE:${recurrenceRule}${crlf}` +
                         `SUMMARY:${courseNameCal || 'No Title'}${crlf}` +
                         `DESCRIPTION:${courseTypeCal || 'No Description'}${crlf}` +
                         `LOCATION:${event.location || 'No Location'}${crlf}` +
                         `END:VEVENT`;

        return icsEvent;
    }

    function generateICSFile(events) {
        const crlf = '\r\n';
        const icsContent = `BEGIN:VCALENDAR${crlf}` +
                           `VERSION:2.0${crlf}` +
                           `PRODID:-//Tanish Upreti//UBC Workday Calendar Generator//EN${crlf}` +
                           `CALSCALE:GREGORIAN${crlf}` +
                           `METHOD:PUBLISH${crlf}` +
                           `X-WR-TIMEZONE:${timeZone}${crlf}` +
                           events.join(crlf) +
                           crlf + `END:VCALENDAR`;

        const blob = new Blob([icsContent], { type: 'text/calendar' });
        const url = URL.createObjectURL(blob);

        const a = document.createElement('a');
        a.href = url;
        a.download = 'UBC Course Schedule.ics';
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        URL.revokeObjectURL(url);
    }

    function processMeetingPattern(meetingPattern) {
        let [dateRange, daysAndWeeks, timeRange, location] = meetingPattern.split(" | ");
        let [startDate, endDate] = dateRange.split(" - ");
        let alternateWeeks = daysAndWeeks.includes("(Alternate weeks)");
        let days = alternateWeeks ? daysAndWeeks.replace("(Alternate weeks)", "").trim() : daysAndWeeks.trim();
        let [startTime, endTime] = timeRange.split(" - ");

        return {
            startDate,
            endDate,
            days,
            alternateWeeks,
            startTime,
            endTime,
            location
        };
    }

    function extractAllCourseNamesAndGenerateICS() {
        console.log("ICS generation triggered");

        requestIdleCallback(() => {
            try {
                const divs = document.querySelectorAll('div[data-automation-label]');
                const courseNames = [];

                divs.forEach(div => {
                    const courseName = div.getAttribute('data-automation-label');
                    if (courseName) {
                        courseNames.push(courseName);
                    }
                });

                const pattern = /\b[A-Z]{3,4}_O \d{3}-[A-Z0-9]{1,4} - .+/;

                const events = [];
                for (let i = 0; i < courseNames.length; i++) {
                    const currentItem = courseNames[i];
                    if (pattern.test(currentItem)) {
                        const course = currentItem;
                        const instructionalFormat = courseNames[i + 1];

                        let j = i + 3;
                        while (j < courseNames.length && courseNames[j].includes('|')) {
                            const meetingPatterns = courseNames[j];
                            const parsed = processMeetingPattern(meetingPatterns);
                            const event = formatToICS(parsed, course, instructionalFormat, i);
                            events.push(event);

                            j++;
                        }

                        i = j - 1;
                    }
                }

                if (events.length > 0) {
                    generateICSFile(events);
                } else {
                    console.log("No events found to generate.");
                }
            } catch (error) {
                console.error("Error while extracting course names and generating ICS:", error);
            }
        });
    }

    function addCalendarDownloadButton() {
        const selectedTab = document.querySelector('li[data-automation-id="selectedTab"]');
        if (selectedTab && selectedTab.querySelector('div[data-automation-id="tabLabel"]').textContent.trim() === 'Registration & Courses') {
            const popups = document.querySelectorAll('div[data-automation-id="workletPopup"]');
            popups.forEach(popup => {
                const menuList = popup.querySelector('ul[data-automation-id="menuList"]');
                if (menuList && !menuList.querySelector('div[data-automation-id="calendarDownloadButton"]')) {
                    console.log("Menu list detected, adding 'Download Calendar (.ics)' button.");

                    const existingListItem = menuList.querySelector('li');
                    if (existingListItem) {
                        const newListItem = existingListItem.cloneNode(true);
                        const newButtonDiv = newListItem.querySelector('div').cloneNode(true);
                        newListItem.replaceChild(newButtonDiv, newListItem.querySelector('div'));

                        newButtonDiv.textContent = 'Download Calendar (.ics)';
                        newButtonDiv.setAttribute('data-automation-id', 'calendarDownloadButton');
                        newButtonDiv.setAttribute('aria-label', 'Download Calendar');
                        newButtonDiv.addEventListener('click', extractAllCourseNamesAndGenerateICS);

                        menuList.appendChild(newListItem);
                    }
                }
            });
        }
    }

    const observer = new MutationObserver(() => {
        addCalendarDownloadButton();
    });

    observer.observe(document, { childList: true, subtree: true });
})();