import express from 'express';
import ical from 'ical';
import fs from 'fs';
import cron from 'node-cron';
import axios from 'axios';

const app = express();
app.use(express.json());

let mergedCalendarUrl = '';

app.get('/', (req, res) => {
    res.sendFile('index.html', { root: '.' });
});

app.post('/merge', async (req, res) => {
    const { calendars } = req.body;

    try {
        //validate the input
        if (!calendars || !Array.isArray(calendars)) {
            return res.status(400).json({ error: 'Invalid input' });
        }
        // Fetch calendar data from URLs
        const promises = calendars.map((calendar) => {
            return axios.get(calendar.url)
                .then((response) => {
                    return {
                        data: response.data,
                        prefix: calendar.prefix,
                    };
                })
                .catch((error) => {
                    console.error(error);
                    return null;
                });
        });

        const results = await Promise.all(promises);
        // Filter out any failed requests
        const validResults = results.filter((result) => result !== null);

        // Parse calendar data
        const mergedCal = [];
        validResults.forEach((result) => {
            const calendar = ical.parseICS(result.data);
            Object.keys(calendar).forEach((key) => {
                const event = calendar[key];
                mergedCal.push({
                    start: event.start,
                    end: event.end,
                    summary: `${result.prefix} ${event.summary}`,
                });
            });
        });


        // Save merged calendar to file
        const filename = `merged-${Date.now()}.ics`;
        let icalString = `BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
`;
        mergedCal.forEach((event) => {
            icalString += `DTSTART:${event.start}
DTEND:${event.end}
SUMMARY:${event.summary}
END:VEVENT
`;
        });
        icalString += `END:VCALENDAR`;
        fs.writeFileSync(filename, icalString);


        // Generate a unique URL for the merged calendar
        const mergedCalendarUrl = `${req.protocol}://${req.get('host')}/${filename}`;

        res.json({ url: mergedCalendarUrl });
    } catch (error) {
        console.error(error);
        res.status(500).json({ error: 'Failed to merge calendars' });
    }
});

// Serve the merged calendar file
app.get('/:filename', (req, res) => {
    const filename = req.params.filename;
    res.setHeader('Content-Type', 'text/calendar');
    res.sendFile(filename, { root: '.' });
});

// Function to update the merged calendar
async function updateMergedCalendar(){
    try {
        // Load calendars data from file
        const calendarsFile = 'calendars.json';
        const calendars = JSON.parse(fs.readFileSync(calendarsFile, 'utf8'));
         
        // Fetch calendar data from URLs
         const promises = calendars.map((calendar) => {
            return axios.get(calendar.url)
                .then((response) => {
                    return {
                        data: response.data,
                        prefix: calendar.prefix,
                    };
                })
                .catch((error) => {
                    console.error(error);
                    return null;
                });
        });

        const results = await Promise.all(promises);
        // Filter out any failed requests
    const validResults = results.filter((result) => result !== null);

    // Parse calendar data
    const mergedCal = [];
    validResults.forEach((result) => {
        const calendar = ical.parseICS(result.data);
        Object.keys(calendar).forEach((key) => {
            const event = calendar[key];
            mergedCal.push({
                start: event.start,
                end: event.end,
                summary: `${result.prefix} ${event.summary}`,
            });
        });
    });

    // Save merged calendar to file
    const filename = `merged-${Date.now()}.ics`;
    let icalString = `BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
`;
    mergedCal.forEach((event) => {
        icalString += `DTSTART:${event.start}
DTEND:${event.end}
SUMMARY:${event.summary}
END:VEVENT
`;
    });
    icalString += `END:VCALENDAR`;
    fs.writeFileSync(filename, icalString);


    }  catch (error) {
        console.error(error);
    }
}

const refreshInterval = 60 * 60 * 1000; // 1 hour

setInterval(() => {
    // Fetch new calendar data and update the merged calendar
    updateMergedCalendar();
}, refreshInterval);

// Schedule a cron job to update the merged calendar every hour
cron.schedule('0 * * * *', () => {
    console.log('Updating merged calendar...');
    // TO DO: implement the logic to update the merged calendar
});

// Start the server
const port = 3000;
app.listen(port, () => {
    console.log(`Server started on port ${port}`);
});