backend/controller/holidays.js

const { google } = require('googleapis');
const { oAuth2Client } = require('../config/googleOAuth');
const { checkAndRefreshAccessToken } = require('../utils/refreshToken');

let holidays = [];
let allHolidayDates = [];

async function getIndiaTamilHolidays() {
    try {
        const userTokens = await checkAndRefreshAccessToken();

        // Check if OAuth tokens are available
        if (!userTokens || !userTokens.access_token) {
            console.log("OAuth credentials missing. Please authorize the app first.");
            return { error: 'OAuth credentials missing. Please authorize the app first.' };
        }

        // Set OAuth2 credentials
        oAuth2Client.setCredentials(userTokens);

        // Initialize Google Calendar API
        const calendar = google.calendar({ version: 'v3', auth: oAuth2Client });

        // Define the Indian Holidays calendar ID and time range
        // const calendarId = 'en.indian#[email protected]';
        const calendarId = '[email protected]'; //Tamil Nadu  holidays
        const currentYear = new Date().getFullYear(); //works in Indian server only mostly I guess
        const timeMin = `${currentYear}-01-01T00:00:00Z`;
        const timeMax = `${currentYear + 50}-12-31T23:59:59Z`;

        // Fetch holiday events
        const response = await calendar.events.list({
            calendarId,
            timeMin,
            timeMax,
            singleEvents: true,
            orderBy: 'startTime',
        });

        // Extract and format holiday details
        const holidays = [];
        response.data.items.forEach(event => {
            const summary = event.summary;
            const startDate = event.start.date;
            const endDate = event.end?.date || event.start.date;
        
            // Handle single-day or multi-day holidays
            const start = new Date(startDate);
            const end = new Date(endDate);
        
            // Iterate through all dates for multi-day holidays
            for (let d = new Date(start); d < end; d.setDate(d.getDate() + 1)) {
                console.log('Holiday:', summary, d);
                holidays.push({
                    festival: summary,
                    date: d.toISOString().split('T')[0], // Format date as YYYY-MM-DD
                });
            }
        });                

        return holidays;
    } catch (error) {
        console.error('Error fetching India holidays:', error.message);
        throw error;
    }
}

// Call the function to get tamil holidays
async function refreshHolidays() {
    try {
        holidays = await getIndiaTamilHolidays();  // Fetch the holidays
        console.log('India Holidays:', holidays);
        console.log('Total holidays:', holidays.length);
        console.log('Last holiday:', holidays[holidays.length - 1]);

        allHolidayDates = holidays.reduce((accumulator, holiday) => {
            accumulator.push(holiday.date);  // Collect all dates in an array
            return accumulator;
        }, []);
        
        console.log(allHolidayDates); 

        // After the function finishes, set the next interval
        setTimeout(refreshHolidays, 14 * 24 * 60 * 60 * 1000);  // 14 days in ms
    } catch (error) {
        console.error('Failed to fetch holidays:', error);

        // If there's an error, retry after a short delay
        setTimeout(refreshHolidays, 10000); // Retry in 10 seconds
    }
}

async function isHoliday(date) {
    return allHolidayDates.includes(date);
}

module.exports = { getIndiaTamilHolidays, refreshHolidays, isHoliday };