User: Task: "Create Implement Waitlist Feature Api"
    Description: "Generate a Node.js Waitlist Feature Api with given dependenceis"
    Requirements:
    - Database: mongoose
    - Authentication: None specified
    - Output needed: Return only the function code as specified in dependencies
    - Dependencies: Create a Api to add a user to the waitlist for a fully booked date. Export: exports.addToWaitlist = async () => {...}, 
Accept parameters: userId, checkInDate, checkOutDate, roomId., 
Validate required fields: Ensure userId, checkInDate, checkOutDate, and roomId are provided., 
If the requested date is fully booked, add the user to the waitlist for that date., 
Store waitlist data with date, roomId, userId, and priority level., 
When a booking is canceled, notify users on the waitlist and offer the available slot., 
Respond to user with a success message confirming the user has been added to the waitlist., 
Handle errors like invalid dates, conflicting bookings, or database issues.
    - Previous Code 
const mongoose = require('mongoose');
// Importing the Booking model (assuming it has been defined elsewhere in your code)
const Booking = require('./models/Booking');

// Function to check availability of a room or service
exports.checkAvailability = async (checkInDate, checkOutDate, roomId) => {
    // Validate required fields
    if (!checkInDate || !checkOutDate || !roomId) {
        throw new Error('Missing required parameters: checkInDate, checkOutDate, and roomId are required.');
    }

    try {
        // Convert dates to appropriate format if needed (for example, using new Date())
        const checkIn = new Date(checkInDate);
        const checkOut = new Date(checkOutDate);

        // Query the Booking model to check for existing bookings during the specified date range
        const existingBooking = await Booking.findOne({
            roomId: roomId,
            $or: [
                { checkInDate: { $lt: checkOut }, checkOutDate: { $gt: checkIn } },
                { checkInDate: { $eq: checkIn }, checkOutDate: { $eq: checkOut } }
            ]
        });

        // If a booking already exists in the date range, indicate double booking
        if (existingBooking) {
            return {
                success: false,
                message: 'The room or service is unavailable for the selected date range due to a double booking.'
            };
        }

        // If no booking exists, indicate that the room or service is available
        return {
            success: true,
            message: 'The room or service is available for booking.'
        };
    } catch (error) {
        // Handle errors such as database connection errors
        console.error('Error checking availability:', error);
        throw new Error(`Error checking availability: ${error.message}`);
    }
};

// Function to manage time slots
exports.manageTimeSlots = async (date, serviceId, availableSlots) => {
    // Validate required fields
    if (!date || !serviceId || !Array.isArray(availableSlots) || availableSlots.length === 0) {
        throw new Error('Missing required parameters: date, serviceId, and availableSlots are required.');
    }

    try {
        // Ensure date is a valid date
        const slotDate = new Date(date);
        if (isNaN(slotDate)) {
            throw new Error('Invalid date provided.');
        }

        // Check for overlapping bookings
        const overlappingBookings = await Booking.find({
            serviceId: serviceId,
            $or: availableSlots.map(slot => ({
                date: slotDate,
                time: { $eq: slot } // Assuming Booking has a 'time' field
            }))
        });

        if (overlappingBookings.length > 0) {
            throw new Error('Some of the time slots overlap with existing bookings.');
        }

        // Update or create time slots for the given date and service
        for (let slot of availableSlots) {
            await TimeSlot.updateOne(
                { date: slotDate, serviceId: serviceId, time: slot },
                { $set: { available: true } }, // Assuming TimeSlot has an 'available' field
                { upsert: true } // Creates a new document if no match is found
            );
        }

        return {
            success: true,
            message: 'Available time slots have been successfully updated.'
        };

    } catch (error) {
        // Handle errors such as invalid date, overlapping time slots, or database issues
        console.error('Error managing time slots:', error);
        throw new Error(`Error managing time slots: ${error.message}`);
    }
};

// Function to create recurring bookings
exports.createRecurringBooking = async (startDate, endDate, frequency, roomId) => {
    try {
        // Validate required fields
        if (!startDate || !endDate || !frequency || !roomId) {
            throw new Error('Missing required parameters: startDate, endDate, frequency, and roomId are required.');
        }

        // Convert dates to appropriate format
        const start = new Date(startDate);
        const end = new Date(endDate);
        if (isNaN(start) || isNaN(end)) {
            throw new Error('Invalid dates provided.');
        }

        // Define the logic to schedule recurring dates based on frequency
        const recurringDates = [];
        let current = new Date(start);

        while (current <= end) {
            recurringDates.push(new Date(current));
            if (frequency.toLowerCase() === 'weekly') {
                current.setDate(current.getDate() + 7);
            } else if (frequency.toLowerCase() === 'monthly') {
                current.setMonth(current.getMonth() + 1);
            } else {
                throw new Error('Invalid frequency provided. Only "weekly" and "monthly" are supported.');
            }
        }

        // Create bookings for each recurring date
        const bookingDetails = [];
        for (const date of recurringDates) {
            const availability = await exports.checkAvailability(date, date, roomId);
            if (!availability.success) {
                throw new Error(`Conflict: ${availability.message}`);
            }

            // Create the booking (assuming Booking model has schema fields required)
            const booking = new Booking({
                roomId: roomId,
                checkInDate: date,
                checkOutDate: date,
                status: 'Booked'
                // Add more fields as necessary
            });

            await booking.save();
            bookingDetails.push({ date: date, bookingId: booking._id });
        }

        // Respond with success message
        return {
            success: true,
            message: 'Recurring bookings created successfully.',
            bookings: bookingDetails
        };

    } catch (error) {
        // Handle errors such as conflicting bookings, invalid parameters, or database issues
        console.error('Error creating recurring bookings:', error);
        throw new Error(`Error creating recurring bookings: ${error.message}`);
    }
};

    - Supporting data 
    - Updating File undefined
    
    Please generate the code for this task, following the instructions and including comments for clarity.
    While creating router for specifict file your have to read supporing file data and create for that 

    **Output Formats**: 

Return dependencies like this `const bcrypt = require('bcrypt');`  in this formate
```dependencies
const bcrypt = require('bcrypt');
```

Ensure this format is consistently followed in responses.
    
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