function checkoutBook(bookId, userId) {
    // Check if the book is available
    Book.findByPk(bookId).then(book => {
        if (book.status === 'Available') {
            // If available, create a new Checkout record
            Checkout.create({ book_id: bookId, user_id: userId }).then(checkout => {
                // Update the Book status to 'Checked Out'
                book.update({ status: 'Checked Out' }).then(() => {
                    // Return the Checkout record
                    return checkout;
                });
            });
        } else {
            // If the book is not available, return null
            return null;
        }
    });
}

function returnBook(bookId) {
    // Find the Checkout record for the book
    Checkout.findOne({ where: { book_id: bookId, returned_date: null } }).then(checkout => {
        if (checkout) {
            // Update the Checkout record with the returned date
            checkout.update({ returned_date: new Date() }).then(() => {
                // Update the Book status to 'Available'
                Book.findByPk(bookId).then(book => {
                    book.update({ status: 'Available' });
                });
            });
        }
    });
}

function formatOpenLibraryData(data) {
    return {
        isbn: data.identifiers.isbn_13 ? data.identifiers.isbn_13[0] : '',
        title: data.title,
        authors: data.authors ? data.authors.map(author => author.name) : [],
        publishedDate: data.publish_date,
        description: data.excerpts ? data.excerpts[0].text : 'No description available',
        url: data.url,
        number_of_pages: data.number_of_pages || null,
        identifiers: JSON.stringify(data.identifiers), // Store as JSON string
        publishers: data.publishers ? data.publishers.map(pub => pub.name).join(', ') : '',
        subjects: data.subjects ? data.subjects.map(sub => sub.name).join(', ') : '',
        notes: data.notes || '',
        cover_small: data.cover ? data.cover.small : '',
        cover_medium: data.cover ? data.cover.medium : '',
        cover_large: data.cover ? data.cover.large : ''
    };
}


function formatArchiveData(data) {
    return {
        isbn: data.isbn ? data.isbn[0] : '',
        title: data.title,
        authors: data.contributor ? [data.contributor] : [],
        publishedDate: data.date ? new Date(data.date).getFullYear() : '',
        description: data.description ? data.description.join(' ') : 'No description available',
        url: `https://archive.org/details/${data.identifier}`,
        number_of_pages: data.imagecount || null,
        identifiers: JSON.stringify({
            archive_identifier: data.identifier,
            oclc: data['external-identifier'] ? data['external-identifier'].filter(id => id.includes('urn:oclc')).map(id => id.split(':')[2]) : []
        }),
        publishers: data.publisher || '',
        subjects: data.subject ? data.subject.join(', ') : '',
        notes: '', // Archive data does not provide specific notes like Open Library
        cover_small: '', // Placeholder, as cover image URLs need to be constructed manually
        cover_medium: '', // Same as above
        cover_large: ''  // Same as above
    };
}

function formatGoogleBooksData(data) {
    return {
        isbn: data.volumeInfo.industryIdentifiers ? data.volumeInfo.industryIdentifiers.find(id => id.type === 'ISBN_13').identifier : '',
        title: data.volumeInfo.title,
        authors: data.volumeInfo.authors || [],
        publishedDate: data.volumeInfo.publishedDate,
        description: data.volumeInfo.description || 'No description available',
        url: data.volumeInfo.previewLink,
        number_of_pages: data.volumeInfo.pageCount || null,
        identifiers: JSON.stringify(data.volumeInfo.industryIdentifiers),
        publishers: data.volumeInfo.publisher || '',
        subjects: data.volumeInfo.categories || [],
        notes: '', // Placeholder for additional notes
        cover_small: data.volumeInfo.imageLinks.smallThumbnail || '',
        cover_medium: data.volumeInfo.imageLinks.thumbnail || '',
        cover_large: data.volumeInfo.imageLinks.small || ''
    };
}


module.exports = {
    checkoutBook,
    returnBook,
    formatOpenLibraryData,
    formatArchiveData,
    formatGoogleBooksData
};