Untitled

class Library{
    List<Book>books;
    List<Patron>patrons;
    List<Activity> checkoutReturnHistory;

    addPatron(Patron){
        //...
    }
    searchBook(Book.title, Book.author, Book.isbn){
        //..
    }
    checkoutBook(Patron, Book){
        //..
    }
    returnBook(Book){
        //...
    }
    displayBooks(){
        //..
    }
    getPatrons(){
        //..
    }
    displayBooksCheckedout(){
        //..
    }
    generateUsageReport(){
        //..
    }
}

class Book{
    string title;
    string author;
    string isbn;

    string bookId;
    boolean isCheckedOut;
    DateTime toBeReturnedOn;
    string currentPatronId;

    getBookDetails(){
        //..
    }

    checkout(patronId){
        //..
    }

    return(){
        //..
    }

    getCheckoutDetails(){
        //..
    }
}

class Patron{
    string patronId;
    string name;
    List<String> currentBookIds;

    checkoutBook(bookId){
        //..
    }
    returnBook(bookId){
        //..
    }

    getDetails(){
        //..
    }

}

class Activity{
    string activityId;
    ActivityType activityType;
    string patron;
    string bookId;
}

enum ActivityType{
    CHECKOUT, RETURN
}