Description

Flipkart is taking initiatives in opening a chain of libraries. It is initially starting a library in Bangalore. Based on the response, it may take this initiative further. You need to create a backend system to maintain the functionality of the library.

The users can register and take membership of the library for a certain period of time.
There are n different books available in the library and each book having a certain number of copies.
A registered user with active membership can borrow a book from the library.
A user can hold upto 2 books at a time.
One user can not hold two copies of the same book together.
A book has to be returned within 30 days or before the membership end date, whichever is earlier.
A user can return the book at any point of time. Beyond the due_date, a fine of Rs 1 is applied for a day.
A user can view his/her current details along with the book history borrowed by him/her.
A user can check the list of available books.

Bonus
Implement a system where a user can donate book(s) to extend his/her library membership validity. Consider that donating a book will extend the membership by 90 days.

For simplicity, assume that the initial inventory is already present in the system.

Application Functionalities

REGISTER user_id user_name start_date end_date
Output: Show message for successful/failed registration
BORROW user_id book_id issue_date
Output: book_id, book_name, author_name, issue_date, due_date
RETURN user_id book_id return_date
Output: book_id, due_date, return_date, fine amount
VIEW user_id
Output: user details; Issue History: book_id, book_name, issue_date, due_date, return_date; membership start and end date
SHOW_INVENTORY
Output: List<book_name, author_name, current count>
[Bonus]
DONATE user_id book_name author_name
Output: book_id, count in the inventory, extended membership end_date of user

Test cases
REGISTER suraj123 suraj 2021-12-04 2022-12-04
Output: User with id suraj123 registered successfully.
SHOW_INVENTORY
Output:
Id: 1, Name: Algorithms, Author: Cormen, Count: 5
Id: 2, Name: Nursery Rhymes, Author: Peter, Count: 1
BORROW suraj123 1 2021-12-04
Output-
book_id: 1, book_name: Algorithms, author: Cormen, issue_date: 2021-12-04, due_date: 2022-01-03
SHOW_INVENTORY
Output:
Id: 1, Name: Algorithms, Author: Cormen, Count: 4
Id: 2, Name: Nursery Rhymes, Author: Peter, Count: 1
VIEW suraj123
Output:
Name: suraj, Id: suraj123
Issue History-
- book_id: 1, book_name: Algorithms, author: Cormen, issue_date: 2021-12-04, due_date: 2022-01-04, return_date: null, fine amount: 0
Membership details- start_date: 2021-12-04, end_date: 2022-12-04
RETURN suraj123 1 2021-12-02
Output: Invalid input. Return date should be after issue date.
RETURN suraj123 1 2022-01-10
Output: book_id: 1, due_date: 2022-01-03, fine_amount: 7
SHOW_INVENTORY
Output:
Id: 1, Name: Algorithms, Author: Cormen, Count: 5
Id: 2, Name: Nursery Rhymes, Author: Peter, Count: 1
[Bonus]
DONATE suraj123 Sherlock Doyle
Output- book_id: 3, Membership end_date extended to: 2023-03-04
SHOW_INVENTORY
Output:
Id: 1, Name: Algorithms, Author: Cormen, Count: 5
Id: 2, Name: Nursery Rhymes, Author: Peter, Count: 1
Id: 3, Name: Sherlock, Author: Doyle, Count: 1
VIEW suraj123
Output:
Name: suraj, Id: suraj123
Issue History-
- book_id: 1, book_name: Algorithms, author: Cormen, issue_date: 2021-12-04, due_date: 2022-01-04, return_date: 2022-01-10, fine amount: 7
Membership details- start_date: 2021-12-04, end_date: 2023-03-04

Things to take care of:

Do not use any database or NoSQL store, use in-memory store for now.
Do not create any UI for the application.
Write a driver class for demo purposes. Which will execute all the commands at one place in the code and test cases.
Please prioritize code compilation, execution and completion.
Please do not access the internet for anything EXCEPT syntax.
You are free to use the language of your choice.
All work should be your own. If found otherwise, you may be disqualified.

Expectations:
Code should be demoable (very important)
Complete coding within the duration of 90 minutes.
Prefer Design over optimization. Better design would be considered better.
Code should be modular, with an Object Oriented design. Maintain good separation of concerns.
Code should be extensible. It should be easy to add/remove functionality without rewriting the entire codebase.
Code should handle edge cases properly and fail gracefully.
Code should be readable. Follow good coding practices:
Use intuitive variable names, function names, class names etc.
Indent code properly.