lab/library/library.py

python

from library.models import Book, Member

MAX_BOOKS_PER_MEMBER = 3

class BookNotAvailableError(Exception):

    """Raised when a book is already issued to someone."""

class Library:

    def __init__(self) -> None:

        self.books: dict[str, Book] = {}

        self.members: dict[str, Member] = {}

    def add_book(self, book: Book) -> None:

        if book.isbn in self.books:

            raise ValueError(f"Duplicate ISBN {book.isbn}")

        self.books[book.isbn] = book

    def add_member(self, member: Member) -> None:

        self.members[member.member_id] = member

    def issue_book(self, isbn: str, member_id: str) -> None:

        book = self.books[isbn]

        member = self.members[member_id]

        if not book.available:

            raise BookNotAvailableError(f"'{book.title}' is issued to {book.issued_to}")

        if len(member.borrowed) >= MAX_BOOKS_PER_MEMBER:

            raise ValueError(f"{member.name} already has {MAX_BOOKS_PER_MEMBER} books")

        book.issued_to = member_id

        member.borrowed.append(isbn)

    def return_book(self, isbn: str) -> None:

        book = self.books[isbn]

        if book.available:

            raise ValueError(f"'{book.title}' is not issued")

        self.members[book.issued_to].borrowed.remove(isbn)

        book.issued_to = None

    def search(self, query: str) -> list[Book]:

        q = query.lower()

        return [b for b in self.books.values() if q in b.title.lower() or q in b.author.lower()]