from typing import List, Optional
from datetime import datetime
from pydantic import BaseModel
from sqlalchemy.orm import Session
from models.book import Book
from schemas.book import BookCreate, BookUpdate

def get_books(db: Session, skip: int = 0, limit: int = 100) -> List[Book]:
    """
    Retrieve a list of books from the database.

    Args:
        db (Session): SQLAlchemy database session
        skip (int, optional): Number of books to skip. Defaults to 0.
        limit (int, optional): Maximum number of books to return. Defaults to 100.

    Returns:
        List[Book]: List of Book objects
    """
    return db.query(Book).offset(skip).limit(limit).all()

def get_book_by_id(db: Session, book_id: int) -> Optional[Book]:
    """
    Retrieve a book by its ID from the database.

    Args:
        db (Session): SQLAlchemy database session
        book_id (int): ID of the book to retrieve

    Returns:
        Optional[Book]: Book object if found, None otherwise
    """
    return db.query(Book).filter(Book.id == book_id).first()

def create_book(db: Session, book: BookCreate) -> Book:
    """
    Create a new book in the database.

    Args:
        db (Session): SQLAlchemy database session
        book (BookCreate): Book data to create

    Returns:
        Book: Created Book object
    """
    db_book = Book(**book.dict())
    db.add(db_book)
    db.commit()
    db.refresh(db_book)
    return db_book

def update_book(db: Session, book_id: int, book_data: BookUpdate) -> Optional[Book]:
    """
    Update an existing book in the database.

    Args:
        db (Session): SQLAlchemy database session
        book_id (int): ID of the book to update
        book_data (BookUpdate): Updated book data

    Returns:
        Optional[Book]: Updated Book object if found, None otherwise
    """
    db_book = db.query(Book).filter(Book.id == book_id).first()
    if not db_book:
        return None

    for field, value in book_data.dict(exclude_unset=True).items():
        setattr(db_book, field, value)

    db.commit()
    db.refresh(db_book)
    return db_book

def delete_book(db: Session, book_id: int) -> bool:
    """
    Delete a book from the database.

    Args:
        db (Session): SQLAlchemy database session
        book_id (int): ID of the book to delete

    Returns:
        bool: True if the book was deleted, False otherwise
    """
    db_book = db.query(Book).filter(Book.id == book_id).first()
    if not db_book:
        return False

    db.delete(db_book)
    db.commit()
    return True