from typing import Optional
from datetime import datetime
import re
from pydantic import BaseModel, validator

class Book(BaseModel):
    title: str
    author: str
    description: Optional[str] = None
    page_count: int
    published_date: datetime
    isbn: str

    @validator('isbn')
    def validate_isbn(cls, isbn):
        """
        Validate the ISBN format.
        """
        pattern = r'^[\d-]+$'
        if not re.match(pattern, isbn):
            raise ValueError('Invalid ISBN format')
        return isbn

def create_book(db, book_data):
    """
    Create a new book in the database.

    Args:
        db: Database session
        book_data: Book data to create

    Returns:
        Book object if created successfully, None otherwise
    """
    try:
        book = Book(**book_data.dict())
    except ValueError as e:
        return None

    db_book = db.query(Book).filter(Book.isbn == book.isbn).first()
    if db_book:
        return None

    db.add(book)
    db.commit()
    db.refresh(book)
    return book

def get_book_by_isbn(db, isbn):
    """
    Get a book by its ISBN.

    Args:
        db: Database session
        isbn: ISBN to search for

    Returns:
        Book object if found, None otherwise
    """
    return db.query(Book).filter(Book.isbn == isbn).first()

def search_books(db, query):
    """
    Search for books based on a query string.

    Args:
        db: Database session
        query: Search query string

    Returns:
        List of Book objects matching the query
    """
    books = db.query(Book).filter(
        Book.title.ilike(f'%{query}%') |
        Book.author.ilike(f'%{query}%') |
        Book.description.ilike(f'%{query}%')
    ).all()
    return books