from typing import List, Optional
from pydantic import BaseModel, validator
from sqlalchemy.orm import Session
from models import Dog, User

class DogCreate(BaseModel):
    name: str
    breed: str
    age: int
    owner_id: str

    @validator('name')
    def validate_name(cls, name):
        if not name.isalpha():
            raise ValueError('Name should only contain alphabetic characters')
        return name

    @validator('breed')
    def validate_breed(cls, breed):
        if not breed.isalpha():
            raise ValueError('Breed should only contain alphabetic characters')
        return breed

    @validator('age')
    def validate_age(cls, age):
        if age < 0:
            raise ValueError('Age cannot be negative')
        return age

def get_dogs(db: Session, owner_id: Optional[str] = None) -> List[Dog]:
    """
    Get a list of dogs from the database.

    Args:
        db (Session): SQLAlchemy database session
        owner_id (str, optional): Filter dogs by owner ID

    Returns:
        List[Dog]: List of Dog objects
    """
    query = db.query(Dog)
    if owner_id:
        query = query.filter(Dog.owner_id == owner_id)
    return query.all()

def create_dog(db: Session, dog_data: DogCreate) -> Dog:
    """
    Create a new dog in the database.

    Args:
        db (Session): SQLAlchemy database session
        dog_data (DogCreate): Pydantic model with dog data

    Returns:
        Dog: The newly created Dog object
    """
    owner = db.query(User).filter(User.id == dog_data.owner_id).first()
    if not owner:
        raise ValueError(f"Owner with ID {dog_data.owner_id} not found")

    dog = Dog(
        name=dog_data.name,
        breed=dog_data.breed,
        age=dog_data.age,
        owner_id=dog_data.owner_id
    )
    db.add(dog)
    db.commit()
    db.refresh(dog)
    return dog

def update_dog(db: Session, dog_id: int, dog_data: DogCreate) -> Dog:
    """
    Update an existing dog in the database.

    Args:
        db (Session): SQLAlchemy database session
        dog_id (int): ID of the dog to update
        dog_data (DogCreate): Pydantic model with updated dog data

    Returns:
        Dog: The updated Dog object
    """
    dog = db.query(Dog).filter(Dog.id == dog_id).first()
    if not dog:
        raise ValueError(f"Dog with ID {dog_id} not found")

    owner = db.query(User).filter(User.id == dog_data.owner_id).first()
    if not owner:
        raise ValueError(f"Owner with ID {dog_data.owner_id} not found")

    dog.name = dog_data.name
    dog.breed = dog_data.breed
    dog.age = dog_data.age
    dog.owner_id = dog_data.owner_id
    db.commit()
    db.refresh(dog)
    return dog

def delete_dog(db: Session, dog_id: int) -> None:
    """
    Delete a dog from the database.

    Args:
        db (Session): SQLAlchemy database session
        dog_id (int): ID of the dog to delete

    Returns:
        None
    """
    dog = db.query(Dog).filter(Dog.id == dog_id).first()
    if not dog:
        raise ValueError(f"Dog with ID {dog_id} not found")

    db.delete(dog)
    db.commit()