from typing import List, Dict, Optional, Union
import re
from datetime import datetime
from sqlalchemy.orm import Session
from models.user import User
from schemas.user import UserCreate, UserUpdate

def validate_email(email: str) -> bool:
    """
    Validate an email address format.

    Args:
        email: The email address to validate

    Returns:
        bool: True if email format is valid, False otherwise
    """
    pattern = r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$'
    return bool(re.match(pattern, email))

def get_user_by_email(db: Session, email: str) -> Optional[User]:
    """
    Get a user by their email address.

    Args:
        db: Database session
        email: Email to search for

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

def create_user_safely(db: Session, user_data: UserCreate) -> Union[User, Dict[str, str]]:
    """
    Create a new user with validation and error handling.

    Args:
        db: Database session
        user_data: User data for creation

    Returns:
        User object if created successfully, error dict otherwise
    """
    # Check if email is valid
    if not validate_email(user_data.email):
        return {"error": "Invalid email format"}

    # Check if user already exists
    existing_user = get_user_by_email(db, user_data.email)
    if existing_user:
        return {"error": "Email already registered"}

    # Create the user
    db_user = User(
        username=user_data.username,
        email=user_data.email,
        password=user_data.password  # In a real app, hash this password
    )

    db.add(db_user)
    db.commit()
    db.refresh(db_user)

    return db_user

def update_user(db: Session, user_id: int, user_data: UserUpdate) -> Union[User, Dict[str, str]]:
    """
    Update an existing user's information.

    Args:
        db: Database session
        user_id: ID of the user to update
        user_data: Updated user data

    Returns:
        User object if updated successfully, error dict otherwise
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        return {"error": "User not found"}

    # Update user fields
    if user_data.username:
        user.username = user_data.username
    if user_data.email:
        # Validate email format
        if not validate_email(user_data.email):
            return {"error": "Invalid email format"}
        # Check for duplicate email
        existing_user = get_user_by_email(db, user_data.email)
        if existing_user and existing_user.id != user_id:
            return {"error": "Email already registered"}
        user.email = user_data.email
    if user_data.password:
        user.password = user_data.password  # In a real app, hash this password

    db.commit()
    db.refresh(user)

    return user

def get_user_age(user: User) -> int:
    """
    Calculate the age of a user based on their date of birth.

    Args:
        user: User object

    Returns:
        int: Age of the user
    """
    if not user.date_of_birth:
        return 0

    today = datetime.utcnow().date()
    age = today.year - user.date_of_birth.year
    if today.month < user.date_of_birth.month or (
        today.month == user.date_of_birth.month and today.day < user.date_of_birth.day
    ):
        age -= 1

    return age