from sqlalchemy import or_, select
from sqlalchemy.exc import IntegrityError

from app.extensions import db

from .models import User


class DuplicateUserError(ValueError):
    pass


def create_user(username: str, email: str, password: str) -> User:
    normalized_username = username.strip()
    normalized_email = email.strip().lower()

    existing_user = db.session.scalar(
        select(User).where(
            or_(
                User.username == normalized_username,
                User.email == normalized_email,
            )
        )
    )
    if existing_user is not None:
        raise DuplicateUserError("That username or email is already registered.")

    user = User(username=normalized_username, email=normalized_email)
    user.set_password(password)
    db.session.add(user)

    try:
        db.session.commit()
    except IntegrityError as exc:
        db.session.rollback()
        raise DuplicateUserError(
            "That username or email is already registered."
        ) from exc

    return user


def authenticate_user(email: str, password: str) -> User | None:
    user = db.session.scalar(
        select(User).where(User.email == email.strip().lower())
    )
    if user is None or not user.check_password(password):
        return None
    return user