import random
import string
from datetime import datetime, timedelta

from sqlalchemy.orm import Session

from app.config import settings
from app.models.user import User
from app.models.verification_token import TokenType, VerificationToken


def _generate_code(length: int = 6) -> str:
    return "".join(random.choices(string.digits, k=length))


def _invalidate_tokens(db: Session, user_id: int, token_type: TokenType) -> None:
    db.query(VerificationToken).filter(
        VerificationToken.user_id == user_id,
        VerificationToken.token_type == token_type,
    ).delete()


def create_verification_token(
    db: Session, user: User, token_type: TokenType
) -> VerificationToken:
    _invalidate_tokens(db, user.id, token_type)

    if token_type == TokenType.activation:
        hours = settings.activation_code_expire_hours
    else:
        hours = settings.password_reset_code_expire_hours

    token = VerificationToken(
        user_id=user.id,
        code=_generate_code(),
        token_type=token_type,
        expires_at=datetime.utcnow() + timedelta(hours=hours),
    )
    db.add(token)
    db.flush()
    return token


def verify_code(
    db: Session, email: str, code: str, token_type: TokenType
) -> User | None:
    from app.auth import get_user_by_email

    user = get_user_by_email(db, email)
    if not user:
        return None

    token = (
        db.query(VerificationToken)
        .filter(
            VerificationToken.user_id == user.id,
            VerificationToken.token_type == token_type,
            VerificationToken.code == code.strip(),
            VerificationToken.expires_at > datetime.utcnow(),
        )
        .first()
    )
    if not token:
        return None

    db.delete(token)
    return user