"""Challenge service for business logic."""
from typing import List, Optional
from sqlalchemy.orm import Session
from sqlalchemy import func
from backend.models.challenge import Challenge
from backend.schemas.challenge import ChallengeCreate


class ChallengeService:
    """Service for challenge operations."""

    @staticmethod
    def create_challenge(
        db: Session,
        challenge_data: ChallengeCreate,
        user_id: int
    ) -> Challenge:
        """Create a new challenge for a user."""
        # Calculate next display_order for THIS user
        max_order = db.query(func.max(Challenge.display_order)).filter(
            Challenge.user_id == user_id
        ).scalar()
        new_order = (max_order if max_order is not None else -1) + 1
        
        db_challenge = Challenge(
            **challenge_data.dict(),
            display_order=new_order,
            user_id=user_id
        )
        db.add(db_challenge)
        db.commit()
        db.refresh(db_challenge)
        return db_challenge

    @staticmethod
    def get_user_challenges(
        db: Session,
        user_id: int
    ) -> List[Challenge]:
        """Get all challenges for a user."""
        challenges = db.query(Challenge).filter(
            Challenge.user_id == user_id
        ).order_by(Challenge.display_order.asc()).all()
        return challenges

    @staticmethod
    def reorder_challenges(
        db: Session,
        ordered_ids: List[int],
        user_id: int
    ) -> None:
        """Reorder challenges for a user."""
        for index, challenge_id in enumerate(ordered_ids):
            db.query(Challenge).filter(
                Challenge.id == challenge_id,
                Challenge.user_id == user_id
            ).update({"display_order": index})
        db.commit()

    @staticmethod
    def delete_challenge(
        db: Session,
        challenge_id: int,
        user_id: int
    ) -> Optional[Challenge]:
        """Delete a challenge for a user."""
        db_challenge = db.query(Challenge).filter(
            Challenge.id == challenge_id,
            Challenge.user_id == user_id
        ).first()
        if db_challenge:
            db.delete(db_challenge)
            db.commit()
        return db_challenge

    @staticmethod
    def get_challenge_by_id(
        db: Session,
        challenge_id: int,
        user_id: int
    ) -> Optional[Challenge]:
        """Get a challenge by ID for a user."""
        return db.query(Challenge).filter(
            Challenge.id == challenge_id,
            Challenge.user_id == user_id
        ).first()