# app/modules/loyalty/tasks/point_expiration.py
"""
Point expiration task.

Handles expiring points that are older than the configured
expiration period based on card inactivity.

Runs daily at 02:00 via the scheduled task configuration in definition.py.
"""

import logging
from datetime import UTC, datetime, timedelta

from celery import shared_task
from sqlalchemy.orm import Session

from app.core.database import SessionLocal
from app.modules.loyalty.models import LoyaltyCard, LoyaltyProgram, LoyaltyTransaction
from app.modules.loyalty.models.loyalty_transaction import TransactionType

logger = logging.getLogger(__name__)


@shared_task(name="loyalty.expire_points")
def expire_points() -> dict:
    """
    Expire points that are past their expiration date based on card inactivity.

    For each program with points_expiration_days configured:
    1. Find cards that haven't had activity in the expiration period
    2. Expire all points on those cards
    3. Create POINTS_EXPIRED transaction records
    4. Update card balances

    Returns:
        Summary of expired points
    """
    logger.info("Starting point expiration task...")

    db: Session = SessionLocal()
    try:
        result = _process_point_expiration(db)
        db.commit()
        logger.info(
            f"Point expiration complete: {result['cards_processed']} cards, "
            f"{result['points_expired']} points expired"
        )
        return result
    except Exception as e:
        db.rollback()
        logger.error(f"Point expiration task failed: {e}", exc_info=True)
        return {
            "status": "error",
            "error": str(e),
            "cards_processed": 0,
            "points_expired": 0,
        }
    finally:
        db.close()


def _process_point_expiration(db: Session) -> dict:
    """
    Process point expiration for all programs.

    Args:
        db: Database session

    Returns:
        Summary of expired points
    """
    total_cards_processed = 0
    total_points_expired = 0
    programs_processed = 0

    # Find all active programs with point expiration configured
    programs = (
        db.query(LoyaltyProgram)
        .filter(
            LoyaltyProgram.is_active == True,
            LoyaltyProgram.points_expiration_days.isnot(None),
            LoyaltyProgram.points_expiration_days > 0,
        )
        .all()
    )

    logger.info(f"Found {len(programs)} programs with point expiration configured")

    for program in programs:
        cards_count, points_count = _expire_points_for_program(db, program)
        total_cards_processed += cards_count
        total_points_expired += points_count
        programs_processed += 1

        logger.debug(
            f"Program {program.id} (merchant {program.merchant_id}): "
            f"{cards_count} cards, {points_count} points expired"
        )

    return {
        "status": "success",
        "programs_processed": programs_processed,
        "cards_processed": total_cards_processed,
        "points_expired": total_points_expired,
    }


def _expire_points_for_program(db: Session, program: LoyaltyProgram) -> tuple[int, int]:
    """
    Expire points for a specific loyalty program.

    Args:
        db: Database session
        program: Loyalty program to process

    Returns:
        Tuple of (cards_processed, points_expired)
    """
    if not program.points_expiration_days:
        return 0, 0

    # Calculate expiration threshold
    expiration_threshold = datetime.now(UTC) - timedelta(days=program.points_expiration_days)

    logger.debug(
        f"Processing program {program.id}: expiration after {program.points_expiration_days} days "
        f"(threshold: {expiration_threshold})"
    )

    # Find cards with:
    # - Points balance > 0
    # - Last activity before expiration threshold
    # - Belonging to this program's merchant
    cards_to_expire = (
        db.query(LoyaltyCard)
        .filter(
            LoyaltyCard.merchant_id == program.merchant_id,
            LoyaltyCard.points_balance > 0,
            LoyaltyCard.last_activity_at < expiration_threshold,
            LoyaltyCard.is_active == True,
        )
        .all()
    )

    if not cards_to_expire:
        logger.debug(f"No cards to expire for program {program.id}")
        return 0, 0

    logger.info(f"Found {len(cards_to_expire)} cards to expire for program {program.id}")

    cards_processed = 0
    points_expired = 0

    for card in cards_to_expire:
        if card.points_balance <= 0:
            continue

        expired_points = card.points_balance

        # Create expiration transaction
        transaction = LoyaltyTransaction(
            card_id=card.id,
            merchant_id=program.merchant_id,
            store_id=None,  # System action, no store
            transaction_type=TransactionType.POINTS_EXPIRED.value,
            points_delta=-expired_points,
            points_balance_after=0,
            stamps_delta=0,
            stamps_balance_after=card.stamp_count,
            notes=f"Points expired after {program.points_expiration_days} days of inactivity",
            transaction_at=datetime.now(UTC),
        )
        db.add(transaction)  # noqa: PERF006

        # Update card balance and voided tracking
        card.expire_points(expired_points)
        # Note: We don't update last_activity_at for expiration

        cards_processed += 1
        points_expired += expired_points

        logger.debug(
            f"Expired {expired_points} points from card {card.id} "
            f"(last activity: {card.last_activity_at})"
        )

    return cards_processed, points_expired


# Allow running directly for testing
if __name__ == "__main__":
    import sys

    logging.basicConfig(level=logging.DEBUG)
    result = expire_points()
    print(f"Result: {result}")
    sys.exit(0 if result["status"] == "success" else 1)