feat(promo): Добавлены промокоды на скидку в процентах

db/dal/active_discount_dal.py

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+import logging
+from typing import Optional
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.future import select
+from sqlalchemy import delete
+from datetime import datetime, timezone
+
+from db.models import ActiveDiscount, PromoCode
+
+
+async def set_active_discount(
+    session: AsyncSession,
+    user_id: int,
+    promo_code_id: int,
+    discount_percentage: int
+) -> Optional[ActiveDiscount]:
+    """
+    Set active discount for user.
+    Returns None if user already has an active discount (enforce one-at-a-time rule).
+    """
+    # Check if user already has an active discount
+    existing = await get_active_discount(session, user_id)
+    if existing:
+        logging.warning(
+            f"User {user_id} already has active discount (promo_code_id: {existing.promo_code_id}). "
+            f"Cannot activate new discount {promo_code_id}."
+        )
+        return None
+
+    # Create new active discount
+    new_discount = ActiveDiscount(
+        user_id=user_id,
+        promo_code_id=promo_code_id,
+        discount_percentage=discount_percentage,
+        activated_at=datetime.now(timezone.utc)
+    )
+    session.add(new_discount)
+    await session.flush()
+    await session.refresh(new_discount)
+    logging.info(
+        f"Active discount set for user {user_id}: promo_code_id={promo_code_id}, "
+        f"discount={discount_percentage}%"
+    )
+    return new_discount
+
+
+async def get_active_discount(
+    session: AsyncSession,
+    user_id: int
+) -> Optional[ActiveDiscount]:
+    """Get active discount for user if exists."""
+    stmt = select(ActiveDiscount).where(ActiveDiscount.user_id == user_id)
+    result = await session.execute(stmt)
+    return result.scalar_one_or_none()
+
+
+async def clear_active_discount(
+    session: AsyncSession,
+    user_id: int
+) -> bool:
+    """
+    Clear active discount for user.
+    Returns True if discount was cleared, False if no discount was found.
+    """
+    stmt = delete(ActiveDiscount).where(ActiveDiscount.user_id == user_id)
+    result = await session.execute(stmt)
+    await session.flush()
+    cleared = result.rowcount > 0
+    if cleared:
+        logging.info(f"Active discount cleared for user {user_id}")
+    return cleared