Add shop

backend/app/services/coins.py

@@ -0,0 +1,288 @@
+"""
+Coins Service - handles all coin-related operations
+
+Coins are earned only in certified marathons and can be spent in the shop.
+"""
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models import User, Participant, Marathon, CoinTransaction, CoinTransactionType
+from app.models.challenge import Difficulty
+
+
+class CoinsService:
+    """Service for managing coin transactions and balances"""
+
+    # Coins awarded per challenge difficulty (only in certified marathons)
+    CHALLENGE_COINS = {
+        Difficulty.EASY.value: 5,
+        Difficulty.MEDIUM.value: 12,
+        Difficulty.HARD.value: 25,
+    }
+
+    # Coins for playthrough = points * this ratio
+    PLAYTHROUGH_COIN_RATIO = 0.05  # 5% of points
+
+    # Coins awarded for marathon placements
+    MARATHON_PLACE_COINS = {
+        1: 100,  # 1st place
+        2: 50,   # 2nd place
+        3: 30,   # 3rd place
+    }
+
+    # Bonus coins for Common Enemy event winners
+    COMMON_ENEMY_BONUS_COINS = {
+        1: 15,  # First to complete
+        2: 10,  # Second
+        3: 5,   # Third
+    }
+
+    async def award_challenge_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+        difficulty: str,
+        assignment_id: int,
+    ) -> int:
+        """
+        Award coins for completing a challenge.
+        Only awards coins if marathon is certified.
+
+        Returns: number of coins awarded (0 if marathon not certified)
+        """
+        if not marathon.is_certified:
+            return 0
+
+        coins = self.CHALLENGE_COINS.get(difficulty, 0)
+        if coins <= 0:
+            return 0
+
+        # Create transaction
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=coins,
+            transaction_type=CoinTransactionType.CHALLENGE_COMPLETE.value,
+            reference_type="assignment",
+            reference_id=assignment_id,
+            description=f"Challenge completion ({difficulty})",
+        )
+        db.add(transaction)
+
+        # Update balances
+        user.coins_balance += coins
+        participant.coins_earned += coins
+
+        return coins
+
+    async def award_playthrough_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+        points: int,
+        assignment_id: int,
+    ) -> int:
+        """
+        Award coins for completing a playthrough.
+        Coins = points * PLAYTHROUGH_COIN_RATIO
+
+        Returns: number of coins awarded (0 if marathon not certified)
+        """
+        if not marathon.is_certified:
+            return 0
+
+        coins = int(points * self.PLAYTHROUGH_COIN_RATIO)
+        if coins <= 0:
+            return 0
+
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=coins,
+            transaction_type=CoinTransactionType.PLAYTHROUGH_COMPLETE.value,
+            reference_type="assignment",
+            reference_id=assignment_id,
+            description=f"Playthrough completion ({points} points)",
+        )
+        db.add(transaction)
+
+        user.coins_balance += coins
+        participant.coins_earned += coins
+
+        return coins
+
+    async def award_marathon_place(
+        self,
+        db: AsyncSession,
+        user: User,
+        marathon: Marathon,
+        place: int,
+    ) -> int:
+        """
+        Award coins for placing in a marathon (1st, 2nd, 3rd).
+
+        Returns: number of coins awarded (0 if not top 3 or not certified)
+        """
+        if not marathon.is_certified:
+            return 0
+
+        coins = self.MARATHON_PLACE_COINS.get(place, 0)
+        if coins <= 0:
+            return 0
+
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=coins,
+            transaction_type=CoinTransactionType.MARATHON_PLACE.value,
+            reference_type="marathon",
+            reference_id=marathon.id,
+            description=f"Marathon #{place} place: {marathon.title}",
+        )
+        db.add(transaction)
+
+        user.coins_balance += coins
+
+        return coins
+
+    async def award_common_enemy_bonus(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+        rank: int,
+        event_id: int,
+    ) -> int:
+        """
+        Award bonus coins for Common Enemy event completion.
+
+        Returns: number of bonus coins awarded
+        """
+        if not marathon.is_certified:
+            return 0
+
+        coins = self.COMMON_ENEMY_BONUS_COINS.get(rank, 0)
+        if coins <= 0:
+            return 0
+
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=coins,
+            transaction_type=CoinTransactionType.COMMON_ENEMY_BONUS.value,
+            reference_type="event",
+            reference_id=event_id,
+            description=f"Common Enemy #{rank} place",
+        )
+        db.add(transaction)
+
+        user.coins_balance += coins
+        participant.coins_earned += coins
+
+        return coins
+
+    async def spend_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        amount: int,
+        description: str,
+        reference_type: str | None = None,
+        reference_id: int | None = None,
+    ) -> bool:
+        """
+        Spend coins (for purchases).
+
+        Returns: True if successful, False if insufficient balance
+        """
+        if user.coins_balance < amount:
+            return False
+
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=-amount,  # Negative for spending
+            transaction_type=CoinTransactionType.PURCHASE.value,
+            reference_type=reference_type,
+            reference_id=reference_id,
+            description=description,
+        )
+        db.add(transaction)
+
+        user.coins_balance -= amount
+        return True
+
+    async def refund_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        amount: int,
+        description: str,
+        reference_type: str | None = None,
+        reference_id: int | None = None,
+    ) -> None:
+        """Refund coins to user (for failed purchases, etc.)"""
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=amount,
+            transaction_type=CoinTransactionType.REFUND.value,
+            reference_type=reference_type,
+            reference_id=reference_id,
+            description=description,
+        )
+        db.add(transaction)
+
+        user.coins_balance += amount
+
+    async def admin_grant_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        amount: int,
+        reason: str,
+        admin_id: int,
+    ) -> None:
+        """Admin grants coins to user"""
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=amount,
+            transaction_type=CoinTransactionType.ADMIN_GRANT.value,
+            reference_type="admin",
+            reference_id=admin_id,
+            description=f"Admin grant: {reason}",
+        )
+        db.add(transaction)
+
+        user.coins_balance += amount
+
+    async def admin_deduct_coins(
+        self,
+        db: AsyncSession,
+        user: User,
+        amount: int,
+        reason: str,
+        admin_id: int,
+    ) -> bool:
+        """
+        Admin deducts coins from user.
+
+        Returns: True if successful, False if insufficient balance
+        """
+        if user.coins_balance < amount:
+            return False
+
+        transaction = CoinTransaction(
+            user_id=user.id,
+            amount=-amount,
+            transaction_type=CoinTransactionType.ADMIN_DEDUCT.value,
+            reference_type="admin",
+            reference_id=admin_id,
+            description=f"Admin deduction: {reason}",
+        )
+        db.add(transaction)
+
+        user.coins_balance -= amount
+        return True
+
+
+# Singleton instance
+coins_service = CoinsService()

backend/app/services/consumables.py

@@ -0,0 +1,323 @@
+"""
+Consumables Service - handles consumable items usage (skip, shield, boost, reroll)
+"""
+from datetime import datetime, timedelta
+from fastapi import HTTPException
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models import (
+    User, Participant, Marathon, Assignment, AssignmentStatus,
+    ShopItem, UserInventory, ConsumableUsage, ConsumableType
+)
+
+
+class ConsumablesService:
+    """Service for consumable items"""
+
+    # Boost settings
+    BOOST_DURATION_HOURS = 2
+    BOOST_MULTIPLIER = 1.5
+
+    async def use_skip(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+        assignment: Assignment,
+    ) -> dict:
+        """
+        Use a Skip to bypass current assignment without penalty.
+
+        - No streak loss
+        - No drop penalty
+        - Assignment marked as dropped but without negative effects
+
+        Returns: dict with result info
+
+        Raises:
+            HTTPException: If skips not allowed or limit reached
+        """
+        # Check marathon settings
+        if not marathon.allow_skips:
+            raise HTTPException(status_code=400, detail="Skips are not allowed in this marathon")
+
+        if marathon.max_skips_per_participant is not None:
+            if participant.skips_used >= marathon.max_skips_per_participant:
+                raise HTTPException(
+                    status_code=400,
+                    detail=f"Skip limit reached ({marathon.max_skips_per_participant} per participant)"
+                )
+
+        # Check assignment is active
+        if assignment.status != AssignmentStatus.ACTIVE.value:
+            raise HTTPException(status_code=400, detail="Can only skip active assignments")
+
+        # Consume skip from inventory
+        item = await self._consume_item(db, user, ConsumableType.SKIP.value)
+
+        # Mark assignment as dropped (but without penalty)
+        assignment.status = AssignmentStatus.DROPPED.value
+        assignment.completed_at = datetime.utcnow()
+        # Note: We do NOT increase drop_count or reset streak
+
+        # Track skip usage
+        participant.skips_used += 1
+
+        # Log usage
+        usage = ConsumableUsage(
+            user_id=user.id,
+            item_id=item.id,
+            marathon_id=marathon.id,
+            assignment_id=assignment.id,
+            effect_data={
+                "type": "skip",
+                "skipped_without_penalty": True,
+            },
+        )
+        db.add(usage)
+
+        return {
+            "success": True,
+            "skipped": True,
+            "penalty": 0,
+            "streak_preserved": True,
+        }
+
+    async def use_shield(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+    ) -> dict:
+        """
+        Activate a Shield - protects from next drop penalty.
+
+        - Next drop will not cause point penalty
+        - Streak is preserved on next drop
+
+        Returns: dict with result info
+
+        Raises:
+            HTTPException: If consumables not allowed or shield already active
+        """
+        if not marathon.allow_consumables:
+            raise HTTPException(status_code=400, detail="Consumables are not allowed in this marathon")
+
+        if participant.has_shield:
+            raise HTTPException(status_code=400, detail="Shield is already active")
+
+        # Consume shield from inventory
+        item = await self._consume_item(db, user, ConsumableType.SHIELD.value)
+
+        # Activate shield
+        participant.has_shield = True
+
+        # Log usage
+        usage = ConsumableUsage(
+            user_id=user.id,
+            item_id=item.id,
+            marathon_id=marathon.id,
+            effect_data={
+                "type": "shield",
+                "activated": True,
+            },
+        )
+        db.add(usage)
+
+        return {
+            "success": True,
+            "shield_activated": True,
+        }
+
+    async def use_boost(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+    ) -> dict:
+        """
+        Activate a Boost - multiplies points for next 2 hours.
+
+        - Points for completed challenges are multiplied by BOOST_MULTIPLIER
+        - Duration: BOOST_DURATION_HOURS
+
+        Returns: dict with result info
+
+        Raises:
+            HTTPException: If consumables not allowed or boost already active
+        """
+        if not marathon.allow_consumables:
+            raise HTTPException(status_code=400, detail="Consumables are not allowed in this marathon")
+
+        if participant.has_active_boost:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Boost already active until {participant.active_boost_expires_at}"
+            )
+
+        # Consume boost from inventory
+        item = await self._consume_item(db, user, ConsumableType.BOOST.value)
+
+        # Activate boost
+        participant.active_boost_multiplier = self.BOOST_MULTIPLIER
+        participant.active_boost_expires_at = datetime.utcnow() + timedelta(hours=self.BOOST_DURATION_HOURS)
+
+        # Log usage
+        usage = ConsumableUsage(
+            user_id=user.id,
+            item_id=item.id,
+            marathon_id=marathon.id,
+            effect_data={
+                "type": "boost",
+                "multiplier": self.BOOST_MULTIPLIER,
+                "duration_hours": self.BOOST_DURATION_HOURS,
+                "expires_at": participant.active_boost_expires_at.isoformat(),
+            },
+        )
+        db.add(usage)
+
+        return {
+            "success": True,
+            "boost_activated": True,
+            "multiplier": self.BOOST_MULTIPLIER,
+            "expires_at": participant.active_boost_expires_at,
+        }
+
+    async def use_reroll(
+        self,
+        db: AsyncSession,
+        user: User,
+        participant: Participant,
+        marathon: Marathon,
+        assignment: Assignment,
+    ) -> dict:
+        """
+        Use a Reroll - discard current assignment and spin again.
+
+        - Current assignment is cancelled (not dropped)
+        - User can spin the wheel again
+        - No penalty
+
+        Returns: dict with result info
+
+        Raises:
+            HTTPException: If consumables not allowed or assignment not active
+        """
+        if not marathon.allow_consumables:
+            raise HTTPException(status_code=400, detail="Consumables are not allowed in this marathon")
+
+        if assignment.status != AssignmentStatus.ACTIVE.value:
+            raise HTTPException(status_code=400, detail="Can only reroll active assignments")
+
+        # Consume reroll from inventory
+        item = await self._consume_item(db, user, ConsumableType.REROLL.value)
+
+        # Cancel current assignment
+        old_challenge_id = assignment.challenge_id
+        old_game_id = assignment.game_id
+        assignment.status = AssignmentStatus.DROPPED.value
+        assignment.completed_at = datetime.utcnow()
+        # Note: We do NOT increase drop_count (this is a reroll, not a real drop)
+
+        # Log usage
+        usage = ConsumableUsage(
+            user_id=user.id,
+            item_id=item.id,
+            marathon_id=marathon.id,
+            assignment_id=assignment.id,
+            effect_data={
+                "type": "reroll",
+                "rerolled_from_challenge_id": old_challenge_id,
+                "rerolled_from_game_id": old_game_id,
+            },
+        )
+        db.add(usage)
+
+        return {
+            "success": True,
+            "rerolled": True,
+            "can_spin_again": True,
+        }
+
+    async def _consume_item(
+        self,
+        db: AsyncSession,
+        user: User,
+        item_code: str,
+    ) -> ShopItem:
+        """
+        Consume 1 unit of a consumable from user's inventory.
+
+        Returns: The consumed ShopItem
+
+        Raises:
+            HTTPException: If user doesn't have the item
+        """
+        result = await db.execute(
+            select(UserInventory)
+            .options(selectinload(UserInventory.item))
+            .join(ShopItem)
+            .where(
+                UserInventory.user_id == user.id,
+                ShopItem.code == item_code,
+                UserInventory.quantity > 0,
+            )
+        )
+        inv_item = result.scalar_one_or_none()
+
+        if not inv_item:
+            raise HTTPException(
+                status_code=400,
+                detail=f"You don't have any {item_code} in your inventory"
+            )
+
+        # Decrease quantity
+        inv_item.quantity -= 1
+
+        return inv_item.item
+
+    async def get_consumable_count(
+        self,
+        db: AsyncSession,
+        user_id: int,
+        item_code: str,
+    ) -> int:
+        """Get how many of a consumable user has"""
+        result = await db.execute(
+            select(UserInventory.quantity)
+            .join(ShopItem)
+            .where(
+                UserInventory.user_id == user_id,
+                ShopItem.code == item_code,
+            )
+        )
+        quantity = result.scalar_one_or_none()
+        return quantity or 0
+
+    def consume_shield_on_drop(self, participant: Participant) -> bool:
+        """
+        Consume shield when dropping (called from wheel.py).
+
+        Returns: True if shield was consumed, False otherwise
+        """
+        if participant.has_shield:
+            participant.has_shield = False
+            return True
+        return False
+
+    def get_active_boost_multiplier(self, participant: Participant) -> float:
+        """
+        Get current boost multiplier for participant.
+
+        Returns: Multiplier value (1.0 if no active boost)
+        """
+        return participant.get_boost_multiplier()
+
+
+# Singleton instance
+consumables_service = ConsumablesService()

backend/app/services/shop.py

@@ -0,0 +1,297 @@
+"""
+Shop Service - handles shop items, purchases, and inventory management
+"""
+from datetime import datetime
+from fastapi import HTTPException
+from sqlalchemy import select, update
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models import User, ShopItem, UserInventory, ShopItemType
+from app.services.coins import coins_service
+
+
+class ShopService:
+    """Service for shop operations"""
+
+    async def get_available_items(
+        self,
+        db: AsyncSession,
+        item_type: str | None = None,
+        include_unavailable: bool = False,
+    ) -> list[ShopItem]:
+        """
+        Get list of shop items.
+
+        Args:
+            item_type: Filter by item type (frame, title, etc.)
+            include_unavailable: Include inactive/out of stock items
+        """
+        query = select(ShopItem)
+
+        if item_type:
+            query = query.where(ShopItem.item_type == item_type)
+
+        if not include_unavailable:
+            now = datetime.utcnow()
+            query = query.where(
+                ShopItem.is_active == True,
+                (ShopItem.available_from.is_(None)) | (ShopItem.available_from <= now),
+                (ShopItem.available_until.is_(None)) | (ShopItem.available_until >= now),
+                (ShopItem.stock_remaining.is_(None)) | (ShopItem.stock_remaining > 0),
+            )
+
+        query = query.order_by(ShopItem.price.asc())
+        result = await db.execute(query)
+        return list(result.scalars().all())
+
+    async def get_item_by_id(self, db: AsyncSession, item_id: int) -> ShopItem | None:
+        """Get shop item by ID"""
+        result = await db.execute(select(ShopItem).where(ShopItem.id == item_id))
+        return result.scalar_one_or_none()
+
+    async def get_item_by_code(self, db: AsyncSession, code: str) -> ShopItem | None:
+        """Get shop item by code"""
+        result = await db.execute(select(ShopItem).where(ShopItem.code == code))
+        return result.scalar_one_or_none()
+
+    async def purchase_item(
+        self,
+        db: AsyncSession,
+        user: User,
+        item_id: int,
+        quantity: int = 1,
+    ) -> tuple[UserInventory, int]:
+        """
+        Purchase an item from the shop.
+
+        Args:
+            user: The purchasing user
+            item_id: ID of item to purchase
+            quantity: Number to purchase (only for consumables)
+
+        Returns:
+            Tuple of (inventory item, total cost)
+
+        Raises:
+            HTTPException: If item not found, not available, or insufficient funds
+        """
+        # Get item
+        item = await self.get_item_by_id(db, item_id)
+        if not item:
+            raise HTTPException(status_code=404, detail="Item not found")
+
+        # Check availability
+        if not item.is_available:
+            raise HTTPException(status_code=400, detail="Item is not available")
+
+        # For non-consumables, quantity is always 1
+        if item.item_type != ShopItemType.CONSUMABLE.value:
+            quantity = 1
+
+            # Check if already owned
+            existing = await db.execute(
+                select(UserInventory).where(
+                    UserInventory.user_id == user.id,
+                    UserInventory.item_id == item.id,
+                )
+            )
+            if existing.scalar_one_or_none():
+                raise HTTPException(status_code=400, detail="You already own this item")
+
+        # Check stock
+        if item.stock_remaining is not None and item.stock_remaining < quantity:
+            raise HTTPException(status_code=400, detail="Not enough stock available")
+
+        # Calculate total cost
+        total_cost = item.price * quantity
+
+        # Check balance
+        if user.coins_balance < total_cost:
+            raise HTTPException(status_code=400, detail="Not enough coins")
+
+        # Deduct coins
+        success = await coins_service.spend_coins(
+            db, user, total_cost,
+            f"Purchase: {item.name} x{quantity}",
+            "shop_item", item.id,
+        )
+        if not success:
+            raise HTTPException(status_code=400, detail="Payment failed")
+
+        # Add to inventory
+        if item.item_type == ShopItemType.CONSUMABLE.value:
+            # For consumables, increase quantity if already exists
+            existing_result = await db.execute(
+                select(UserInventory).where(
+                    UserInventory.user_id == user.id,
+                    UserInventory.item_id == item.id,
+                )
+            )
+            inv_item = existing_result.scalar_one_or_none()
+
+            if inv_item:
+                inv_item.quantity += quantity
+            else:
+                inv_item = UserInventory(
+                    user_id=user.id,
+                    item_id=item.id,
+                    quantity=quantity,
+                )
+                db.add(inv_item)
+        else:
+            # For cosmetics, create new inventory entry
+            inv_item = UserInventory(
+                user_id=user.id,
+                item_id=item.id,
+                quantity=1,
+            )
+            db.add(inv_item)
+
+        # Decrease stock if limited
+        if item.stock_remaining is not None:
+            item.stock_remaining -= quantity
+
+        await db.flush()
+        return inv_item, total_cost
+
+    async def get_user_inventory(
+        self,
+        db: AsyncSession,
+        user_id: int,
+        item_type: str | None = None,
+    ) -> list[UserInventory]:
+        """Get user's inventory"""
+        query = (
+            select(UserInventory)
+            .options(selectinload(UserInventory.item))
+            .where(UserInventory.user_id == user_id)
+        )
+
+        if item_type:
+            query = query.join(ShopItem).where(ShopItem.item_type == item_type)
+
+        # Exclude empty consumables
+        query = query.where(UserInventory.quantity > 0)
+
+        result = await db.execute(query)
+        return list(result.scalars().all())
+
+    async def get_inventory_item(
+        self,
+        db: AsyncSession,
+        user_id: int,
+        inventory_id: int,
+    ) -> UserInventory | None:
+        """Get specific inventory item"""
+        result = await db.execute(
+            select(UserInventory)
+            .options(selectinload(UserInventory.item))
+            .where(
+                UserInventory.id == inventory_id,
+                UserInventory.user_id == user_id,
+            )
+        )
+        return result.scalar_one_or_none()
+
+    async def equip_item(
+        self,
+        db: AsyncSession,
+        user: User,
+        inventory_id: int,
+    ) -> ShopItem:
+        """
+        Equip a cosmetic item from inventory.
+
+        Returns: The equipped item
+
+        Raises:
+            HTTPException: If item not found or is a consumable
+        """
+        # Get inventory item
+        inv_item = await self.get_inventory_item(db, user.id, inventory_id)
+        if not inv_item:
+            raise HTTPException(status_code=404, detail="Item not found in inventory")
+
+        item = inv_item.item
+
+        if item.item_type == ShopItemType.CONSUMABLE.value:
+            raise HTTPException(status_code=400, detail="Cannot equip consumables")
+
+        # Unequip current item of same type
+        await db.execute(
+            update(UserInventory)
+            .where(
+                UserInventory.user_id == user.id,
+                UserInventory.equipped == True,
+                UserInventory.item_id.in_(
+                    select(ShopItem.id).where(ShopItem.item_type == item.item_type)
+                ),
+            )
+            .values(equipped=False)
+        )
+
+        # Equip new item
+        inv_item.equipped = True
+
+        # Update user's equipped_*_id
+        if item.item_type == ShopItemType.FRAME.value:
+            user.equipped_frame_id = item.id
+        elif item.item_type == ShopItemType.TITLE.value:
+            user.equipped_title_id = item.id
+        elif item.item_type == ShopItemType.NAME_COLOR.value:
+            user.equipped_name_color_id = item.id
+        elif item.item_type == ShopItemType.BACKGROUND.value:
+            user.equipped_background_id = item.id
+
+        return item
+
+    async def unequip_item(
+        self,
+        db: AsyncSession,
+        user: User,
+        item_type: str,
+    ) -> None:
+        """Unequip item of specified type"""
+        # Unequip from inventory
+        await db.execute(
+            update(UserInventory)
+            .where(
+                UserInventory.user_id == user.id,
+                UserInventory.equipped == True,
+                UserInventory.item_id.in_(
+                    select(ShopItem.id).where(ShopItem.item_type == item_type)
+                ),
+            )
+            .values(equipped=False)
+        )
+
+        # Clear user's equipped_*_id
+        if item_type == ShopItemType.FRAME.value:
+            user.equipped_frame_id = None
+        elif item_type == ShopItemType.TITLE.value:
+            user.equipped_title_id = None
+        elif item_type == ShopItemType.NAME_COLOR.value:
+            user.equipped_name_color_id = None
+        elif item_type == ShopItemType.BACKGROUND.value:
+            user.equipped_background_id = None
+
+    async def check_user_owns_item(
+        self,
+        db: AsyncSession,
+        user_id: int,
+        item_id: int,
+    ) -> bool:
+        """Check if user owns an item"""
+        result = await db.execute(
+            select(UserInventory).where(
+                UserInventory.user_id == user_id,
+                UserInventory.item_id == item_id,
+                UserInventory.quantity > 0,
+            )
+        )
+        return result.scalar_one_or_none() is not None
+
+
+# Singleton instance
+shop_service = ShopService()