fix(api): replace UUID type with str for Better-Auth nanoid user IDs (#98)

Better-Auth uses nanoid strings for user IDs, not UUIDs. Changed all
user_id parameter/return types in the API layer from UUID to str,
removed the obsolete UUID import where unused, and updated the
_validate_session_token return type accordingly.

Co-authored-by: CartSnitch Engineer Bot <cartnoreply@cartsnitch.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

src/cartsnitch_api/auth/dependencies.py

@@ -5,7 +5,6 @@ Sessions are verified by querying the shared sessions table directly.
 """
 
 from datetime import UTC, datetime
-from uuid import UUID
 
 from fastapi import Cookie, Depends, Header, HTTPException, Request, status
 from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
@@ -27,10 +26,10 @@ SESSION_COOKIE_NAMES = [
 ]
 
 
-async def _validate_session_token(token: str, db: AsyncSession) -> UUID:
+async def _validate_session_token(token: str, db: AsyncSession) -> str:
     """Validate a Better-Auth session token against the sessions table.
 
-    Returns the user_id (as UUID) if the session is valid and not expired.
+    Returns the user_id (as str) if the session is valid and not expired.
     Better-Auth v1.5.6 stores raw tokens in the DB. The session cookie
     is signed: ``rawToken.base64HMACSignature``. Strip the signature
     before querying.
@@ -60,14 +59,14 @@ async def _validate_session_token(token: str, db: AsyncSession) -> UUID:
             detail="Session expired",
         )
 
-    return UUID(str(user_id))
+    return str(user_id)
 
 
 async def get_current_user(
     request: Request,
     credentials: HTTPAuthorizationCredentials | None = Depends(bearer_scheme),
     db: AsyncSession = Depends(get_db),
-) -> UUID:
+) -> str:
     """Extract and validate the session token from cookie or Authorization header.
 
     Checks in order:

src/cartsnitch_api/auth/jwt.py

@@ -2,22 +2,21 @@
 
 from datetime import UTC, datetime, timedelta
 from typing import Any, cast
-from uuid import UUID
 
 from jose import JWTError, jwt
 
 from cartsnitch_api.config import settings
 
 
-def create_access_token(user_id: UUID) -> str:
+def create_access_token(user_id: str) -> str:
     expire = datetime.now(UTC) + timedelta(minutes=settings.jwt_access_token_expire_minutes)
-    payload = {"sub": str(user_id), "exp": expire, "type": "access"}
+    payload = {"sub": user_id, "exp": expire, "type": "access"}
     return cast(str, jwt.encode(payload, settings.jwt_secret_key, algorithm=settings.jwt_algorithm))
 
 
-def create_refresh_token(user_id: UUID) -> str:
+def create_refresh_token(user_id: str) -> str:
     expire = datetime.now(UTC) + timedelta(days=settings.jwt_refresh_token_expire_days)
-    payload = {"sub": str(user_id), "exp": expire, "type": "refresh"}
+    payload = {"sub": user_id, "exp": expire, "type": "refresh"}
     return cast(str, jwt.encode(payload, settings.jwt_secret_key, algorithm=settings.jwt_algorithm))
 
 

src/cartsnitch_api/auth/routes.py

@@ -5,8 +5,6 @@ the Better-Auth service (auth/). This router provides user profile
 endpoints that query our own user data from the shared database.
 """
 
-from uuid import UUID
-
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -23,7 +21,7 @@ router = APIRouter(prefix="/auth", tags=["auth"])
 
 @router.get("/me", response_model=UserResponse)
 async def get_me(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = AuthService(db)
@@ -38,7 +36,7 @@ async def get_me(
 @router.patch("/me", response_model=UserResponse)
 async def update_me(
     body: UpdateUserRequest,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = AuthService(db)
@@ -54,7 +52,7 @@ async def update_me(
 
 @router.delete("/me", status_code=status.HTTP_204_NO_CONTENT)
 async def delete_me(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = AuthService(db)

src/cartsnitch_api/routes/alerts.py

@@ -1,7 +1,5 @@
 """Alert routes: list alerts, manage settings."""
 
-from uuid import UUID
-
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -15,7 +13,7 @@ router = APIRouter(prefix="/alerts", tags=["alerts"])
 
 @router.get("", response_model=list[AlertResponse])
 async def list_alerts(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = AlertService(db)
@@ -24,7 +22,7 @@ async def list_alerts(
 
 @router.get("/settings", response_model=AlertSettingsResponse)
 async def get_alert_settings(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = AlertService(db)
@@ -34,7 +32,7 @@ async def get_alert_settings(
 @router.put("/settings")
 async def update_alert_settings(
     body: AlertSettingsRequest,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     raise HTTPException(

src/cartsnitch_api/routes/coupons.py

@@ -16,7 +16,7 @@ router = APIRouter(prefix="/coupons", tags=["coupons"])
 @router.get("", response_model=list[CouponResponse])
 async def list_coupons(
     store_id: UUID | None = Query(None),
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = CouponService(db)
@@ -25,7 +25,7 @@ async def list_coupons(
 
 @router.get("/relevant", response_model=list[CouponResponse])
 async def relevant_coupons(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = CouponService(db)

src/cartsnitch_api/routes/prices.py

@@ -20,7 +20,7 @@ router = APIRouter(prefix="/prices", tags=["prices"])
 
 @router.get("/trends", response_model=list[PriceTrendResponse])
 async def price_trends(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     category: str | None = Query(None),
     db: AsyncSession = Depends(get_db),
 ):
@@ -30,7 +30,7 @@ async def price_trends(
 
 @router.get("/increases", response_model=list[PriceIncreaseResponse])
 async def price_increases(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = PriceService(db)
@@ -40,7 +40,7 @@ async def price_increases(
 @router.get("/comparison", response_model=list[PriceComparisonResponse])
 async def price_comparison(
     product_ids: Annotated[list[UUID], Query()],
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = PriceService(db)

src/cartsnitch_api/routes/products.py

@@ -15,7 +15,7 @@ router = APIRouter(prefix="/products", tags=["products"])
 
 @router.get("", response_model=list[ProductResponse])
 async def list_products(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     q: str | None = Query(None),
     category: str | None = Query(None),
     page: int = Query(1, ge=1),
@@ -29,7 +29,7 @@ async def list_products(
 @router.get("/{product_id}", response_model=ProductDetailResponse)
 async def get_product(
     product_id: UUID,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = ProductService(db)
@@ -44,7 +44,7 @@ async def get_product(
 @router.get("/{product_id}/prices", response_model=PriceTrendResponse)
 async def get_product_prices(
     product_id: UUID,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = ProductService(db)

src/cartsnitch_api/routes/purchases.py

@@ -15,7 +15,7 @@ router = APIRouter(prefix="/purchases", tags=["purchases"])
 
 @router.get("", response_model=list[PurchaseResponse])
 async def list_purchases(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     store_id: UUID | None = Query(None),
     page: int = Query(1, ge=1),
     page_size: int = Query(20, ge=1, le=100),
@@ -27,7 +27,7 @@ async def list_purchases(
 
 @router.get("/stats", response_model=PurchaseStatsResponse)
 async def purchase_stats(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = PurchaseService(db)
@@ -37,7 +37,7 @@ async def purchase_stats(
 @router.get("/{purchase_id}", response_model=PurchaseDetailResponse)
 async def get_purchase(
     purchase_id: UUID,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = PurchaseService(db)

src/cartsnitch_api/routes/scraping.py

@@ -1,7 +1,5 @@
 """Scraping routes: trigger sync, check status (proxy to ReceiptWitness)."""
 
-from uuid import UUID
-
 from fastapi import APIRouter, Depends, HTTPException, status
 from httpx import HTTPStatusError, RequestError
 
@@ -13,7 +11,7 @@ router = APIRouter(prefix="/scraping", tags=["scraping"])
 
 
 @router.post("/{store_slug}/sync", response_model=SyncTriggerResponse)
-async def trigger_sync(store_slug: str, user_id: UUID = Depends(get_current_user)):
+async def trigger_sync(store_slug: str, user_id: str = Depends(get_current_user)):
     client = ReceiptWitnessClient()
     try:
         result = await client.trigger_sync(str(user_id), store_slug)
@@ -31,7 +29,7 @@ async def trigger_sync(store_slug: str, user_id: UUID = Depends(get_current_user
 
 
 @router.get("/status", response_model=list[SyncStatusResponse])
-async def sync_status(user_id: UUID = Depends(get_current_user)):
+async def sync_status(user_id: str = Depends(get_current_user)):
     client = ReceiptWitnessClient()
     try:
         return await client.get_sync_status(str(user_id))

src/cartsnitch_api/routes/shopping.py

@@ -1,7 +1,5 @@
 """Shopping routes: optimize list, saved lists."""
 
-from uuid import UUID
-
 from fastapi import APIRouter, Depends, HTTPException, status
 from httpx import HTTPStatusError, RequestError
 
@@ -13,7 +11,7 @@ router = APIRouter(prefix="/shopping", tags=["shopping"])
 
 
 @router.post("/optimize", response_model=OptimizeResponse)
-async def optimize_shopping(body: OptimizeRequest, user_id: UUID = Depends(get_current_user)):
+async def optimize_shopping(body: OptimizeRequest, user_id: str = Depends(get_current_user)):
     client = ClipArtistClient()
     try:
         result = await client.optimize(
@@ -37,7 +35,7 @@ async def optimize_shopping(body: OptimizeRequest, user_id: UUID = Depends(get_c
 
 
 @router.get("/lists", response_model=list[ShoppingListResponse])
-async def list_shopping_lists(user_id: UUID = Depends(get_current_user)):
+async def list_shopping_lists(user_id: str = Depends(get_current_user)):
     client = ClipArtistClient()
     try:
         return await client.get_shopping_lists(str(user_id))

src/cartsnitch_api/routes/stores.py

@@ -1,7 +1,5 @@
 """Store routes: list stores, manage user store connections."""
 
-from uuid import UUID
-
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -21,7 +19,7 @@ async def list_stores(db: AsyncSession = Depends(get_db)):
 
 @router.get("/me/stores", response_model=list[StoreAccountResponse])
 async def list_user_stores(
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = StoreService(db)
@@ -36,7 +34,7 @@ async def list_user_stores(
 async def connect_store(
     store_slug: str,
     body: ConnectStoreRequest,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = StoreService(db)
@@ -51,7 +49,7 @@ async def connect_store(
 @router.delete("/me/stores/{store_slug}", status_code=status.HTTP_204_NO_CONTENT)
 async def disconnect_store(
     store_slug: str,
-    user_id: UUID = Depends(get_current_user),
+    user_id: str = Depends(get_current_user),
     db: AsyncSession = Depends(get_db),
 ):
     svc = StoreService(db)

src/cartsnitch_api/services/alerts.py

@@ -4,8 +4,6 @@ Alerts are generated by StickerShock and ShrinkRay services and written to the D
 This service reads them for the API gateway.
 """
 
-from uuid import UUID
-
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
@@ -15,7 +13,7 @@ class AlertService:
     def __init__(self, db: AsyncSession) -> None:
         self.db = db
 
-    async def list_alerts(self, user_id: UUID) -> list[dict]:
+    async def list_alerts(self, user_id: str) -> list[dict]:
         """List shrinkflation events for products the user has purchased."""
         from cartsnitch_api.models import Purchase, PurchaseItem, ShrinkflationEvent
 
@@ -57,7 +55,7 @@ class AlertService:
             for e in events
         ]
 
-    async def get_settings(self, user_id: UUID) -> dict:
+    async def get_settings(self, user_id: str) -> dict:
         # Alert settings would be stored in a user_settings table.
         # For now, return defaults since the table doesn't exist yet in common lib.
         return {
@@ -66,7 +64,7 @@ class AlertService:
             "email_notifications": False,
         }
 
-    async def update_settings(self, user_id: UUID, **fields) -> dict:
+    async def update_settings(self, user_id: str, **fields) -> dict:
         # Would update user_settings table. Return merged defaults for now.
         current = await self.get_settings(user_id)
         for k, v in fields.items():

src/cartsnitch_api/services/auth.py

@@ -5,8 +5,6 @@ handled by the Better-Auth service (auth/). This service provides
 user lookup and profile update operations for the API gateway.
 """
 
-from uuid import UUID
-
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -15,7 +13,7 @@ class AuthService:
     def __init__(self, db: AsyncSession) -> None:
         self.db = db
 
-    async def get_user(self, user_id: UUID) -> dict:
+    async def get_user(self, user_id: str) -> dict:
         from cartsnitch_api.models import User
 
         result = await self.db.execute(select(User).where(User.id == user_id))
@@ -30,7 +28,7 @@ class AuthService:
             "created_at": user.created_at,
         }
 
-    async def update_user(self, user_id: UUID, **fields) -> dict:
+    async def update_user(self, user_id: str, **fields) -> dict:
         from cartsnitch_api.models import User
 
         result = await self.db.execute(select(User).where(User.id == user_id))
@@ -58,7 +56,7 @@ class AuthService:
             "created_at": user.created_at,
         }
 
-    async def delete_user(self, user_id: UUID) -> None:
+    async def delete_user(self, user_id: str) -> None:
         from cartsnitch_api.models import User
 
         result = await self.db.execute(select(User).where(User.id == user_id))

src/cartsnitch_api/services/coupons.py

@@ -29,7 +29,7 @@ class CouponService:
         coupons = result.scalars().all()
         return [self._to_dict(c) for c in coupons]
 
-    async def relevant_coupons(self, user_id: UUID) -> list[dict]:
+    async def relevant_coupons(self, user_id: str) -> list[dict]:
         """Coupons for products the user has purchased."""
         from cartsnitch_api.models import Coupon, PurchaseItem
 

src/cartsnitch_api/services/purchases.py

@@ -13,7 +13,7 @@ class PurchaseService:
 
     async def list_purchases(
         self,
-        user_id: UUID,
+        user_id: str,
         store_id: UUID | None = None,
         page: int = 1,
         page_size: int = 20,
@@ -56,7 +56,7 @@ class PurchaseService:
             for p, item_count, store_name in result.all()
         ]
 
-    async def get_purchase(self, purchase_id: UUID, user_id: UUID) -> dict:
+    async def get_purchase(self, purchase_id: UUID, user_id: str) -> dict:
         from cartsnitch_api.models import Purchase
 
         result = await self.db.execute(
@@ -88,7 +88,7 @@ class PurchaseService:
             ],
         }
 
-    async def get_stats(self, user_id: UUID) -> dict:
+    async def get_stats(self, user_id: str) -> dict:
         from cartsnitch_api.models import Purchase
 
         result = await self.db.execute(

src/cartsnitch_api/services/stores.py

@@ -1,7 +1,6 @@
 """Store service — list stores, manage user store account connections."""
 
 import json
-from uuid import UUID
 
 from cryptography.fernet import Fernet
 from sqlalchemy import select
@@ -35,7 +34,7 @@ class StoreService:
             for s in stores
         ]
 
-    async def list_user_stores(self, user_id: UUID) -> list[dict]:
+    async def list_user_stores(self, user_id: str) -> list[dict]:
         from cartsnitch_api.models import UserStoreAccount
 
         result = await self.db.execute(
@@ -60,7 +59,7 @@ class StoreService:
             for a in accounts
         ]
 
-    async def connect_store(self, user_id: UUID, store_slug: str, credentials: dict | None) -> dict:
+    async def connect_store(self, user_id: str, store_slug: str, credentials: dict | None) -> dict:
         from cartsnitch_api.models import Store, UserStoreAccount
 
         result = await self.db.execute(select(Store).where(Store.slug == store_slug))
@@ -107,7 +106,7 @@ class StoreService:
             "sync_status": "active",
         }
 
-    async def disconnect_store(self, user_id: UUID, store_slug: str) -> None:
+    async def disconnect_store(self, user_id: str, store_slug: str) -> None:
         from cartsnitch_api.models import Store, UserStoreAccount
 
         result = await self.db.execute(select(Store).where(Store.slug == store_slug))