feat(marketplace): purchase service with atomic escrow, 30/70 fee splitting and refunds

backend/app/services/wallet.py

@@ -78,6 +78,7 @@ class WalletService:
         reference_id: str | None = None,
         idempotency_key: str | None = None,
         metadata: dict[str, Any] | None = None,
+        commit: bool = True,
     ) -> tuple[Wallet, Transaction]:
         """Credit a user's wallet atomically with row locking.
 
@@ -113,9 +114,12 @@ class WalletService:
             metadata_json=metadata,
         )
         db.add(tx)
-        await db.commit()
-        await db.refresh(wallet)
-        await db.refresh(tx)
+        if commit:
+            await db.commit()
+            await db.refresh(wallet)
+            await db.refresh(tx)
+        else:
+            await db.flush()
         return wallet, tx
 
     @classmethod
@@ -129,6 +133,7 @@ class WalletService:
         reference_id: str | None = None,
         idempotency_key: str | None = None,
         metadata: dict[str, Any] | None = None,
+        commit: bool = True,
     ) -> tuple[Wallet, Transaction]:
         """Debit a user's wallet atomically with row locking and balance check.
 
@@ -154,7 +159,8 @@ class WalletService:
         wallet = await cls.get_or_create_wallet(db, user_id, for_update=True)
         cur_balance = wallet.balance
         if cur_balance < amount:
-            await db.rollback()
+            if commit:
+                await db.rollback()
             raise InsufficientFundsError(
                 f"Insufficient funds: available {cur_balance}, required {amount}"
             )
@@ -172,9 +178,12 @@ class WalletService:
             metadata_json=metadata,
         )
         db.add(tx)
-        await db.commit()
-        await db.refresh(wallet)
-        await db.refresh(tx)
+        if commit:
+            await db.commit()
+            await db.refresh(wallet)
+            await db.refresh(tx)
+        else:
+            await db.flush()
         return wallet, tx
 
     @staticmethod