BUG: proper exception for already paid internal invoices (#1593)

* BUG: proper exception for paid interal invoices

* test should now fail, because we pay invoice twice, and should also work in regtest

* sorting

* unpack check_internal

* introduce another crud fn for checking internal paid payment

* rename

---------

Co-authored-by: callebtc <93376500+callebtc@users.noreply.github.com>

lnbits/core/crud.py

@@ -604,6 +604,22 @@ async def check_internal(
         return row["checking_id"]
 
 
+async def check_internal_pending(
+    payment_hash: str, conn: Optional[Connection] = None
+) -> bool:
+    row = await (conn or db).fetchone(
+        """
+        SELECT pending FROM apipayments
+        WHERE hash = ? AND amount > 0
+        """,
+        (payment_hash,),
+    )
+    if not row:
+        return False
+    else:
+        return row["pending"]
+
+
 # balance_check
 # -------------
 

lnbits/core/services.py

@@ -27,6 +27,7 @@ from lnbits.wallets.base import PaymentResponse, PaymentStatus
 from . import db
 from .crud import (
     check_internal,
+    check_internal_pending,
     create_account,
     create_admin_settings,
     create_payment,
@@ -153,6 +154,9 @@ async def pay_invoice(
             extra=extra,
         )
 
+        if not await check_internal_pending(invoice.payment_hash, conn=conn):
+            raise PaymentFailure("Internal invoice already paid.")
+
         # check_internal() returns the checking_id of the invoice we're waiting for
         internal_checking_id = await check_internal(invoice.payment_hash, conn=conn)
         if internal_checking_id: