feat: add generic lnurl error response handler (#2638)

* feat: add generic lnurl error response handler

this is used multiple times in extensions to safeguard `views_lnurl.py`
endpoint to not return a wrong lnurl error response.

you use it by just setting following on your lnurl router/view

```
withdraw_ext_lnurl = APIRouter(prefix="/api/v1/lnurl")
withdraw_ext_lnurl.route_class = LNURLErrorResponseHandler
```

lnbits/core/services.py

@@ -25,6 +25,7 @@ from lnbits.decorators import (
     check_user_extension_access,
     require_admin_key,
 )
+from lnbits.exceptions import InvoiceError, PaymentError
 from lnbits.helpers import url_for
 from lnbits.lnurl import LnurlErrorResponse
 from lnbits.lnurl import decode as decode_lnurl
@@ -70,18 +71,6 @@ from .helpers import to_valid_user_id
 from .models import BalanceDelta, Payment, PaymentState, User, UserConfig, Wallet
 
 
-class PaymentError(Exception):
-    def __init__(self, message: str, status: str = "pending"):
-        self.message = message
-        self.status = status
-
-
-class InvoiceError(Exception):
-    def __init__(self, message: str, status: str = "pending"):
-        self.message = message
-        self.status = status
-
-
 async def calculate_fiat_amounts(
     amount: float,
     wallet_id: str,

lnbits/exceptions.py

@@ -8,11 +8,21 @@ from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse, RedirectResponse, Response
 from loguru import logger
 
-from lnbits.core.services import InvoiceError, PaymentError
-
 from .helpers import template_renderer
 
 
+class PaymentError(Exception):
+    def __init__(self, message: str, status: str = "pending"):
+        self.message = message
+        self.status = status
+
+
+class InvoiceError(Exception):
+    def __init__(self, message: str, status: str = "pending"):
+        self.message = message
+        self.status = status
+
+
 def register_exception_handlers(app: FastAPI):
     register_exception_handler(app)
     register_request_validation_exception_handler(app)

lnbits/lnurl.py

@@ -1 +1,65 @@
-from lnurl import LnurlErrorResponse, decode, encode, handle  # noqa: F401
+from typing import Callable
+
+from fastapi import HTTPException, Request, Response
+from fastapi.responses import JSONResponse
+from fastapi.routing import APIRoute
+from lnurl import LnurlErrorResponse, decode, encode, handle
+from loguru import logger
+
+from lnbits.exceptions import InvoiceError, PaymentError
+
+
+class LnurlErrorResponseHandler(APIRoute):
+    """
+    Custom APIRoute class to handle LNURL errors.
+    LNURL errors always return with status 200 and
+    a JSON response with `status="ERROR"` and a `reason` key.
+    Helps to catch HTTPException and return a valid lnurl error response
+
+    Example:
+    withdraw_lnurl_router = APIRouter(prefix="/api/v1/lnurl")
+    withdraw_lnurl_router.route_class = LnurlErrorResponseHandler
+    """
+
+    def get_route_handler(self) -> Callable:
+        original_route_handler = super().get_route_handler()
+
+        async def lnurl_route_handler(request: Request) -> Response:
+            try:
+                response = await original_route_handler(request)
+                return response
+            except (InvoiceError, PaymentError) as exc:
+                logger.debug(f"Wallet Error: {exc}")
+                response = JSONResponse(
+                    status_code=200,
+                    content={"status": "ERROR", "reason": f"{exc.message}"},
+                )
+                return response
+            except HTTPException as exc:
+                logger.debug(f"HTTPException: {exc}")
+                response = JSONResponse(
+                    status_code=200,
+                    content={"status": "ERROR", "reason": f"{exc.detail}"},
+                )
+                return response
+            except Exception as exc:
+                logger.error("Unknown Error:", exc)
+                response = JSONResponse(
+                    status_code=200,
+                    content={
+                        "status": "ERROR",
+                        "reason": f"UNKNOWN ERROR: {exc!s}",
+                    },
+                )
+                return response
+
+        return lnurl_route_handler
+
+
+__all__ = [
+    "decode",
+    "encode",
+    "handle",
+    "LnurlErrorResponse",
+    "LnurlErrorResponseHandler",
+]