From 72ac35405c94084164c697f54e990c547393722d Mon Sep 17 00:00:00 2001
From: lollerfirst <43107113+lollerfirst@users.noreply.github.com>
Date: Thu, 6 Mar 2025 00:05:13 +0100
Subject: [PATCH] [NUT-15] LND: Try Multiple Routes (#692)

* try multiple routes

* fix

* Lnd gRPC
---
 cashu/lightning/lnd_grpc/lnd_grpc.py | 33 ++++++++++++++-----------
 cashu/lightning/lndrest.py           | 37 +++++++++++++++++-----------
 2 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/cashu/lightning/lnd_grpc/lnd_grpc.py b/cashu/lightning/lnd_grpc/lnd_grpc.py
index b961c56..2a3af2e 100644
--- a/cashu/lightning/lnd_grpc/lnd_grpc.py
+++ b/cashu/lightning/lnd_grpc/lnd_grpc.py
@@ -245,21 +245,26 @@ class LndRPCWallet(LightningBackend):
                 )
                 """
                 # modify the mpp_record in the last hop
-                route_nr = 0
-                r.routes[route_nr].hops[-1].mpp_record.payment_addr = bytes.fromhex(  # type: ignore
-                    payer_addr
-                )
-                r.routes[route_nr].hops[  # type: ignore
-                    -1
-                ].mpp_record.total_amt_msat = total_amount_msat
-
-                # Send to route request
-                r = await router_stub.SendToRouteV2(
-                    routerrpc.SendToRouteRequest(
-                        payment_hash=bytes.fromhex(invoice.payment_hash),
-                        route=r.routes[route_nr],  # type: ignore
+                for route_nr in range(len(r.routes)):
+                    r.routes[route_nr].hops[-1].mpp_record.payment_addr = bytes.fromhex(  # type: ignore
+                        payer_addr
                     )
-                )
+                    r.routes[route_nr].hops[  # type: ignore
+                        -1
+                    ].mpp_record.total_amt_msat = total_amount_msat
+
+                    # Send to route request
+                    r = await router_stub.SendToRouteV2(
+                        routerrpc.SendToRouteRequest(
+                            payment_hash=bytes.fromhex(invoice.payment_hash),
+                            route=r.routes[route_nr],  # type: ignore
+                        )
+                    )
+                    if r.status == lnrpc.HTLCAttempt.HTLCStatus.FAILED:
+                        if r.failure.code == lnrpc.Failure.FailureCode.TEMPORARY_CHANNEL_FAILURE:
+                            # Try a different route
+                            continue
+                    break
         except AioRpcError as e:
             logger.error(f"QueryRoute or SendToRouteV2 failed: {e}")
             return PaymentResponse(
diff --git a/cashu/lightning/lndrest.py b/cashu/lightning/lndrest.py
index 1baa556..2579590 100644
--- a/cashu/lightning/lndrest.py
+++ b/cashu/lightning/lndrest.py
@@ -259,22 +259,31 @@ class LndRestWallet(LightningBackend):
         }
 
         # add the mpp_record to the last hop
-        rout_nr = 0
-        data["routes"][rout_nr]["hops"][-1].update(mpp_record)
+        r = None    # type: ignore
+        for route_nr in range(len(data["routes"])):
+            logger.debug(f"Trying to pay partial amount with route number {route_nr+1}")
+            data["routes"][route_nr]["hops"][-1].update(mpp_record)
 
-        # send to route
-        r = await self.client.post(
-            url="/v2/router/route/send",
-            json={
-                "payment_hash": base64.b64encode(
-                    bytes.fromhex(invoice.payment_hash)
-                ).decode(),
-                "route": data["routes"][rout_nr],
-            },
-            timeout=None,
-        )
+            # send to route
+            r = await self.client.post(
+                url="/v2/router/route/send",
+                json={
+                    "payment_hash": base64.b64encode(
+                        bytes.fromhex(invoice.payment_hash)
+                    ).decode(),
+                    "route": data["routes"][route_nr],
+                },
+                timeout=None,
+            )
+
+            data = r.json()
+            failure = data.get("failure")
+            if failure:
+                if failure["code"] == 15:
+                    # Try with a different route
+                    continue
+            break
 
-        data = r.json()
         if r.is_error or data.get("message"):
             error_message = data.get("message") or r.text
             return PaymentResponse(