adds route and helper to submit transaction to the horizon rpc

src/helper/horizon-rpc.ts

@@ -1,5 +1,5 @@
 import BigNumber from "bignumber.js";
-import { AssetType, Horizon } from "stellar-sdk";
+import { AssetType, Horizon, TransactionBuilder } from "stellar-sdk";
 
 export const BASE_RESERVE = 0.5;
 export const BASE_RESERVE_MIN_COUNT = 2;
@@ -229,3 +229,34 @@ export const fetchAccountHistory = async (
     throw new Error(JSON.stringify(error));
   }
 };
+
+export const submitTransaction = async (
+  signedXDR: string,
+  networkUrl: string,
+  networkPassphrase: string
+): Promise<{
+  data: Horizon.HorizonApi.SubmitTransactionResponse | null;
+  error: unknown;
+}> => {
+  const tx = TransactionBuilder.fromXDR(signedXDR, networkPassphrase);
+  const server = new Horizon.Server(networkUrl);
+
+  try {
+    const data = await server.submitTransaction(tx);
+    return {
+      data,
+      error: null,
+    };
+  } catch (e: any) {
+    if (e.response.status === 504) {
+      // in case of 504, keep retrying this tx until submission succeeds or we get a different error
+      // https://developers.stellar.org/api/errors/http-status-codes/horizon-specific/timeout
+      // https://developers.stellar.org/docs/encyclopedia/error-handling
+      return await submitTransaction(signedXDR, networkUrl, networkPassphrase);
+    }
+    return {
+      data: null,
+      error: e,
+    };
+  }
+};

src/route/index.ts

@@ -12,6 +12,7 @@ import {
   isNetwork,
   NetworkNames,
 } from "../helper/validate";
+import { submitTransaction } from "../helper/horizon-rpc";
 
 const API_VERSION = "v1";
 
@@ -279,6 +280,51 @@ export function initApiServer(
         },
       });
 
+      instance.route({
+        method: "POST",
+        url: "/submit-tx",
+        schema: {
+          body: {
+            type: "object",
+            properties: {
+              signed_xdr: { type: "string" },
+              network_url: { type: "string" },
+              network_passphrase: { type: "string" },
+            },
+          },
+          response: {
+            200: {
+              type: "object",
+              properties: {
+                data: { type: "object" },
+              },
+            },
+          },
+        },
+        handler: async (
+          request: FastifyRequest<{
+            Body: {
+              signed_xdr: string;
+              network_url: string;
+              network_passphrase: string;
+            };
+          }>,
+          reply
+        ) => {
+          const { signed_xdr, network_url, network_passphrase } = request.body;
+          const { data, error } = await submitTransaction(
+            signed_xdr,
+            network_url,
+            network_passphrase
+          );
+          if (error) {
+            reply.code(400).send(error);
+          } else {
+            reply.code(200).send(data);
+          }
+        },
+      });
+
       next();
     },
     { prefix: `/api/${API_VERSION}` }