Merge pull request #122 from emr/middleware-support

Add middleware support
alchemyplatform · Apr 21, 2022 · 75da446 · 75da446
2 parents 51f0417 + 3ee0298
commit 75da446
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Showing 3 changed files with 30 additions and 5 deletions.
diff --git a/src/index.ts b/src/index.ts
@@ -243,11 +243,18 @@ export function createAlchemyWeb3(
 
 function fillInConfigDefaults({
   writeProvider = getWindowProvider(),
+  jsonRpcSenderMiddlewares = [],
   maxRetries = DEFAULT_MAX_RETRIES,
   retryInterval = DEFAULT_RETRY_INTERVAL,
   retryJitter = DEFAULT_RETRY_JITTER,
 }: AlchemyWeb3Config = {}): FullConfig {
-  return { writeProvider, maxRetries, retryInterval, retryJitter };
+  return {
+    writeProvider,
+    jsonRpcSenderMiddlewares,
+    maxRetries,
+    retryInterval,
+    retryJitter,
+  };
 }
 
 function getWindowProvider(): Provider | null {

diff --git a/src/types.ts b/src/types.ts
@@ -53,6 +53,7 @@ export function isSubscriptionEvent(
 
 export interface AlchemyWeb3Config {
   writeProvider?: Provider | null;
+  jsonRpcSenderMiddlewares?: JsonRpcSenderMiddleware[];
   maxRetries?: number;
   retryInterval?: number;
   retryJitter?: number;
@@ -86,3 +87,8 @@ export type SendJsonRpcFunction = (
 export interface TransactionsOptions {
   address?: string;
 }
+
+export type JsonRpcSenderMiddleware = (
+  req: SingleOrBatchRequest,
+  next: () => Promise<SingleOrBatchResponse>,
+) => Promise<SingleOrBatchResponse>;
diff --git a/src/web3-adapter/sendJsonRpcPayload.ts b/src/web3-adapter/sendJsonRpcPayload.ts
@@ -3,6 +3,7 @@ import {
   FullConfig,
   JsonRpcRequest,
   JsonRpcResponse,
+  JsonRpcSenderMiddleware,
   Provider,
   SingleOrBatchRequest,
   SingleOrBatchResponse,
@@ -34,11 +35,12 @@ export function makeJsonRpcPayloadSender(
   alchemySendJsonRpc: AlchemySendJsonRpcFunction,
   config: FullConfig,
 ): JsonRpcPayloadSender {
-  let currentWriteProvider = config.writeProvider;
+  // Copy middlewares from config.
+  const middlewares: JsonRpcSenderMiddleware[] = [];
+  config.jsonRpcSenderMiddlewares.forEach((m) => middlewares.push(m));
 
-  const sendJsonRpcPayload = (
-    payload: SingleOrBatchRequest,
-  ): Promise<SingleOrBatchResponse> => {
+  let currentWriteProvider = config.writeProvider;
+  middlewares.push((payload) => {
     const disallowedMethod = getDisallowedMethod(payload);
     if (!disallowedMethod) {
       try {
@@ -63,6 +65,16 @@ export function makeJsonRpcPayloadSender(
       }
       return sendJsonRpcWithProvider(currentWriteProvider, payload);
     }
+  });
+
+  const sendJsonRpcPayload = (
+    payload: SingleOrBatchRequest,
+  ): Promise<SingleOrBatchResponse> => {
+    const getNext = (i: number) => {
+      const middleware = middlewares[i];
+      return () => middleware(payload, getNext(i + 1));
+    };
+    return getNext(0)();
   };
 
   function setWriteProvider(writeProvider: Provider | null | undefined) {