From 51999df5e0beed6c53053c28f286f37dc915d40f Mon Sep 17 00:00:00 2001
From: Emre Akinci <eemreakinci@gmail.com>
Date: Thu, 14 Apr 2022 19:31:08 +0300
Subject: [PATCH 1/3] Add middleware support

---
 src/index.ts                           |  9 ++++++++-
 src/types.ts                           |  6 ++++++
 src/web3-adapter/sendJsonRpcPayload.ts | 18 ++++++++++++++----
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/index.ts b/src/index.ts
index dbbde58..0f875bd 100644
--- 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
index 87cf888..a577912 100644
--- 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
index ae2cb7e..48f70e7 100644
--- 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 +65,14 @@ export function makeJsonRpcPayloadSender(
       }
       return sendJsonRpcWithProvider(currentWriteProvider, payload);
     }
+  });
+
+  const sendJsonRpcPayload = (
+    payload: SingleOrBatchRequest,
+  ): Promise<SingleOrBatchResponse> => {
+    let i = 0;
+    const next = () => middlewares[i++](payload, next);
+    return next();
   };
 
   function setWriteProvider(writeProvider: Provider | null | undefined) {

From 0ba21e32bc13f4afa164d770ab0c090d1c4e02ed Mon Sep 17 00:00:00 2001
From: Emre Akinci <eemreakinci@gmail.com>
Date: Fri, 15 Apr 2022 22:26:51 +0300
Subject: [PATCH 2/3] Handle calling a middleware twice

---
 src/web3-adapter/sendJsonRpcPayload.ts | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/web3-adapter/sendJsonRpcPayload.ts b/src/web3-adapter/sendJsonRpcPayload.ts
index 48f70e7..3e781b0 100644
--- a/src/web3-adapter/sendJsonRpcPayload.ts
+++ b/src/web3-adapter/sendJsonRpcPayload.ts
@@ -71,8 +71,18 @@ export function makeJsonRpcPayloadSender(
     payload: SingleOrBatchRequest,
   ): Promise<SingleOrBatchResponse> => {
     let i = 0;
-    const next = () => middlewares[i++](payload, next);
-    return next();
+    const getNext = () => {
+      let called = false;
+      const middleware = middlewares[i++];
+      return () => {
+        if (called) {
+          throw new Error(`Cannot call "next" in a middleware twice`);
+        }
+        called = true;
+        return middleware(payload, getNext());
+      };
+    };
+    return getNext()();
   };
 
   function setWriteProvider(writeProvider: Provider | null | undefined) {

From 3ee0298ccefe4e3b543e6f5132d132c936358ac9 Mon Sep 17 00:00:00 2001
From: Emre Akinci <eemreakinci@gmail.com>
Date: Mon, 18 Apr 2022 01:00:03 +0300
Subject: [PATCH 3/3] Allow calling `next` multiple times in middleware

---
 src/web3-adapter/sendJsonRpcPayload.ts | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/src/web3-adapter/sendJsonRpcPayload.ts b/src/web3-adapter/sendJsonRpcPayload.ts
index 3e781b0..9adc526 100644
--- a/src/web3-adapter/sendJsonRpcPayload.ts
+++ b/src/web3-adapter/sendJsonRpcPayload.ts
@@ -70,19 +70,11 @@ export function makeJsonRpcPayloadSender(
   const sendJsonRpcPayload = (
     payload: SingleOrBatchRequest,
   ): Promise<SingleOrBatchResponse> => {
-    let i = 0;
-    const getNext = () => {
-      let called = false;
-      const middleware = middlewares[i++];
-      return () => {
-        if (called) {
-          throw new Error(`Cannot call "next" in a middleware twice`);
-        }
-        called = true;
-        return middleware(payload, getNext());
-      };
+    const getNext = (i: number) => {
+      const middleware = middlewares[i];
+      return () => middleware(payload, getNext(i + 1));
     };
-    return getNext()();
+    return getNext(0)();
   };
 
   function setWriteProvider(writeProvider: Provider | null | undefined) {