Add interceptors for MITM

packages/safe-chain/src/registryProxy/interceptors/interceptorBuilder.js

@@ -0,0 +1,50 @@
+/**
+ * @typedef {import('./requestInterceptorBuilder.js').RequestInterceptorBuilder} RequestInterceptorBuilder
+ * @typedef {import('./requestInterceptorBuilder.js').RequestInterceptor} RequestInterceptor
+ *
+ * @typedef {Object} InterceptorBuilder
+ * @property {(requestFunc: (requestHandlerBuilder: RequestInterceptorBuilder) => Promise<void>) => void} onRequest
+ * @property {() => Interceptor} build
+ *
+ * @typedef {Object} Interceptor
+ * @property {(targetUrl: string) => Promise<RequestInterceptor>} handleRequest
+ */
+
+import { createRequestInterceptorBuilder } from "./requestInterceptorBuilder.js";
+
+/**
+ * @returns {InterceptorBuilder}
+ */
+export function createInterceptorBuilder() {
+  /**
+   * @type {Array<(requestHandlerBuilder: RequestInterceptorBuilder) => Promise<void>>}
+   */
+  const requestHandlers = [];
+
+  return {
+    onRequest(requestFunc) {
+      requestHandlers.push(requestFunc);
+    },
+    build() {
+      return buildInterceptor(requestHandlers);
+    },
+  };
+}
+
+/**
+ * @param {Array<(requestHandlerBuilder: RequestInterceptorBuilder) => Promise<void>>} requestHandlers
+ * @returns {Interceptor}
+ */
+function buildInterceptor(requestHandlers) {
+  return {
+    async handleRequest(targetUrl) {
+      const reqInterceptorBuilder = createRequestInterceptorBuilder(targetUrl);
+
+      for (const handler of requestHandlers) {
+        await handler(reqInterceptorBuilder);
+      }
+
+      return reqInterceptorBuilder.build();
+    },
+  };
+}

packages/safe-chain/src/registryProxy/interceptors/requestInterceptorBuilder.js

@@ -0,0 +1,30 @@
+/**
+ * @typedef {Object} RequestInterceptorBuilder
+ * @property {string} targetUrl
+ * @property {(statusCode: number, message: string) => void} blockRequest
+ * @property {() => RequestInterceptor} build
+ *
+ * @typedef {Object} RequestInterceptor
+ * @property {{statusCode: number, message: string} | undefined} blockResponse
+ */
+
+/**
+ * @param {string} targetUrl
+ * @returns {RequestInterceptorBuilder}
+ */
+export function createRequestInterceptorBuilder(targetUrl) {
+  /** @type {{statusCode: number, message: string} | undefined}  */
+  let blockResponse = undefined;
+
+  return {
+    targetUrl,
+    blockRequest(statusCode, message) {
+      blockResponse = { statusCode, message };
+    },
+    build() {
+      return {
+        blockResponse,
+      };
+    },
+  };
+}