using-deno

- proxy middleware added (for servers)
- readme upd

README.md

@@ -141,6 +141,31 @@ const myFetch = configureFetch(
 );
 ```
 
+### `proxy`
+
+Returns simple proxy middleware. Useful for servers based on Fetch API.
+
+```ts
+import { applyMiddleware } from '@krutoo/fetch-tools';
+import { proxy } from '@krutoo/fetch-tools/middleware';
+
+const enhance = applyMiddleware(
+  proxy({
+    // pathname(s) of incoming request URL which will be proxied
+    filter: ['/api/v2/', '/api/v3/'],
+
+    // define target URL
+    target: 'https://www.my-site.com/',
+  }),
+);
+
+Deno.serve(
+  enhance(req => {
+    return new Response('<h1>Main page</h1>');
+  }),
+);
+```
+
 ## Server utilities
 
 You can use utils for simply configure your HTTP server.

src/middleware/mod.ts

@@ -9,3 +9,4 @@ export {
 } from './log.ts';
 export { retry } from './retry.ts';
 export { validateStatus, type ValidateStatusOptions } from './validate-status.ts';
+export { proxy, type ProxyOptions, type ProxyRequestFilter } from './proxy.ts';

src/middleware/proxy.ts

@@ -0,0 +1,68 @@
+import type { Middleware } from '../types.ts';
+
+export interface ProxyRequestFilter {
+  (url: URL, request: Request): boolean;
+}
+
+export interface ProxyOptions {
+  filter: string | string[] | ProxyRequestFilter;
+  target: string;
+}
+
+/**
+ * Simple proxy middleware for servers based on Web Fetch API.
+ * Based on good article: https://blog.r0b.io/post/creating-a-proxy-with-deno/
+ */
+export function proxy({ filter, target }: ProxyOptions): Middleware {
+  const matches = createMatches(filter);
+
+  const createRequest = (url: URL, request: Request) => {
+    const targetURL = new URL(`.${url.pathname}`, target);
+    targetURL.search = url.search;
+
+    const headers = new Headers(request.headers);
+    headers.set('Host', targetURL.hostname);
+
+    return new Request(targetURL, {
+      method: request.method,
+      headers,
+      body: request.body,
+      redirect: 'manual',
+    });
+  };
+
+  return (request, next) => {
+    const url = new URL(request.url);
+
+    if (!matches(url, request)) {
+      return next(request);
+    }
+
+    console.log('go proxy!');
+
+    return fetch(createRequest(url, request)).then(res => {
+      console.log({ ...res.headers });
+      return res;
+    });
+  };
+}
+
+function createMatches(filter: ProxyOptions['filter']): ProxyRequestFilter {
+  switch (true) {
+    case Array.isArray(filter):
+      return url => filter.some(item => url.pathname.startsWith(item));
+
+    case typeof filter === 'string':
+      return url => url.pathname.startsWith(filter);
+
+    case typeof filter === 'function':
+      return filter;
+
+    default:
+      return stubFalse;
+  }
+}
+
+function stubFalse() {
+  return false;
+}