feat: add hooks to before and after requests (#149)

Author: blacha

src/__test__/wrap.test.ts

@@ -6,13 +6,15 @@ import { lf } from '../function.js';
 import { LambdaRequest } from '../request.js';
 import { LambdaHttpRequest } from '../http/request.http.js';
 import { LambdaHttpResponse } from '../http/response.http.js';
-import { AlbExample, ApiGatewayExample, clone, CloudfrontExample } from './examples.js';
+import { AlbExample, ApiGatewayExample, clone, CloudfrontExample, UrlExample } from './examples.js';
 import { fakeLog } from './log.js';
 import { HttpMethods } from '../http/router.js';
+import { UrlResult } from '../http/request.url.js';
 
 function assertAlbResult(x: unknown): asserts x is ALBResult {}
 function assertCloudfrontResult(x: unknown): asserts x is CloudFrontResultResponse {}
 function assertsApiGatewayResult(x: unknown): asserts x is APIGatewayProxyStructuredResultV2 {}
+function assertsUrlResult(x: unknown): asserts x is UrlResult {}
 
 o.spec('LambdaWrap', () => {
   const fakeContext = {} as Context;
@@ -160,6 +162,35 @@ o.spec('LambdaWrap', () => {
     o(body.id).equals(requests[0].id);
   });
 
+  o('should respond to function url events', async () => {
+    const fn = lf.http(fakeLog);
+    const req = clone(UrlExample);
+    req.rawPath = '/v1/tiles/aerial/EPSG:3857/6/3/41.json';
+    fn.router.get('/v1/tiles/:tileSet/:projection/:z/:x/:y.json', fakeLambda);
+    const ret = await new Promise((resolve) => fn(req, fakeContext, (a, b) => resolve(b)));
+
+    assertsUrlResult(ret);
+    o(ret.statusCode).equals(200);
+    o(ret.isBase64Encoded).equals(false);
+    o(ret.headers?.['content-type']).deepEquals('application/json');
+
+    const body = JSON.parse(ret.body ?? '');
+    o(body.message).equals('ok');
+    o(body.status).equals(200);
+    o(body.id).equals(requests[0].id);
+  });
+
+  o('should handle thrown http responses', async () => {
+    const fn = lf.http(fakeLog);
+    fn.router.all('*', () => {
+      throw new LambdaHttpResponse(400, 'Error');
+    });
+    const ret = await new Promise((resolve) => fn(ApiGatewayExample, fakeContext, (a, b) => resolve(b)));
+
+    assertsUrlResult(ret);
+    o(ret.statusCode).equals(400);
+  });
+
   o('should handle http exceptions', async () => {
     const fn = lf.http(fakeLog);
     fn.router.all('*', () => {

src/function.ts

@@ -33,7 +33,7 @@ const hash = process.env.GIT_HASH;
 const versionInfo = { version, hash };
 
 /** Run the request catching any errors */
-async function runFunction<T extends LambdaRequest, K>(
+export async function runFunction<T extends LambdaRequest, K>(
   req: T,
   fn: (req: T) => K | Promise<K>,
 ): Promise<K | LambdaHttpResponse> {

src/http/__test__/router.hook.test.ts

@@ -0,0 +1,98 @@
+import { Context } from 'aws-lambda';
+import o from 'ospec';
+import sinon from 'sinon';
+import { UrlExample } from '../../__test__/examples.js';
+import { fakeLog } from '../../__test__/log.js';
+import { LambdaUrlRequest } from '../request.url.js';
+import { LambdaHttpResponse } from '../response.http.js';
+import { Router } from '../router.js';
+
+o.spec('RouterHook', () => {
+  const fakeContext = {} as Context;
+  const sandbox = sinon.createSandbox();
+  const req = new LambdaUrlRequest(UrlExample, fakeContext, fakeLog);
+
+  o.afterEach(() => sandbox.restore());
+
+  o.spec('request', () => {
+    o('should run before every request', async () => {
+      const r = new Router();
+
+      const hook = sandbox.stub();
+      r.hook('request', hook);
+
+      const res = await r.handle(req);
+
+      o(res.status).equals(404);
+      o(hook.calledOnce).equals(true);
+
+      const resB = await r.handle(req);
+      o(resB.status).equals(404);
+      o(hook.calledTwice).equals(true);
+    });
+
+    o('should allow request hooks to make responses', async () => {
+      const r = new Router();
+      r.hook('request', () => {
+        return new LambdaHttpResponse(200, 'ok');
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(200);
+    });
+    o('should allow request hooks to throw responses', async () => {
+      const r = new Router();
+      r.hook('request', () => {
+        throw new LambdaHttpResponse(500, 'ok');
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(500);
+      o(res.statusDescription).equals('ok');
+    });
+    o('should catch unhandled exceptions', async () => {
+      const r = new Router();
+      r.hook('request', (req) => {
+        req.path = ''; // Path is readonly
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(500);
+      o(res.statusDescription).equals('Internal Server Error');
+    });
+  });
+
+  o.spec('response', () => {
+    o('should allow overriding of response', async () => {
+      const r = new Router();
+      r.hook('response', (req, res) => {
+        o(res.status).equals(404);
+        res.status = 200;
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(200);
+    });
+
+    o('should allow throwing of errors', async () => {
+      const r = new Router();
+      r.hook('response', () => {
+        throw new LambdaHttpResponse(400, 'ok');
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(400);
+    });
+
+    o('should catch unhandled exceptions', async () => {
+      const r = new Router();
+      r.hook('response', (req) => {
+        req.path = ''; // Path is readonly
+      });
+
+      const res = await r.handle(req);
+      o(res.status).equals(500);
+      o(res.statusDescription).equals('Internal Server Error');
+    });
+  });
+});

src/http/router.ts

@@ -1,10 +1,27 @@
-import { execute } from '../function.js';
+import { execute, runFunction } from '../function.js';
 import { LambdaHttpRequest, RequestTypes } from './request.http.js';
 import { LambdaHttpResponse } from './response.http.js';
 
-export type Route<T extends RequestTypes> = (
+export type Route<T extends RequestTypes = RequestTypes> = (
   req: LambdaHttpRequest<T>,
 ) => Promise<LambdaHttpResponse> | LambdaHttpResponse | void;
+
+export type RouteResponse<T extends RequestTypes> = (
+  req: LambdaHttpRequest<T>,
+  res: LambdaHttpResponse,
+) => Promise<void> | void;
+
+export type RouteHooks = {
+  /** Before the request is executed */
+  request: Route<RequestTypes>;
+  /** Before the response is returned to the lambda */
+  response: RouteResponse<RequestTypes>;
+};
+
+export type HookRecord<T extends RouteHooks> = {
+  [K in keyof T]: T[K][];
+};
+
 export type HttpMethods = 'DELETE' | 'GET' | 'HEAD' | 'PATCH' | 'POST' | 'PUT' | 'OPTIONS' | 'ALL';
 export class Router {
   routes: {
@@ -15,6 +32,13 @@ export class Router {
     fn: Route<any>;
   }[] = [];
 
+  hooks: HookRecord<RouteHooks> = {
+    /** Hooks to be run before every request */
+    request: [],
+    /** Hooks to be run after every request */
+    response: [],
+  };
+
   register<T extends RequestTypes>(method: HttpMethods, path: string, fn: Route<T>): void {
     // Stolen from https://github.com/kwhitley/itty-router
     const regex = RegExp(
@@ -30,6 +54,16 @@ export class Router {
     this.routes.push({ path: regex, method, fn });
   }
 
+  /**
+   * Attach a hook to the router
+   * @param name hook to attach too
+   * @param cb Function to call on hook
+   */
+  hook<K extends keyof RouteHooks>(name: K, cb: RouteHooks[K]): void {
+    this.hooks[name].push(cb);
+  }
+
+  /** Register a route for all HTTP types, GET, POST, HEAD, etc... */
   all<T extends RequestTypes>(path: string, fn: Route<T>): void {
     return this.register('ALL', path, fn);
   }
@@ -55,18 +89,42 @@ export class Router {
     return this.register('PUT', path, fn);
   }
 
+  /** After a route has finished processing run the response hooks on the request/response pair */
+  async after(req: LambdaHttpRequest, response: LambdaHttpResponse): Promise<LambdaHttpResponse> {
+    try {
+      for (const hook of this.hooks.response) await hook(req, response);
+    } catch (e) {
+      if (LambdaHttpResponse.is(e)) return e;
+      req.set('err', e);
+      return new LambdaHttpResponse(500, 'Internal Server Error');
+    }
+    return response;
+  }
+
+  /**
+   * Handle a incoming request
+   *
+   * Request flow: hook.request(req) -> requestHandler(req) -> hook.response(req, res)
+   */
   async handle(req: LambdaHttpRequest): Promise<LambdaHttpResponse> {
+    // On before request
+    for (const hook of this.hooks.request) {
+      const res = await runFunction(req, hook);
+      // If a hook returns a response return the response to the user
+      if (res) return this.after(req, res);
+    }
+
     for (const r of this.routes) {
       if (r.method !== 'ALL' && req.method !== r.method) continue;
       const m = req.path.match(r.path);
       if (m) {
         // TODO this should ideally be validated
         req.params = m.groups;
-        const ret = await execute(req, r.fn);
-        if (ret) return ret;
+        const res = await execute(req, r.fn);
+        if (res) return this.after(req, res);
       }
     }
 
-    return new LambdaHttpResponse(404, 'Not found');
+    return this.after(req, new LambdaHttpResponse(404, 'Not found'));
   }
 }