From 5f575e4c5d617825a0f1d377d90e6e3c10c52452 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Thu, 24 Nov 2022 15:07:58 +0100
Subject: [PATCH 1/2] Move the `validateGitHubWebHook` function into its own
 file

That way, things are organized better, and easier to test locally, too.

This commit is best viewed with `--color-moved`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 LeaveMeAloneGitHubApp/index.js                | 28 +------------------
 .../validate-github-webhook.js                | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 27 deletions(-)
 create mode 100644 LeaveMeAloneGitHubApp/validate-github-webhook.js

diff --git a/LeaveMeAloneGitHubApp/index.js b/LeaveMeAloneGitHubApp/index.js
index b073d948..e7357840 100644
--- a/LeaveMeAloneGitHubApp/index.js
+++ b/LeaveMeAloneGitHubApp/index.js
@@ -1,30 +1,4 @@
-const crypto = require('crypto')
-
-/** Validates the signature added by GitHub */
-const validateGitHubWebHook = (context) => {
-    const secret = process.env['GITHUB_WEBHOOK_SECRET']
-    if (!secret) {
-        throw new Error('Webhook secret not configured')
-    }
-    if (context.req.method !== 'POST') {
-        throw new Error(`Unexpected method: ${context.req.method}`)
-    }
-    if (context.req.headers['content-type'] !== 'application/json') {
-        throw new Error(`Unexpected content type: ${context.req.headers['content-type']}`)
-    }
-    const signature = context.req.headers['x-hub-signature-256']
-    if (!signature) {
-        throw new Error('Missing X-Hub-Signature')
-    }
-    const sha256 = signature.match(/^sha256=(.*)/)
-    if (!sha256) {
-        throw new Error(`Unexpected X-Hub-Signature format: ${signature}`)
-    }
-    const computed = crypto.createHmac('sha256', secret).update(context.req.rawBody).digest('hex')
-    if (sha256[1] !== computed) {
-        throw new Error('Incorrect X-Hub-Signature')
-    }
-}
+const validateGitHubWebHook = require('./validate-github-webhook')
 
 /** Sends a JWT-authenticated GitHub API request */
 const gitHubApiRequestAsApp = require('./github-api-request-as-app')
diff --git a/LeaveMeAloneGitHubApp/validate-github-webhook.js b/LeaveMeAloneGitHubApp/validate-github-webhook.js
new file mode 100644
index 00000000..ada3cc56
--- /dev/null
+++ b/LeaveMeAloneGitHubApp/validate-github-webhook.js
@@ -0,0 +1,28 @@
+const crypto = require('crypto')
+
+/** Validates the signature added by GitHub */
+module.exports = (context) => {
+    const secret = process.env['GITHUB_WEBHOOK_SECRET']
+    if (!secret) {
+        throw new Error('Webhook secret not configured')
+    }
+    if (context.req.method !== 'POST') {
+        throw new Error(`Unexpected method: ${context.req.method}`)
+    }
+    if (context.req.headers['content-type'] !== 'application/json') {
+        throw new Error(`Unexpected content type: ${context.req.headers['content-type']}`)
+    }
+    const signature = context.req.headers['x-hub-signature-256']
+    if (!signature) {
+        throw new Error('Missing X-Hub-Signature')
+    }
+    const sha256 = signature.match(/^sha256=(.*)/)
+    if (!sha256) {
+        throw new Error(`Unexpected X-Hub-Signature format: ${signature}`)
+    }
+    const computed = crypto.createHmac('sha256', secret).update(context.req.rawBody).digest('hex')
+    if (sha256[1] !== computed) {
+        throw new Error('Incorrect X-Hub-Signature')
+    }
+}
+

From d319ff1dbe43b07bbaba434d6d0a06deaafa986f Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Thu, 24 Nov 2022 22:18:03 +0100
Subject: [PATCH 2/2] Introduce short-and-sweet functions to send an HTTP
 response

By calling `return ok(...)` or `return withStatus(...)`, it is now
really easy and concise to exit from the Azure Function by sending an
HTTP response.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 LeaveMeAloneGitHubApp/index.js | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/LeaveMeAloneGitHubApp/index.js b/LeaveMeAloneGitHubApp/index.js
index e7357840..03eef184 100644
--- a/LeaveMeAloneGitHubApp/index.js
+++ b/LeaveMeAloneGitHubApp/index.js
@@ -4,15 +4,23 @@ const validateGitHubWebHook = require('./validate-github-webhook')
 const gitHubApiRequestAsApp = require('./github-api-request-as-app')
 
 module.exports = async function (context, req) {
+    const withStatus = (status, headers, body) => {
+        context.res = {
+            status,
+            headers,
+            body
+        }
+    }
+
+    const ok = (body) => {
+        withStatus(undefined, undefined, body)
+    }
+
     try {
         validateGitHubWebHook(context)
     } catch (e) {
         context.log(e)
-        context.res = {
-            status: 403,
-            body: `Go away, you are not a valid GitHub webhook: ${e}`,
-        }
-        return
+        return withStatus(403, undefined, `Go away, you are not a valid GitHub webhook: ${e}`)
     }
 
     if (req.headers['x-github-event'] === 'installation' && req.body.action === 'created') {
@@ -26,10 +34,7 @@ module.exports = async function (context, req) {
             }
         } catch (e) {
             context.log(e)
-            context.res = {
-                status: 500,
-                body: `Error:\n${e}`,
-            }
+            return withStatus(500, undefined, `Error:\n${e}`)
         }
         return
     }
@@ -39,8 +44,5 @@ module.exports = async function (context, req) {
     context.log("Got body")
     context.log(req.body)
 
-    context.res = {
-        // status: 200, /* Defaults to 200 */
-        body: `Received event ${req.headers["x-github-event"]}`
-    }
+    ok(`Received event ${req.headers["x-github-event"]}`)
 }