#228 - Basic Hello World Slack Command Bot

node/slack-command-bot/.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
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+*.tgz
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+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variable files
+.env
+.env.development.local
+.env.test.local
+.env.production.local
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+out
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+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
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+.vuepress/dist
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+.temp
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+.tern-port
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+.vscode-test
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+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*

node/slack-command-bot/.prettierrc.json

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+{
+  "trailingComma": "es5",
+  "tabWidth": 2,
+  "semi": true,
+  "singleQuote": true
+}

node/slack-command-bot/README.md

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+# 🤖 Node.js Slack Command Bot Function
+
+Simple command bot using Slack API
+
+## 🧰 Usage
+
+### POST /
+
+A endpoint for you slack command that returns a hello world! message as response.
+
+#### Parameters
+
+| Name                      | Description                      | Location | Type   | Sample Value                                                                              |
+| ------------------------- | -------------------------------- | -------- | ------ | ----------------------------------------------------------------------------------------- |
+| x-slack-signature         | Signature of the request payload | Header   | string | `v0=a...3`                                                                                |
+| x-slack-request-timestamp | Timestamp of the request payload | Header   | string | `1531420618`                                                                              |
+| JSON Body                 | Request payload                  | Body     | Object | See [Slack docs](https://api.slack.com/interactivity/slash-commands#app_command_handling) |
+
+**Response**
+
+Sample `200` Response:
+
+```text
+Hello, World!
+```
+
+Sample `400` Response:
+
+```json
+{
+  "ok": false,
+  "error": "Missing required fields: x-slack-signature"
+}
+```
+
+## ⚙️ Configuration
+
+| Setting           | Value         |
+| ----------------- | ------------- |
+| Runtime           | Node (18.0)   |
+| Entrypoint        | `src/main.js` |
+| Build Commands    | `npm install` |
+| Permissions       | `any`         |
+| Timeout (Seconds) | 15            |
+
+## 🔒 Environment Variables
+
+### SLACK_SIGNING_SECRET
+
+Signing secret of you slack app.
+
+| Question      | Answer                                                                             |
+| ------------- | ---------------------------------------------------------------------------------- |
+| Required      | Yes                                                                                |
+| Sample Value  | `b33...156`                                                                        |
+| Documentation | [Slack Docs](https://api.slack.com/interactivity/slash-commands#creating_commands) |

node/slack-command-bot/package.json

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+{
+  "name": "slack-command-bot",
+  "version": "1.0.0",
+  "description": "",
+  "main": "src/main.js",
+  "type": "module",
+  "scripts": {
+    "format": "prettier --write ."
+  },
+  "dependencies": {
+    "crypto": "^1.0.1"
+  },
+  "devDependencies": {
+    "prettier": "^3.0.0"
+  }
+}

node/slack-command-bot/src/main.js

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+import { throwIfMissing, throwIfRequestNotValid } from './utils.js';
+
+export default async ({ req, res, log, error }) => {
+  throwIfMissing(process.env, ['SLACK_SIGNING_SECRET']);
+
+  try {
+    throwIfMissing(req.headers, [
+      'x-slack-request-timestamp',
+      'x-slack-signature',
+    ]);
+    throwIfRequestNotValid(req);
+  } catch (err) {
+    error(err.message);
+    return res.send({ ok: false, error: err.message }, 400);
+  }
+
+  log('Valid Request');
+  return res.send('Hello World!');
+};

node/slack-command-bot/src/utils.js

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+import crypto from 'crypto';
+
+/**
+ * Throws an error if any of the keys are missing from the object
+ * @param {*} obj
+ * @param {string[]} keys
+ * @throws {Error}
+ */
+export function throwIfMissing(obj, keys) {
+  const missing = [];
+  for (let key of keys) {
+    if (!(key in obj) || !obj[key]) {
+      missing.push(key);
+    }
+  }
+  if (missing.length > 0) {
+    throw new Error(`Missing required fields: ${missing.join(', ')}`);
+  }
+}
+
+/**
+ * Throws an error if incoming request is not valid
+ * @param {*} req
+ * @throws {Error}
+ */
+export function throwIfRequestNotValid(req) {
+  const timestamp = req.headers['x-slack-request-timestamp'];
+  const signature = req.headers['x-slack-signature'];
+
+  if (Math.abs(Date.now() / 1000 - timestamp) > 60 * 5) {
+    throw new Error('Invalid request: replay attack');
+  }
+
+  const signatureBaseString = `v0:${timestamp}:${req.bodyRaw}`;
+  const hmac = crypto.createHmac('sha256', process.env['SLACK_SIGNING_SECRET']);
+  hmac.update(signatureBaseString);
+
+  const expectedSignature = `v0=${hmac.digest('hex')}`;
+  if (expectedSignature !== signature) {
+    throw new Error('Invalid request: incorrect signature');
+  }
+}