refactor: replace `github-app.ts` with `@github/app`

src/@types/@octokit/app/index.d.ts

@@ -0,0 +1,15 @@
+declare module '@octokit/app' {
+  interface Options {
+    id: number,
+    privateKey: string
+  }
+
+  declare class App {
+    constructor (options: Options)
+
+    public getSignedJsonWebToken(): string
+    public getInstallationAccessToken({installationId: number}): Promise<string>
+  }
+
+  export = App
+}

src/application.ts

@@ -1,3 +1,4 @@
+import OctokitApp from '@octokit/app'
 import { WebhookEvent } from '@octokit/webhooks'
 import express from 'express'
 import { EventEmitter } from 'promise-events'
@@ -9,7 +10,7 @@ import { logger } from './logger'
 import { LoggerWithTarget, wrapLogger } from './wrap-logger'
 
 export interface Options {
-  app: () => string
+  app: OctokitApp
   cache: Cache
   router?: express.Router
   catchErrors?: boolean
@@ -29,7 +30,7 @@ function isUnauthenticatedEvent (event: WebhookEvent) {
  */
 export class Application {
   public events: EventEmitter
-  public app: () => string
+  public app: OctokitApp
   public cache: Cache
   public router: express.Router
   public log: LoggerWithTarget
@@ -198,18 +199,15 @@ export class Application {
       const installationTokenTTL = parseInt(process.env.INSTALLATION_TOKEN_TTL || '3540', 10)
 
       return this.cache.wrap(`app:${id}`, async () => {
-        const installation = GitHubAPI({
+        return GitHubAPI({
+          auth: async () => {
+            const accessToken = await this.app.getInstallationAccessToken({ installationId: id })
+            return `token ${accessToken}`
+          },
           baseUrl: process.env.GHE_HOST && `https://${process.env.GHE_HOST}/api/v3`,
           debug: process.env.LOG_LEVEL === 'trace',
           logger: log.child({ name: 'github', installation: String(id) })
         })
-
-        log.trace(`creating token for installation`)
-        installation.authenticate({ type: 'app', token: this.app() })
-
-        const response = await installation.apps.createInstallationToken({ installation_id: id })
-        installation.authenticate({ type: 'token', token: response.data.token })
-        return installation
       }, { ttl: installationTokenTTL })
     }
 
@@ -220,7 +218,7 @@ export class Application {
     })
 
     github.authenticate({
-      token: this.githubToken ? this.githubToken : this.app(),
+      token: this.githubToken ? this.githubToken : this.app.getSignedJsonWebToken(),
       type: 'app'
     })
 

src/github-app.ts

@@ -1,19 +0,0 @@
-import jwt from 'jsonwebtoken'
-
-export const createApp = (options: AppOptions) => {
-  return () => {
-    const payload = {
-      exp: Math.floor(Date.now() / 1000) + 60,  // JWT expiration time
-      iat: Math.floor(Date.now() / 1000),       // Issued at time
-      iss: options.id                           // GitHub App ID
-    }
-
-    // Sign with RSA SHA256
-    return jwt.sign(payload, options.cert, { algorithm: 'RS256' })
-  }
-}
-
-export interface AppOptions {
-  id: number
-  cert: string
-}

src/index.ts

@@ -1,10 +1,11 @@
+import OctokitApp from '@octokit/app'
 import Webhooks, { WebhookEvent } from '@octokit/webhooks'
 import Logger from 'bunyan'
 import express from 'express'
+
 import { Application } from './application'
 import { createDefaultCache } from './cache'
 import { Context } from './context'
-import { createApp } from './github-app'
 import { logger } from './logger'
 import { resolve } from './resolver'
 import { createServer } from './server'
@@ -30,7 +31,7 @@ export class Probot {
 
   private options: Options
   private apps: Application[]
-  private app: () => string
+  private app?: OctokitApp
   private githubToken?: string
 
   constructor (options: Options) {
@@ -40,11 +41,12 @@ export class Probot {
     this.logger = logger
     this.apps = []
     this.webhook = new Webhooks({ path: options.webhookPath, secret: options.secret })
-    if (options.githubToken) {
     this.githubToken = options.githubToken
-      this.app = () => ''
+    if (this.options.id) {
-    } else {
+      this.app = new OctokitApp({
-      this.app = createApp({ id: options.id!, cert: options.cert! })
+        id: options.id as number,
+        privateKey: options.cert as string
+      })
     }
     this.server = createServer({ webhook: this.webhook.middleware, logger })
 
@@ -81,7 +83,11 @@ export class Probot {
     if (typeof appFn === 'string') {
       appFn = resolve(appFn) as ApplicationFunction
     }
-    const app = new Application({ app: this.app, cache, githubToken: this.githubToken })
+    const app = new Application({
+      app: this.app as OctokitApp,
+      cache,
+      githubToken: this.githubToken
+    })
 
     // Connect the router from the app to the server
     this.server.use(app.router)
@@ -131,6 +137,7 @@ export interface Options {
   githubToken?: string,
   webhookProxy?: string,
   port?: number
+
 }
 
 export { Logger, Context, Application }