ci(docs-infra): change AIO preview server stuff to pull builds from CircleCI

Previously, Travis pushed the build artitfacts to the preview server.
This required us to use JWT to secure the POST request from Travis, to
ensure we couldn't receive malicious builds.

JWT has been deprecated and we are moving our builds to CircleCI.

This commit rewrites the TypeScript part of the preview server that
handles converting build artifact into hosted previews of the docs.

aio/aio-builds-setup/dockerbuild/scripts-js/lib/common/github-pull-requests.ts

@@ -1,46 +1,79 @@
-// Imports
-import {assertNotMissingOrEmpty} from '../common/utils';
+import {assert, assertNotMissingOrEmpty} from '../common/utils';
 import {GithubApi} from './github-api';
 
-// Interfaces - Types
-export interface PullRequest  {
+export interface PullRequest {
   number: number;
   user: {login: string};
   labels: {name: string}[];
 }
 
+export interface FileInfo {
+  sha: string;
+  filename: string;
+}
+
 export type PullRequestState = 'all' | 'closed' | 'open';
 
-// Classes
-export class GithubPullRequests extends GithubApi {
-  // Constructor
-  constructor(githubToken: string, protected repoSlug: string) {
-    super(githubToken);
-    assertNotMissingOrEmpty('repoSlug', repoSlug);
+/**
+ * Access pull requests on GitHub.
+ */
+export class GithubPullRequests {
+  public repoSlug: string;
+
+  /**
+   * Create an instance of this helper
+   * @param api An instance of the Github API helper.
+   * @param githubOrg The organisation on GitHub whose repo we will interrogate.
+   * @param githubRepo The repository on Github with whose PRs we will interact.
+   */
+  constructor(private api: GithubApi, githubOrg: string, githubRepo: string) {
+    assertNotMissingOrEmpty('githubOrg', githubOrg);
+    assertNotMissingOrEmpty('githubRepo', githubRepo);
+    this.repoSlug = `${githubOrg}/${githubRepo}`;
   }
 
-  // Methods - Public
-  public addComment(pr: number, body: string): Promise<void> {
-    if (!(pr > 0)) {
-      throw new Error(`Invalid PR number: ${pr}`);
-    } else if (!body) {
-      throw new Error(`Invalid or empty comment body: ${body}`);
-    }
-
-    return this.post<void>(`/repos/${this.repoSlug}/issues/${pr}/comments`, null, {body});
+  /**
+   * Post a comment on a PR.
+   * @param pr The number of the PR on which to comment.
+   * @param body The body of the comment to post.
+   * @returns A promise that resolves when the comment has been posted.
+   */
+  public addComment(pr: number, body: string) {
+    assert(pr > 0, `Invalid PR number: ${pr}`);
+    assert(!!body, `Invalid or empty comment body: ${body}`);
+    return this.api.post<any>(`/repos/${this.repoSlug}/issues/${pr}/comments`, null, {body});
   }
 
-  public fetch(pr: number): Promise<PullRequest> {
+  /**
+   * Request information about a PR.
+   * @param pr The number of the PR for which to request info.
+   * @returns A promise that is resolves with information about the specified PR.
+   */
+  public fetch(pr: number) {
+    assert(pr > 0, `Invalid PR number: ${pr}`);
     // Using the `/issues/` URL, because the `/pulls/` one does not provide labels.
-    return this.get<PullRequest>(`/repos/${this.repoSlug}/issues/${pr}`);
+    return this.api.get<PullRequest>(`/repos/${this.repoSlug}/issues/${pr}`);
   }
 
-  public fetchAll(state: PullRequestState = 'all'): Promise<PullRequest[]> {
-    console.log(`Fetching ${state} pull requests...`);
-
+  /**
+   * Request information about all PRs that match the given state.
+   * @param state Only retrieve PRs that have this state.
+   * @returns A promise that is resolved with information about the requested PRs.
+   */
+  public fetchAll(state: PullRequestState = 'all') {
     const pathname = `/repos/${this.repoSlug}/pulls`;
     const params = {state};
 
-    return this.getPaginated<PullRequest>(pathname, params);
+    return this.api.getPaginated<PullRequest>(pathname, params);
+  }
+
+  /**
+   * Request a list of files for the given PR.
+   * @param pr The number of the PR for which to request files.
+   * @returns A promise that resolves to an array of file information
+   */
+  public fetchFiles(pr: number) {
+    assert(pr > 0, `Invalid PR number: ${pr}`);
+    return this.api.get<FileInfo[]>(`/repos/${this.repoSlug}/pulls/${pr}/files`);
   }
 }