Set default branch to main

Previously, image uploads depend on the user's default branch.
Now, we set the branch for image upload to be `main`. Images will 
be uploaded to `main` as a result.

---------

Co-authored-by: Chee Hong <[email protected]>

src/app/core/services/github.service.ts

@@ -16,6 +16,7 @@ import {
   FetchLabelsQuery
 } from '../../../../graphql/graphql-types';
 import { AppConfig } from '../../../environments/environment';
+import { throwIfFalse } from '../../shared/lib/custom-ops';
 import { getNumberOfPages } from '../../shared/lib/github-paginator-parser';
 import { IssueComment } from '../models/comment.model';
 import { GithubUser } from '../models/github-user.model';
@@ -35,7 +36,9 @@ import { LoggingService } from './logging.service';
 const { Octokit } = require('@octokit/rest');
 const CATCHER_ORG = 'CATcher-org';
 const CATCHER_REPO = 'CATcher';
+const BRANCH = 'main';
 const UNABLE_TO_OPEN_IN_BROWSER = 'Unable to open this issue in Browser';
+const BRANCH_CREATION_FAILED = `Unable to create ${BRANCH} branch.`;
 function getSettingsUrl(org: string, repoName: string): string {
   return `https://raw.githubusercontent.com/${org}/${repoName}/master/settings.json`;
 }
@@ -201,6 +204,84 @@ export class GithubService {
     octokit.repos.createForAuthenticatedUser({ name: name });
   }
 
+  /**
+   * Creates the `main` branch for the current repository.
+   */
+  createBranch() {
+    return this.getDefaultBranch().pipe(
+      mergeMap((res) => this.getBranchHeadInfo(res)),
+      map((res) => res.data.object.sha),
+      mergeMap((sha: string) => this.createBranchFromCommit(sha)),
+      mergeMap(() => this.isMainBranchPresent()),
+      throwIfFalse(
+        (isBranchPresent: boolean) => isBranchPresent,
+        () => new Error(BRANCH_CREATION_FAILED)
+      )
+    );
+  }
+
+  /**
+   * Creates the `main` branch for the current repository,
+   * from the commit with the given SHA.
+   */
+  createBranchFromCommit(commitSha: string) {
+    return from(
+      octokit.git.createRef({
+        owner: ORG_NAME,
+        repo: REPO,
+        ref: `refs/heads/${BRANCH}`,
+        sha: commitSha
+      })
+    );
+  }
+
+  /**
+   * Get the default branch of the specified repository.
+   * @param owner The owner of the repository.
+   * @param repo The name of the repository.
+   */
+  getDefaultBranch(): Observable<string> {
+    return from(
+      octokit.repos.get({
+        owner: ORG_NAME,
+        repo: REPO
+      })
+    ).pipe(map((res: any) => res.data.default_branch));
+  }
+
+  /**
+   * Get information of the head of the given branch name,
+   * in the current repository.
+   * @param branch The name of the branch.
+   */
+  getBranchHeadInfo(branch: string): Observable<any> {
+    return from(
+      octokit.git.getRef({
+        owner: ORG_NAME,
+        repo: REPO,
+        ref: `heads/${branch}`
+      })
+    );
+  }
+
+  /**
+   * Checks if the repo already has the branch `main`.
+   */
+  isMainBranchPresent(): Observable<boolean> {
+    return from(
+      octokit.git.getRef({
+        owner: ORG_NAME,
+        repo: REPO,
+        ref: `heads/${BRANCH}`
+      })
+    ).pipe(
+      map((res: any) => res.status !== ERRORCODE_NOT_FOUND),
+      catchError(() => {
+        return of(false);
+      })
+    );
+  }
+
   /**
    * Fetches information about an issue using GraphQL.
    *
@@ -360,6 +441,7 @@ export class GithubService {
       octokit.repos.createOrUpdateFile({
         owner: ORG_NAME,
         repo: REPO,
+        branch: BRANCH,
         path: `files/${filename}`,
         message: 'upload file',
         content: base64String

src/app/core/services/upload.service.ts

@@ -1,6 +1,8 @@
 import { Injectable } from '@angular/core';
-import { throwError } from 'rxjs';
+import { of, throwError } from 'rxjs';
+import { catchError, mergeMap } from 'rxjs/operators';
 import { uuid } from '../../shared/lib/uuid';
+import { ERRORCODE_NOT_FOUND } from './error-handling.service';
 import { GithubService } from './github.service';
 
 const SUPPORTED_VIDEO_FILE_TYPES = ['mp4', 'mov'];
@@ -49,7 +51,21 @@ export class UploadService {
     if (SUPPORTED_FILE_TYPES.includes(fileType.toLowerCase())) {
       base64String = base64String.split(',')[1];
       const onlineFilename = uuid();
-      return this.githubService.uploadFile(`${onlineFilename}.${fileType}`, base64String);
+      const attemptUploadFile = () => this.githubService.uploadFile(`${onlineFilename}.${fileType}`, base64String);
+      return attemptUploadFile().pipe(
+        catchError((err: any) => {
+          if (!(err.status === ERRORCODE_NOT_FOUND)) {
+            return throwError(err);
+          }
+          return of(false);
+        }),
+        mergeMap((isBranchPresent) => {
+          if (isBranchPresent) {
+            return of(isBranchPresent);
+          }
+          return this.githubService.createBranch().pipe(mergeMap(attemptUploadFile));
+        })
+      );
     } else {
       return throwError(FILE_TYPE_SUPPORT_ERROR);
     }