Add exportBackupFile in MessageBus

src/sdk/MessageBus.ts

@@ -644,6 +644,39 @@ export default class MessageBus {
     });
   }
 
+  public exportBackupFile(): Promise<any> {
+    return new Promise<any>((resolve: (backupFile: any) => void, reject: (error: string) => void) => {
+      this.checkToken().then(() => {
+        const messageId = `EXPORT_BACKUP_${uuidv4()}`;
+
+        const unsubscribe = EventBus.getInstance().on('BACKUP_RETRIEVED', (responseId: string, backupFile: any) => {
+          if (responseId !== messageId) {
+            return;
+          }
+          unsubscribe();
+          resolve(backupFile);
+        });
+
+        const unsubscribeError = EventBus.getInstance().on('ERROR_BACKUP_RETRIEVED', (responseId: string, error: string) => {
+          if (responseId !== messageId) {
+            return;
+          }
+          unsubscribeError();
+          reject(error);
+        });
+
+        const user = User.getInstance();
+        const accessToken = user.getAccessToken()!;
+
+        this.sendMessage({
+          type: 'EXPORT_BACKUP',
+          accessToken,
+          messageId
+        });
+      }).catch(reject);
+    });
+  }
+
   public verifyMerkleProof(merkleProof: string, documentHash: string): Promise<boolean> {
     return new Promise<boolean>((resolve: (isValid: boolean) => void, reject: (error: string) => void) => {
       this.checkToken().then(() => {