[core] Return json or binary based on Accept header

src/api/auth.controller.ts

@@ -2,19 +2,27 @@ import {
   Body,
   Controller,
   Get,
+  Headers,
   Post,
+  Req,
   Res,
   StreamableFile,
 } from '@nestjs/common';
 import { UnprocessableEntityException } from '@nestjs/common/exceptions/unprocessable-entity.exception';
-import { ApiOperation, ApiSecurity, ApiTags } from '@nestjs/swagger';
-import { Response } from 'express';
+import {
+  ApiOperation,
+  ApiResponse,
+  ApiSecurity,
+  ApiTags,
+} from '@nestjs/swagger';
+import { Request, Response } from 'express';
 
 import { SessionManager } from '../core/abc/manager.abc';
 import { WhatsappSession } from '../core/abc/session.abc';
 import { OTPRequest, RequestCodeRequest } from '../structures/auth.dto';
 import { WAHASessionStatus } from '../structures/enums.dto';
-import { SessionApiParam, SessionParam } from './helpers';
+import { Base64File } from '../structures/files.dto';
+import { ApiFileAcceptHeader, SessionApiParam, SessionParam } from './helpers';
 
 @ApiSecurity('api_key')
 @Controller('api/:session/auth')
@@ -24,19 +32,30 @@ class AuthController {
 
   @Get('qr')
   @SessionApiParam
+  @ApiFileAcceptHeader()
   @ApiOperation({
     summary: 'Get QR code for pairing WhatsApp Web.',
   })
   async getQR(
     @Res({ passthrough: true }) res: Response,
+    // We don't use @Headers and work directly with @Req here to avoid adding it to Swagger
+    @Req() req: Request,
     @SessionParam session: WhatsappSession,
-  ) {
+  ): Promise<Base64File | StreamableFile> {
     if (session.status != WAHASessionStatus.SCAN_QR_CODE) {
       const err = `Can get QR code only in SCAN_QR_CODE status. The current status is '${session.status}'`;
       throw new UnprocessableEntityException(err);
     }
 
     const buffer = await session.getQR();
+    const accept = req.headers['accept'];
+    if (accept == 'application/json') {
+      return {
+        mimetype: 'image/png',
+        data: buffer.toString('base64'),
+      };
+    }
+
     const file = new StreamableFile(buffer);
     res.set({
       'Content-Type': 'image/png',

src/api/helpers.ts

@@ -1,5 +1,5 @@
 import { Injectable, Param, PipeTransform } from '@nestjs/common';
-import { ApiParam } from '@nestjs/swagger';
+import { ApiParam, ApiResponse } from '@nestjs/swagger';
 
 import { SessionManager } from '../core/abc/manager.abc';
 import { WhatsappSession } from '../core/abc/session.abc';
@@ -36,3 +36,32 @@ export const SessionApiParam = ApiParam({
  @SessionParam session: WhatsappSession,
  */
 export const SessionParam = Param('session', SessionPipe);
+
+export function ApiFileAcceptHeader() {
+  return ApiResponse({
+    status: 200,
+    content: {
+      'image/png': {
+        schema: {
+          type: 'string',
+          format: 'binary',
+        },
+      },
+      'application/json': {
+        schema: {
+          type: 'object',
+          properties: {
+            data: {
+              type: 'string',
+              format: 'base64',
+            },
+            mimetype: {
+              type: 'string',
+              example: 'image/png',
+            },
+          },
+        },
+      },
+    },
+  });
+}

src/structures/files.dto.ts

@@ -1,7 +1,7 @@
 import { ApiProperty } from '@nestjs/swagger';
 export class Base64File {
-  data: string;
   mimetype: string;
+  data: string;
 }
 
 export class RemoteFile {