Added download method for returning stream

src/apiClient.ts

@@ -244,4 +244,41 @@ export default class APIClient {
     // Return the raw buffer
     return response.buffer();
   }
+
+  async requestStream(
+    options: RequestOptionsParams
+  ): Promise<NodeJS.ReadableStream> {
+    const req = this.newRequest(options);
+    const controller: AbortController = new AbortController();
+    const timeout = setTimeout(() => {
+      controller.abort();
+      throw new NylasSdkTimeoutError(req.url, this.timeout);
+    }, this.timeout);
+
+    const response = await fetch(req, { signal: controller.signal });
+    clearTimeout(timeout);
+
+    if (typeof response === 'undefined') {
+      throw new Error('Failed to fetch response');
+    }
+
+    // Handle error response
+    if (response.status > 299) {
+      const text = await response.text();
+      let error: Error;
+      try {
+        const parsedError = JSON.parse(text);
+        const camelCaseError = objKeysToCamelCase(parsedError);
+        error = new NylasApiError(camelCaseError, response.status);
+      } catch (e) {
+        throw new Error(
+          `Received an error but could not parse response from the server: ${text}`
+        );
+      }
+
+      throw error;
+    }
+
+    return response.body;
+  }
 }

src/resources/attachments.ts

@@ -62,16 +62,45 @@ export class Attachments extends Resource {
       overrides,
     });
   }
-
+  
   /**
-   * Returns an attachment by ID.
-   * @return The Attachment file in binary format
+   * Download the attachment data
+   *
+   * This method returns a NodeJS.ReadableStream which can be used to stream the attachment data.
+   * This is particularly useful for handling large attachments efficiently, as it avoids loading
+   * the entire file into memory. The stream can be piped to a file stream or used in any other way
+   * that Node.js streams are typically used.
+   * 
+   * @param identifier Grant ID or email account to query
+   * @param attachmentId The id of the attachment to download.
+   * @param queryParams The query parameters to include in the request
+   * @returns {NodeJS.ReadableStream} The ReadableStream containing the file data.
    */
   public download({
     identifier,
     attachmentId,
     queryParams,
     overrides,
+  }: DownloadAttachmentParams & Overrides): Promise<NodeJS.ReadableStream> {
+    return this._getStream({
+      path: `/v3/grants/${identifier}/attachments/${attachmentId}/download`,
+      queryParams,
+      overrides,
+    });
+  }
+
+  /**
+   * Download the attachment as a byte array
+   * @param identifier Grant ID or email account to query
+   * @param attachmentId The id of the attachment to download.
+   * @param queryParams The query parameters to include in the request
+   * @return The raw file data
+   */
+  public downloadBytes({
+    identifier,
+    attachmentId,
+    queryParams,
+    overrides,
   }: DownloadAttachmentParams & Overrides): Promise<Buffer> {
     return super._getRaw({
       path: `/v3/grants/${identifier}/attachments/${attachmentId}/download`,

src/resources/resource.ts

@@ -205,6 +205,19 @@ export class Resource {
       overrides,
     });
   }
+
+  protected _getStream({
+    path,
+    queryParams,
+    overrides,
+  }: FindParams<void>): Promise<NodeJS.ReadableStream> {
+    return this.apiClient.requestStream({
+      method: 'GET',
+      path,
+      queryParams,
+      overrides,
+    });
+  }
 }
 
 type ListYieldReturn<T> = T & {

tests/resources/attachments.spec.ts

@@ -1,5 +1,6 @@
 import APIClient from '../../src/apiClient';
 import { Attachments } from '../../src/resources/attachments';
+import { Readable } from 'stream';
 jest.mock('../src/apiClient');
 
 describe('Attachments', () => {
@@ -16,6 +17,9 @@ describe('Attachments', () => {
     attachments = new Attachments(apiClient);
     apiClient.request.mockResolvedValue({});
     apiClient.requestRaw.mockResolvedValue(Buffer.from(''));
+
+    const mockStream = new Readable();
+    apiClient.requestStream.mockResolvedValue(Promise.resolve(mockStream));
   });
 
   describe('find', () => {
@@ -44,8 +48,34 @@ describe('Attachments', () => {
     });
   });
 
+  describe('downloadBytes', () => {
+    it('should call apiClient.requestRaw with the correct params for downloading an attachment as bytes', async () => {
+      await attachments.downloadBytes({
+        identifier: 'id123',
+        attachmentId: 'attach123',
+        queryParams: {
+          messageId: 'message123',
+        },
+        overrides: {
+          apiUri: 'https://test.api.nylas.com',
+        },
+      });
+
+      expect(apiClient.requestRaw).toHaveBeenCalledWith({
+        method: 'GET',
+        path: '/v3/grants/id123/attachments/attach123/download',
+        queryParams: {
+          messageId: 'message123',
+        },
+        overrides: {
+          apiUri: 'https://test.api.nylas.com',
+        },
+      });
+    });
+  });
+
   describe('download', () => {
-    it('should call apiClient.requestRaw with the correct params for downloading an attachment', async () => {
+    it('should call apiClient.requestStream with the correct params for streaming an attachment', async () => {
       await attachments.download({
         identifier: 'id123',
         attachmentId: 'attach123',
@@ -57,7 +87,7 @@ describe('Attachments', () => {
         },
       });
 
-      expect(apiClient.requestRaw).toHaveBeenCalledWith({
+      expect(apiClient.requestStream).toHaveBeenCalledWith({
         method: 'GET',
         path: '/v3/grants/id123/attachments/attach123/download',
         queryParams: {