backend-common: Implement readUrl for gitlab

Signed-off-by: Johan Haals <johan.haals@gmail.com>

packages/backend-common/src/reading/GitlabUrlReader.test.ts

@@ -79,7 +79,7 @@ describe('GitlabUrlReader', () => {
   const worker = setupServer();
   msw.setupDefaultHandlers(worker);
 
-  describe('implementation', () => {
+  describe('read', () => {
     beforeEach(() => {
       worker.use(
         rest.get('*/api/v4/projects/:name', (_, res, ctx) =>
@@ -180,6 +180,53 @@ describe('GitlabUrlReader', () => {
     });
   });
 
+  describe('readUrl', () => {
+    const [{ reader }] = GitlabUrlReader.factory({
+      config: new ConfigReader({}),
+      logger,
+      treeResponseFactory,
+    });
+
+    it('should throw NotModified on HTTP 304', async () => {
+      worker.use(
+        rest.get('*/api/v4/projects/:name', (_, res, ctx) =>
+          res(ctx.status(200), ctx.json({ id: 12345 })),
+        ),
+        rest.get('*', (req, res, ctx) => {
+          expect(req.headers.get('If-None-Match')).toBe('999');
+          return res(ctx.status(304));
+        }),
+      );
+
+      await expect(
+        reader.readUrl!(
+          'https://gitlab.com/groupA/teams/teamA/subgroupA/repoA/-/blob/branch/my/path/to/file.yaml',
+          {
+            etag: '999',
+          },
+        ),
+      ).rejects.toThrow(NotModifiedError);
+    });
+
+    it('should return etag in response', async () => {
+      worker.use(
+        rest.get('*/api/v4/projects/:name', (_, res, ctx) =>
+          res(ctx.status(200), ctx.json({ id: 12345 })),
+        ),
+        rest.get('*', (req, res, ctx) => {
+          return res(ctx.status(200), ctx.set('ETag', '999'), ctx.body('foo'));
+        }),
+      );
+
+      const result = await reader.readUrl!(
+        'https://gitlab.com/groupA/teams/teamA/subgroupA/repoA/-/blob/branch/my/path/to/file.yaml',
+      );
+      expect(result.etag).toBe('999');
+      const content = await result.buffer();
+      expect(content.toString()).toBe('foo');
+    });
+  });
+
   describe('readTree', () => {
     const archiveBuffer = fs.readFileSync(
       path.resolve('src', 'reading', '__fixtures__', 'gitlab-archive.tar.gz'),

packages/backend-common/src/reading/GitlabUrlReader.ts

@@ -34,6 +34,8 @@ import {
   SearchOptions,
   SearchResponse,
   UrlReader,
+  ReadUrlResponse,
+  ReadUrlOptions,
 } from './types';
 
 export class GitlabUrlReader implements UrlReader {
@@ -54,20 +56,37 @@ export class GitlabUrlReader implements UrlReader {
   ) {}
 
   async read(url: string): Promise<Buffer> {
+    const response = await this.readUrl(url);
+    return response.buffer();
+  }
+
+  async readUrl(
+    url: string,
+    options?: ReadUrlOptions,
+  ): Promise<ReadUrlResponse> {
     const builtUrl = await getGitLabFileFetchUrl(url, this.integration.config);
 
     let response: Response;
     try {
-      response = await fetch(
-        builtUrl,
-        getGitLabRequestOptions(this.integration.config),
-      );
+      response = await fetch(builtUrl, {
+        headers: {
+          ...getGitLabRequestOptions(this.integration.config).headers,
+          ...(options?.etag && { 'If-None-Match': options.etag }),
+        },
+      });
     } catch (e) {
       throw new Error(`Unable to read ${url}, ${e}`);
     }
 
+    if (response.status === 304) {
+      throw new NotModifiedError();
+    }
+
     if (response.ok) {
-      return Buffer.from(await response.text());
+      const etag = response.headers.get('ETag')
+        ? response.headers.get('ETag')!
+        : undefined;
+      return { buffer: async () => Buffer.from(await response.text()), etag };
     }
 
     const message = `${url} could not be read as ${builtUrl}, ${response.status} ${response.statusText}`;