feat: write an atom feed file

write a atom feed file containing the latest 10 posts

src/services/homepage.js

@@ -1,4 +1,5 @@
 const path = require('path');
+const feedService = require('./feed');
 const listService = require('./list');
 const { fileService } = require('./file');
 const { buildHrefPrefixes } = require('./homepage-href');
@@ -50,6 +51,7 @@ function buildHomepages(postSummaries, outputDirectory, { lang, availableLanguag
     });
     fileService.write(buildFilepath(outputDirectory, pageNumber), html);
   });
+  feedService.build(postSummaryPages[0], lang);
 }
 
 function buildFilepath(outputDirectory, pageNumber){

src/services/homepage.test.js

@@ -1,4 +1,5 @@
 const postsMock = require('../mocks/posts');
+const feedService = require('./feed');
 const { fileService } = require('./file');
 const pageService = require('./page');
 const homepageService = require('./homepage');
@@ -18,6 +19,7 @@ describe('Homepage Service', () => {
     fileService.write = jest.fn();
     fileService.copySync = jest.fn();
     pageService.build = jest.fn();
+    feedService.build = jest.fn();
   });
 
   it('should build pages ordered by descending date', () => {
@@ -72,4 +74,22 @@ describe('Homepage Service', () => {
     homepageService.build([first, second], outputDirectory);
     expect(fileService.write).not.toHaveBeenCalledWith(`${outputDirectory}/l/en-US/index.html`, expect.any(String));
   });
+
+  it('should write an atom feed file', () => {
+    stubPageBuild();
+    const [first] = postsMock;
+    homepageService.build([first], '');
+    expect(feedService.build).toHaveBeenCalledWith([first], undefined);
+    expect(feedService.build).toHaveBeenCalledTimes(1);
+  });
+
+  it('should write language-specific atom feed files if posts have been written in more than one language', () => {
+    stubPageBuild();
+    const [first, second, third] = postsMock;
+    homepageService.build(postsMock, '');
+    expect(feedService.build).toHaveBeenCalledWith([second, third, first], undefined);
+    expect(feedService.build).toHaveBeenCalledWith([second, first], 'en-US');
+    expect(feedService.build).toHaveBeenCalledWith([third], 'pt-BR');
+    expect(feedService.build).toHaveBeenCalledTimes(3);
+  });
 });