ci(docs-infra): change AIO preview server stuff to pull builds from CircleCI

Previously, Travis pushed the build artitfacts to the preview server.
This required us to use JWT to secure the POST request from Travis, to
ensure we couldn't receive malicious builds.

JWT has been deprecated and we are moving our builds to CircleCI.

This commit rewrites the TypeScript part of the preview server that
handles converting build artifact into hosted previews of the docs.

aio/aio-builds-setup/dockerbuild/scripts-js/test/common/utils.spec.ts

@@ -1,9 +1,53 @@
 // Imports
-import {assertNotMissingOrEmpty, getEnvVar} from '../../lib/common/utils';
+import {
+  assert,
+  assertNotMissingOrEmpty,
+  computeArtifactDownloadPath,
+  computeShortSha,
+  getEnvVar,
+  getPrInfoFromDownloadPath,
+} from '../../lib/common/utils';
 
 // Tests
 describe('utils', () => {
 
+  describe('computeShortSha', () => {
+    it('should return only the first SHORT_SHA_LEN characters of the SHA', () => {
+      expect(computeShortSha('0123456789')).toEqual('0123456');
+      expect(computeShortSha('ABC')).toEqual('ABC');
+      expect(computeShortSha('')).toEqual('');
+    });
+  });
+
+  describe('assert', () => {
+    it('should throw if passed a false value', () => {
+      expect(() => assert(false, 'error message')).toThrowError('error message');
+    });
+
+    it('should not throw if passed a true value', () => {
+      expect(() => assert(true, 'error message')).not.toThrow();
+    });
+  });
+
+  describe('computeArtifactDownloadPath', () => {
+    it('should compute an absolute path based on the artifact info provided', () => {
+      const downloadDir = '/a/b/c';
+      const pr = 123;
+      const sha = 'ABCDEF1234567';
+      const artifactPath = 'a/path/to/file.zip';
+      const path = computeArtifactDownloadPath(downloadDir, pr, sha, artifactPath);
+      expect(path).toEqual('/a/b/c/123-ABCDEF1-file.zip');
+    });
+  });
+
+  describe('getPrInfoFromDownloadPath', () => {
+    it('should extract the PR and SHA from the file path', () => {
+      const {pr, sha} = getPrInfoFromDownloadPath('a/b/c/12345-ABCDE-artifact.zip');
+      expect(pr).toEqual(12345);
+      expect(sha).toEqual('ABCDE');
+    });
+  });
+
   describe('assertNotMissingOrEmpty()', () => {
 
     it('should throw if passed an empty value', () => {