feat: add ability to create a File object from URL (#2432)

* feat: add ability to create a File object from URL

* fixes

* linter fixes

src/file.ts

@@ -479,6 +479,9 @@ export class RequestError extends Error {
 }
 
 const SEVEN_DAYS = 7 * 24 * 60 * 60;
+const GS_UTIL_URL_REGEX = /(gs):\/\/([a-z0-9_.-]+)\/(.+)/g;
+const HTTPS_PUBLIC_URL_REGEX =
+  /(https):\/\/(storage\.googleapis\.com)\/([a-z0-9_.-]+)\/(.+)/g;
 
 export enum FileExceptionMessages {
   EXPIRATION_TIME_NA = 'An expiration time is not available.',
@@ -2358,6 +2361,35 @@ class File extends ServiceObject<File, FileMetadata> {
     return this;
   }
 
+  /**
+   * Gets a reference to a Cloud Storage {@link File} file from the provided URL in string format.
+   * @param {string} publicUrlOrGsUrl the URL as a string. Must be of the format gs://bucket/file
+   *  or https://storage.googleapis.com/bucket/file.
+   * @param {Storage} storageInstance an instance of a Storage object.
+   * @param {FileOptions} [options] Configuration options
+   * @returns {File}
+   */
+  static from(
+    publicUrlOrGsUrl: string,
+    storageInstance: Storage,
+    options?: FileOptions
+  ): File {
+    const gsMatches = [...publicUrlOrGsUrl.matchAll(GS_UTIL_URL_REGEX)];
+    const httpsMatches = [...publicUrlOrGsUrl.matchAll(HTTPS_PUBLIC_URL_REGEX)];
+
+    if (gsMatches.length > 0) {
+      const bucket = new Bucket(storageInstance, gsMatches[0][1]);
+      return new File(bucket, gsMatches[0][2], options);
+    } else if (httpsMatches.length > 0) {
+      const bucket = new Bucket(storageInstance, httpsMatches[0][2]);
+      return new File(bucket, httpsMatches[0][3], options);
+    } else {
+      throw new Error(
+        'URL string must be of format gs://bucket/file or https://storage.googleapis.com/bucket/file'
+      );
+    }
+  }
+
   get(options?: GetFileOptions): Promise<GetResponse<File>>;
   get(callback: InstanceResponseCallback<File>): void;
   get(options: GetFileOptions, callback: InstanceResponseCallback<File>): void;

test/file.ts

@@ -5168,4 +5168,49 @@ describe('File', () => {
       file.setUserProject(userProject);
     });
   });
+
+  describe('from', () => {
+    it('should create a File object from a gs:// formatted URL', () => {
+      const gsUrl = 'gs://mybucket/myfile';
+      const result = File.from(gsUrl, STORAGE);
+
+      assert(result);
+      assert(result.bucket.name, 'mybucket');
+      assert(result.name, 'myfile');
+    });
+
+    it('should create a File object from a gs:// formatted URL including a folder', () => {
+      const gsUrl = 'gs://mybucket/myfolder/myfile';
+      const result = File.from(gsUrl, STORAGE);
+
+      assert(result);
+      assert(result.bucket.name, 'mybucket');
+      assert(result.name, 'myfolder/myfile');
+    });
+
+    it('should create a File object from a https:// formatted URL', () => {
+      const httpsUrl = 'https://storage.googleapis.com/mybucket/myfile';
+      const result = File.from(httpsUrl, STORAGE);
+
+      assert(result);
+      assert(result.bucket.name, 'mybucket');
+      assert(result.name, 'myfile');
+    });
+
+    it('should create a File object from a https:// formatted URL including a folder', () => {
+      const httpsUrl =
+        'https://storage.googleapis.com/mybucket/myfolder/myfile';
+      const result = File.from(httpsUrl, STORAGE);
+
+      assert(result);
+      assert(result.bucket.name, 'mybucket');
+      assert(result.name, 'myfolder/myfile');
+    });
+
+    it('should throw an error when invoked with an incorrectly formatted URL', () => {
+      const invalidUrl = 'https://storage.com/mybucket/myfile';
+
+      assert.throws(() => File.from(invalidUrl, STORAGE));
+    });
+  });
 });