feat: Add from and to storage url options for BlobId (#888)

* Add from and to storage url options for BlobId

* Better name

Author: JesseLovelace

google-cloud-storage/src/main/java/com/google/cloud/storage/BlobId.java

@@ -22,6 +22,7 @@
 import com.google.common.base.MoreObjects;
 import java.io.Serializable;
 import java.util.Objects;
+import java.util.regex.Pattern;
 
 /**
  * Google Storage Object identifier. A {@code BlobId} object includes the name of the containing
@@ -56,6 +57,11 @@ public Long getGeneration() {
     return generation;
   }
 
+  /** Returns this blob's Storage url which can be used with gsutil */
+  public String toGsUtilUri() {
+    return "gs://" + bucket + "/" + name;
+  }
+
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this)
@@ -114,6 +120,23 @@ public static BlobId of(String bucket, String name, Long generation) {
     return new BlobId(checkNotNull(bucket), checkNotNull(name), generation);
   }
 
+  /**
+   * Creates a {@code BlobId} object.
+   *
+   * @param gsUtilUri the Storage url to create the blob from
+   */
+  public static BlobId fromGsUtilUri(String gsUtilUri) {
+    if (!Pattern.matches("gs://.*/.*", gsUtilUri)) {
+      throw new IllegalArgumentException(
+          gsUtilUri + " is not a valid gsutil URI (i.e. \"gs://bucket/blob\")");
+    }
+    int blobNameStartIndex = gsUtilUri.indexOf('/', 5);
+    String bucketName = gsUtilUri.substring(5, blobNameStartIndex);
+    String blobName = gsUtilUri.substring(blobNameStartIndex + 1);
+
+    return BlobId.of(bucketName, blobName);
+  }
+
   static BlobId fromPb(StorageObject storageObject) {
     return BlobId.of(
         storageObject.getBucket(), storageObject.getName(), storageObject.getGeneration());

google-cloud-storage/src/test/java/com/google/cloud/storage/BlobIdTest.java

@@ -31,6 +31,14 @@ public void testOf() {
     assertEquals("n", blobId.getName());
   }
 
+  @Test
+  public void testToFromGsUtilUri() {
+    BlobId blobId = BlobId.fromGsUtilUri("gs://bucket/path/to/blob");
+    assertEquals("bucket", blobId.getBucket());
+    assertEquals("path/to/blob", blobId.getName());
+    assertEquals("gs://bucket/path/to/blob", blobId.toGsUtilUri());
+  }
+
   @Test
   public void testEquals() {
     compareBlobIds(BLOB, BlobId.of("b", "n"));