/*
 * Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.storage.object;

// [START storage_list_files_with_prefix]
import com.google.api.gax.paging.Page;
import com.google.cloud.storage.Blob;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

public class ListObjectsWithPrefix {
  public static void listObjectsWithPrefix(
      String projectId, String bucketName, String directoryPrefix) {
    // The ID of your GCP project
    // String projectId = "your-project-id";

    // The ID of your GCS bucket
    // String bucketName = "your-unique-bucket-name";

    // The directory prefix to search for
    // String directoryPrefix = "myDirectory/"

    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();
    /**
     * Using the Storage.BlobListOption.currentDirectory() option here causes the results to display
     * in a "directory-like" mode, showing what objects are in the directory you've specified, as
     * well as what other directories exist in that directory. For example, given these blobs:
     *
     * <p>a/1.txt a/b/2.txt a/b/3.txt
     *
     * <p>If you specify prefix = "a/" and don't use Storage.BlobListOption.currentDirectory(),
     * you'll get back:
     *
     * <p>a/1.txt a/b/2.txt a/b/3.txt
     *
     * <p>However, if you specify prefix = "a/" and do use
     * Storage.BlobListOption.currentDirectory(), you'll get back:
     *
     * <p>a/1.txt a/b/
     *
     * <p>Because a/1.txt is the only file in the a/ directory and a/b/ is a directory inside the
     * /a/ directory.
     */
    Page<Blob> blobs =
        storage.list(
            bucketName,
            Storage.BlobListOption.prefix(directoryPrefix),
            Storage.BlobListOption.currentDirectory());

    for (Blob blob : blobs.iterateAll()) {
      System.out.println(blob.getName());
    }
  }
}
// [END storage_list_files_with_prefix]
