package test;

import com.google.auth.oauth2.GoogleCredentials;
import com.google.cloud.ReadChannel;
import com.google.cloud.storage.BlobId;
import com.google.cloud.storage.StorageOptions;
import org.testng.annotations.Test;
import org.testng.collections.Lists;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;

public class test {
    @Test
    public void testDownload() throws Exception {
        GoogleCredentials credentials = GoogleCredentials.fromStream(new FileInputStream("/path/secret.json"))
                .createScoped(Lists.newArrayList("https://www.googleapis.com/auth/cloud-platform"));
        var storage = StorageOptions.newBuilder().setCredentials(credentials).build().getService();

        var bucket = "test-bucket";
        var name = "test.file";

        var blobReference = new GCPRemoteObjectReference(BlobId.of(bucket, name));

        final File localFilePath = Paths.get("/local/path/test.file").toFile();

        try (final ReadChannel inputChannel = storage.reader(blobReference.getBlobId())) {
            localFilePath.getParentFile().mkdirs();
            try (FileChannel fileChannel = new FileOutputStream(localFilePath).getChannel()) {
                ByteBuffer bytes = ByteBuffer.allocate(64 * 1024);

                while (inputChannel.read(bytes) > 0) {
                    ((Buffer) bytes).flip();
                    fileChannel.write(bytes);
                    bytes.clear();
                }
            }
        }
    }

}