feat: add ability to download repository content as zip/tar (#152)

* separate methods to download the tar or zip archive
* methods return an Optional InputStream that can be consumed

src/main/java/com/spotify/github/v3/clients/RepositoryClient.java

@@ -50,6 +50,7 @@
 import com.spotify.github.v3.repos.Status;
 import com.spotify.github.v3.repos.requests.AuthenticatedUserRepositoriesFilter;
 import com.spotify.github.v3.repos.requests.RepositoryCreateStatus;
+import java.io.InputStream;
 import java.lang.invoke.MethodHandles;
 import java.util.Iterator;
 import java.util.List;
@@ -91,6 +92,8 @@ public class RepositoryClient {
   private static final String REPOSITORY_COLLABORATOR = "/repos/%s/%s/collaborators/%s";
   private static final String REPOSITORY_INVITATION = "/repos/%s/%s/invitations/%s";
   private static final String REPOSITORY_INVITATIONS = "/repos/%s/%s/invitations";
+  private static final String REPOSITORY_DOWNLOAD_TARBALL = "/repos/%s/%s/tarball/%s";
+  private static final String REPOSITORY_DOWNLOAD_ZIPBALL = "/repos/%s/%s/zipball/%s";
   private final String owner;
   private final String repo;
   private final GitHubClient github;
@@ -242,6 +245,56 @@ public CompletableFuture<List<RepositoryInvitation>> listInvitations() {
     return github.request(path, LIST_REPOSITORY_INVITATION);
   }
 
+  /**
+   * Downloads a tar archive of the repository’s default branch (usually main).
+   *
+   * @return a CompletableFuture that resolves to an Optional InputStream
+   */
+  public CompletableFuture<Optional<InputStream>> downloadTarball() {
+    return downloadRepository(REPOSITORY_DOWNLOAD_TARBALL, Optional.empty());
+  }
+
+  /**
+   * Downloads a tar archive of the repository. Use :ref to specify a branch or tag to download.
+   *
+   * @return a CompletableFuture that resolves to an Optional InputStream
+   */
+  public CompletableFuture<Optional<InputStream>> downloadTarball(final String ref) {
+    return downloadRepository(REPOSITORY_DOWNLOAD_TARBALL, Optional.of(ref));
+  }
+
+  /**
+   * Downloads a zip archive of the repository’s default branch (usually main).
+   *
+   * @return a CompletableFuture that resolves to an Optional InputStream
+   */
+  public CompletableFuture<Optional<InputStream>> downloadZipball() {
+    return downloadRepository(REPOSITORY_DOWNLOAD_ZIPBALL, Optional.empty());
+  }
+
+  /**
+   * Downloads a zip archive of the repository. Use :ref to specify a branch or tag to download.
+   *
+   * @return a CompletableFuture that resolves to an Optional InputStream
+   */
+  public CompletableFuture<Optional<InputStream>> downloadZipball(final String ref) {
+    return downloadRepository(REPOSITORY_DOWNLOAD_ZIPBALL, Optional.of(ref));
+  }
+
+  private CompletableFuture<Optional<InputStream>> downloadRepository(final String path, final Optional<String> maybeRef) {
+    final var repoRef = maybeRef.orElse("");
+    final var repoPath = String.format(path, owner, repo, repoRef);
+    return github.request(repoPath).thenApply(response -> {
+      var body = response.body();
+
+      if (body == null) {
+        return Optional.empty();
+      }
+
+      return Optional.of(body.byteStream());
+    });
+  }
+
   /**
    * Create a webhook.
    *

src/test/java/com/spotify/github/v3/clients/RepositoryClientTest.java

@@ -65,6 +65,8 @@
 import com.spotify.github.v3.repos.Status;
 import com.spotify.github.v3.repos.requests.ImmutableAuthenticatedUserRepositoriesFilter;
 import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
@@ -537,4 +539,63 @@ public void mergeNoop() {
     final Optional<CommitItem> maybeCommit = repoClient.merge("basebranch", "headbranch").join();
     assertThat(maybeCommit, is(Optional.empty()));
   }
+
+  @Test
+  public void shouldDownloadTarball() throws Exception {
+    CompletableFuture<Response> fixture = completedFuture(
+        new Response.Builder()
+            .request(new Request.Builder().url("https://example.com/whatever").build())
+            .protocol(Protocol.HTTP_1_1)
+            .message("")
+            .code(200)
+            .body(
+                ResponseBody.create(
+                    "some bytes".getBytes(StandardCharsets.UTF_8),
+                    MediaType.get("application/gzip")
+                ))
+            .build());
+    when(github.request("/repos/someowner/somerepo/tarball/")).thenReturn(fixture);
+
+    try(InputStream response = repoClient.downloadTarball().get().orElseThrow()) {
+      String result = new String(response.readAllBytes(), StandardCharsets.UTF_8);
+      assertThat(result, is("some bytes"));
+    }
+  }
+
+  @Test
+  public void shouldDownloadZipball() throws Exception {
+    CompletableFuture<Response> fixture = completedFuture(
+        new Response.Builder()
+            .request(new Request.Builder().url("https://example.com/whatever").build())
+            .protocol(Protocol.HTTP_1_1)
+            .message("")
+            .code(200)
+            .body(
+                ResponseBody.create(
+                    "some bytes".getBytes(StandardCharsets.UTF_8),
+                    MediaType.get("application/gzip")
+                ))
+            .build());
+    when(github.request("/repos/someowner/somerepo/zipball/")).thenReturn(fixture);
+
+    try (InputStream response = repoClient.downloadZipball().get().orElseThrow()) {
+      String result = new String(response.readAllBytes(), StandardCharsets.UTF_8);
+      assertThat(result, is("some bytes"));
+    }
+  }
+
+  @Test
+  public void shouldReturnEmptyOptionalWhenResponseBodyNotPresent() throws Exception {
+    CompletableFuture<Response> fixture = completedFuture(
+        new Response.Builder()
+            .request(new Request.Builder().url("https://example.com/whatever").build())
+            .protocol(Protocol.HTTP_1_1)
+            .message("")
+            .code(204) // No Content
+            .build());
+    when(github.request("/repos/someowner/somerepo/zipball/master")).thenReturn(fixture);
+
+    Optional<InputStream> response = repoClient.downloadZipball("master").get();
+    assertThat(response, is(Optional.empty()));
+  }
 }