[samplecode]Implement class header method sample code

src/main/java/com/google/api/generator/gapic/composer/ServiceClientClassComposer.java

@@ -129,7 +129,8 @@ public GapicClass generate(
 
     ClassDefinition classDef =
         ClassDefinition.builder()
-            .setHeaderCommentStatements(createClassHeaderComments(service, typeStore))
+            .setHeaderCommentStatements(
+                createClassHeaderComments(service, typeStore, resourceNames, messageTypes))
             .setPackageString(pakkage)
             .setAnnotations(createClassAnnotations(pakkage, typeStore))
             .setScope(ScopeNode.PUBLIC)
@@ -161,17 +162,23 @@ private static List<TypeNode> createClassImplements(TypeStore typeStore) {
   }
 
   private static List<CommentStatement> createClassHeaderComments(
-      Service service, TypeStore typeStore) {
+      Service service,
+      TypeStore typeStore,
+      Map<String, ResourceName> resourceNames,
+      Map<String, Message> messageTypes) {
     TypeNode clientType = typeStore.get(ClassNames.getServiceClientClassName(service));
     TypeNode settingsType = typeStore.get(ClassNames.getServiceSettingsClassName(service));
+    String classMethodSampleCode =
+        ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(
+            service, clientType, resourceNames, messageTypes);
     String credentialsSampleCode =
         ServiceClientSampleCodeComposer.composeClassHeaderCredentialsSampleCode(
             clientType, settingsType);
     String endpointSampleCode =
         ServiceClientSampleCodeComposer.composeClassHeaderEndpointSampleCode(
             clientType, settingsType);
     return ServiceClientCommentComposer.createClassHeaderComments(
-        service, credentialsSampleCode, endpointSampleCode);
+        service, classMethodSampleCode, credentialsSampleCode, endpointSampleCode);
   }
 
   private static List<MethodDefinition> createClassMethods(

src/main/java/com/google/api/generator/gapic/composer/comment/ServiceClientCommentComposer.java

@@ -110,7 +110,10 @@ public class ServiceClientCommentComposer {
               + " operation returned by another API method call.");
 
   public static List<CommentStatement> createClassHeaderComments(
-      Service service, String credentialsSampleCode, String endpointSampleCode) {
+      Service service,
+      String classMethodSampleCode,
+      String credentialsSampleCode,
+      String endpointSampleCode) {
     JavaDocComment.Builder classHeaderJavadocBuilder = JavaDocComment.builder();
     if (service.hasDescription()) {
       classHeaderJavadocBuilder =
@@ -122,7 +125,7 @@ public static List<CommentStatement> createClassHeaderComments(
 
     // Service introduction.
     classHeaderJavadocBuilder.addParagraph(SERVICE_DESCRIPTION_INTRO_STRING);
-    // TODO(summerji): Add sample code here.
+    classHeaderJavadocBuilder.addSampleCode(classMethodSampleCode);
 
     // API surface description.
     classHeaderJavadocBuilder.addParagraph(

src/main/java/com/google/api/generator/gapic/composer/samplecode/ServiceClientSampleCodeComposer.java

@@ -50,6 +50,7 @@
 import com.google.api.generator.gapic.model.Method.Stream;
 import com.google.api.generator.gapic.model.MethodArgument;
 import com.google.api.generator.gapic.model.ResourceName;
+import com.google.api.generator.gapic.model.Service;
 import com.google.api.generator.gapic.utils.JavaStyle;
 import com.google.common.base.Preconditions;
 import com.google.common.base.Strings;
@@ -64,6 +65,30 @@
 
 public class ServiceClientSampleCodeComposer {
 
+  public static String composeClassHeaderMethodSampleCode(
+      Service service,
+      TypeNode clientType,
+      Map<String, ResourceName> resourceNames,
+      Map<String, Message> messageTypes) {
+    // Use the first pure unary RPC method's sample code as showcase, if no such method exists, use
+    // the first method in the service's methods list.
+    Method method =
+        service.methods().stream()
+            .filter(m -> m.stream() == Stream.NONE && !m.hasLro() && !m.isPaged())
+            .findFirst()
+            .orElse(service.methods().get(0));
+    if (method.stream() == Stream.NONE) {
+      if (method.methodSignatures().isEmpty()) {
+        return composeRpcDefaultMethodHeaderSampleCode(
+            method, clientType, resourceNames, messageTypes);
+      }
+      return composeRpcMethodHeaderSampleCode(
+          method, clientType, method.methodSignatures().get(0), resourceNames, messageTypes);
+    }
+    return composeStreamCallableMethodHeaderSampleCode(
+        method, clientType, resourceNames, messageTypes);
+  }
+
   public static String composeClassHeaderCredentialsSampleCode(
       TypeNode clientType, TypeNode settingsType) {
     // Initialize clientSettings with builder() method.

src/test/java/com/google/api/generator/gapic/composer/goldens/EchoClient.golden

@@ -34,6 +34,12 @@ import javax.annotation.Generated;
  * This class provides the ability to make remote calls to the backing service through method calls
  * that map to API methods. Sample code to get started:
  *
+ * <pre>{@code
+ * try (EchoClient echoClient = EchoClient.create()) {
+ *   EchoResponse response = echoClient.echo();
+ * }
+ * }</pre>
+ *
  * <p>Note: close() needs to be called on the EchoClient object to clean up resources such as
  * threads. In the example above, try-with-resources is used, which automatically calls close().
  *

src/test/java/com/google/api/generator/gapic/composer/goldens/IdentityClient.golden

@@ -24,6 +24,15 @@ import javax.annotation.Generated;
  * This class provides the ability to make remote calls to the backing service through method calls
  * that map to API methods. Sample code to get started:
  *
+ * <pre>{@code
+ * try (IdentityClient identityClient = IdentityClient.create()) {
+ *   String parent = UserName.of("[USER]").toString();
+ *   String displayName = "displayName1714148973";
+ *   String email = "email96619420";
+ *   User response = identityClient.createUser(parent, displayName, email);
+ * }
+ * }</pre>
+ *
  * <p>Note: close() needs to be called on the IdentityClient object to clean up resources such as
  * threads. In the example above, try-with-resources is used, which automatically calls close().
  *

src/test/java/com/google/api/generator/gapic/composer/samplecode/ServiceClientSampleCodeComposerTest.java

@@ -30,14 +30,19 @@
 import com.google.api.generator.gapic.model.MethodArgument;
 import com.google.api.generator.gapic.model.ResourceName;
 import com.google.api.generator.gapic.model.ResourceReference;
+import com.google.api.generator.gapic.model.Service;
 import com.google.api.generator.gapic.protoparser.Parser;
 import com.google.api.generator.testutils.LineFormatter;
 import com.google.protobuf.Descriptors.FileDescriptor;
+import com.google.protobuf.Descriptors.ServiceDescriptor;
 import com.google.showcase.v1beta1.EchoOuterClass;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
 import org.junit.Test;
 
 public class ServiceClientSampleCodeComposerTest {
@@ -46,6 +51,218 @@ public class ServiceClientSampleCodeComposerTest {
   private static final String PROTO_PACKAGE_NAME = "com.google.protobuf";
 
   // =============================== Class Header Sample Code ===============================//
+  @Test
+  public void composeClassHeaderMethodSampleCode_unaryRpc() {
+    FileDescriptor echoFileDescriptor = EchoOuterClass.getDescriptor();
+    Map<String, ResourceName> resourceNames = Parser.parseResourceNames(echoFileDescriptor);
+    Map<String, Message> messageTypes = Parser.parseMessages(echoFileDescriptor);
+    ServiceDescriptor echoService = echoFileDescriptor.getServices().get(0);
+    Set<ResourceName> outputResourceNames = new HashSet<>();
+    List<Service> services =
+        Parser.parseService(
+            echoFileDescriptor, messageTypes, resourceNames, Optional.empty(), outputResourceNames);
+    Service echoProtoService = services.get(0);
+    TypeNode clientType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoClient")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    String results = ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(echoProtoService, clientType, resourceNames, messageTypes);
+    String expected =
+        LineFormatter.lines(
+            "try (EchoClient echoClient = EchoClient.create()) {\n",
+            "  EchoResponse response = echoClient.echo();\n",
+            "}");
+    assertEquals(expected, results);
+  }
+
+  @Test
+  public void composeClassHeaderMethodSampleCode_firstMethodIsNotUnaryRpc() {
+    FileDescriptor echoFileDescriptor = EchoOuterClass.getDescriptor();
+    Map<String, ResourceName> resourceNames = Parser.parseResourceNames(echoFileDescriptor);
+    Map<String, Message> messageTypes = Parser.parseMessages(echoFileDescriptor);
+    TypeNode inputType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("WaitRequest")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    TypeNode outputType =
+        TypeNode.withReference(
+            VaporReference.builder().setName("Operation").setPakkage(LRO_PACKAGE_NAME).build());
+    TypeNode responseType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("WaitResponse")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    TypeNode metadataType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("WaitMetadata")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    LongrunningOperation lro = LongrunningOperation.withTypes(responseType, metadataType);
+    TypeNode ttlTypeNode =
+        TypeNode.withReference(
+            VaporReference.builder().setName("Duration").setPakkage(PROTO_PACKAGE_NAME).build());
+    MethodArgument ttl =
+        MethodArgument.builder()
+            .setName("ttl")
+            .setType(ttlTypeNode)
+            .setField(
+                Field.builder()
+                    .setName("ttl")
+                    .setType(ttlTypeNode)
+                    .setIsMessage(true)
+                    .setIsContainedInOneof(true)
+                    .build())
+            .build();
+    Method method =
+        Method.builder()
+            .setName("Wait")
+            .setInputType(inputType)
+            .setOutputType(outputType)
+            .setLro(lro)
+            .setMethodSignatures(Arrays.asList(Arrays.asList(ttl)))
+            .build();
+    Service service = Service.builder()
+        .setName("Echo")
+        .setDefaultHost("localhost:7469")
+        .setOauthScopes(Arrays.asList("https://www.googleapis.com/auth/cloud-platform"))
+        .setPakkage(SHOWCASE_PACKAGE_NAME)
+        .setProtoPakkage(SHOWCASE_PACKAGE_NAME)
+        .setOriginalJavaPackage(SHOWCASE_PACKAGE_NAME)
+        .setOverriddenName("Echo")
+        .setMethods(Arrays.asList(method))
+        .build();
+    TypeNode clientType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoClient")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    String results =
+        ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(
+            service, clientType, resourceNames, messageTypes);
+    String expected =
+        LineFormatter.lines(
+            "try (EchoClient echoClient = EchoClient.create()) {\n",
+            "  Duration ttl = Duration.newBuilder().build();\n",
+            "  WaitResponse response = echoClient.waitAsync(ttl).get();\n",
+            "}");
+    assertEquals(results, expected);
+  }
+
+  @Test
+  public void composeClassHeaderMethodSampleCode_firstMethodHasNoSignatures() {
+    FileDescriptor echoFileDescriptor = EchoOuterClass.getDescriptor();
+    Map<String, ResourceName> resourceNames = Parser.parseResourceNames(echoFileDescriptor);
+    Map<String, Message> messageTypes = Parser.parseMessages(echoFileDescriptor);
+    TypeNode inputType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoRequest")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    TypeNode outputType =
+        TypeNode.withReference(
+            VaporReference.builder().setName("EchoResponse").setPakkage(SHOWCASE_PACKAGE_NAME).build());
+    Method method =
+        Method.builder()
+            .setName("Echo")
+            .setInputType(inputType)
+            .setOutputType(outputType)
+            .setMethodSignatures(Collections.emptyList())
+            .build();
+    Service service = Service.builder()
+        .setName("Echo")
+        .setDefaultHost("localhost:7469")
+        .setOauthScopes(Arrays.asList("https://www.googleapis.com/auth/cloud-platform"))
+        .setPakkage(SHOWCASE_PACKAGE_NAME)
+        .setProtoPakkage(SHOWCASE_PACKAGE_NAME)
+        .setOriginalJavaPackage(SHOWCASE_PACKAGE_NAME)
+        .setOverriddenName("Echo")
+        .setMethods(Arrays.asList(method))
+        .build();
+    TypeNode clientType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoClient")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    String results =
+        ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(
+            service, clientType, resourceNames, messageTypes);
+    String expected =
+        LineFormatter.lines(
+            "try (EchoClient echoClient = EchoClient.create()) {\n",
+            "  EchoRequest request =\n",
+            "      EchoRequest.newBuilder()\n",
+            "          .setName(FoobarName.ofProjectFoobarName(\"[PROJECT]\", \"[FOOBAR]\").toString())\n",
+            "          .setParent(FoobarName.ofProjectFoobarName(\"[PROJECT]\", \"[FOOBAR]\").toString())\n",
+            "          .setFoobar(Foobar.newBuilder().build())\n",
+            "          .build();\n",
+            "  EchoResponse response = echoClient.echo(request);\n",
+            "}");
+    assertEquals(results, expected);
+  }
+
+  @Test
+  public void composeClassHeaderMethodSampleCode_firstMethodIsStream() {
+    FileDescriptor echoFileDescriptor = EchoOuterClass.getDescriptor();
+    Map<String, ResourceName> resourceNames = Parser.parseResourceNames(echoFileDescriptor);
+    Map<String, Message> messageTypes = Parser.parseMessages(echoFileDescriptor);
+    TypeNode inputType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("ExpandRequest")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    TypeNode outputType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoResponse")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    Method method =
+        Method.builder()
+            .setName("Expand")
+            .setInputType(inputType)
+            .setOutputType(outputType)
+            .setStream(Stream.SERVER)
+            .build();
+    Service service = Service.builder()
+        .setName("Echo")
+        .setDefaultHost("localhost:7469")
+        .setOauthScopes(Arrays.asList("https://www.googleapis.com/auth/cloud-platform"))
+        .setPakkage(SHOWCASE_PACKAGE_NAME)
+        .setProtoPakkage(SHOWCASE_PACKAGE_NAME)
+        .setOriginalJavaPackage(SHOWCASE_PACKAGE_NAME)
+        .setOverriddenName("Echo")
+        .setMethods(Arrays.asList(method))
+        .build();
+    TypeNode clientType =
+        TypeNode.withReference(
+            VaporReference.builder()
+                .setName("EchoClient")
+                .setPakkage(SHOWCASE_PACKAGE_NAME)
+                .build());
+    String results = ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(service, clientType, resourceNames, messageTypes);
+    String expected =
+        LineFormatter.lines(
+            "try (EchoClient echoClient = EchoClient.create()) {\n",
+            "  ExpandRequest request =\n",
+            "      ExpandRequest.newBuilder().setContent(\"content951530617\").setInfo(\"info3237038\").build();\n",
+            "  ServerStream<EchoResponse> stream = echoClient.expandCallable().call(request);\n",
+            "  for (EchoResponse response : stream) {\n",
+            "    // Do something when a response is received.\n",
+            "  }\n",
+            "}");
+    assertEquals(results, expected);
+  }
+
   @Test
   public void composeClassHeaderCredentialsSampleCode() {
     TypeNode clientType =

test/integration/goldens/asset/AssetServiceClient.java

@@ -46,6 +46,18 @@
  * <p>This class provides the ability to make remote calls to the backing service through method
  * calls that map to API methods. Sample code to get started:
  *
+ * <pre>{@code
+ * try (AssetServiceClient assetServiceClient = AssetServiceClient.create()) {
+ *   BatchGetAssetsHistoryRequest request =
+ *       BatchGetAssetsHistoryRequest.newBuilder()
+ *           .setParent(FeedName.ofProjectFeedName("[PROJECT]", "[FEED]").toString())
+ *           .addAllAssetNames(new ArrayList<String>())
+ *           .setReadTimeWindow(TimeWindow.newBuilder().build())
+ *           .build();
+ *   BatchGetAssetsHistoryResponse response = assetServiceClient.batchGetAssetsHistory(request);
+ * }
+ * }</pre>
+ *
  * <p>Note: close() needs to be called on the AssetServiceClient object to clean up resources such
  * as threads. In the example above, try-with-resources is used, which automatically calls close().
  *