/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.beam.runners.fnexecution.state;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.assertThat;
import static org.mockito.Matchers.any;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;

import java.nio.charset.StandardCharsets;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.TimeUnit;
import org.apache.beam.model.fnexecution.v1.BeamFnApi;
import org.apache.beam.sdk.fn.test.TestStreams;
import org.apache.beam.vendor.grpc.v1.io.grpc.stub.StreamObserver;
import org.apache.beam.vendor.protobuf.v3.com.google.protobuf.ByteString;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.MockitoAnnotations;

/** Tests for {@link org.apache.beam.runners.fnexecution.state.GrpcStateService}. */
@RunWith(JUnit4.class)
public class GrpcStateServiceTest {
  private static final long TIMEOUT_MS = 30 * 1000;

  private GrpcStateService stateService;

  @Mock private StreamObserver<BeamFnApi.StateResponse> responseObserver;

  @Mock private StateRequestHandler handler;

  @Before
  public void setUp() throws Exception {
    MockitoAnnotations.initMocks(this);
    stateService = GrpcStateService.create();
  }

  /**
   * After a handler has been registered with {@link
   * GrpcStateService#registerForProcessBundleInstructionId(String, StateRequestHandler)}, the
   * {@link GrpcStateService} should delegate requests through {@link
   * GrpcStateService#state(StreamObserver)} to the registered handler.
   */
  @Test
  public void testStateRequestsHandledByRegisteredHandlers() throws Exception {
    // register handler
    String bundleInstructionId = "bundle_instruction";
    stateService.registerForProcessBundleInstructionId(bundleInstructionId, handler);

    // open state stream
    StreamObserver requestObserver = stateService.state(responseObserver);

    // send state request
    BeamFnApi.StateRequest request =
        BeamFnApi.StateRequest.newBuilder().setInstructionReference(bundleInstructionId).build();
    requestObserver.onNext(request);

    // assert behavior
    verify(handler).handle(request);
  }

  @Test
  public void testHandlerResponseSentToStateStream() throws Exception {
    // define handler behavior
    ByteString expectedResponseData =
        ByteString.copyFrom("EXPECTED_RESPONSE_DATA", StandardCharsets.UTF_8);
    String bundleInstructionId = "EXPECTED_BUNDLE_INSTRUCTION_ID";
    BeamFnApi.StateResponse.Builder expectedBuilder =
        BeamFnApi.StateResponse.newBuilder()
            .setGet(BeamFnApi.StateGetResponse.newBuilder().setData(expectedResponseData));
    StateRequestHandler dummyHandler =
        (request) -> {
          CompletableFuture<BeamFnApi.StateResponse.Builder> response = new CompletableFuture<>();
          response.complete(expectedBuilder);
          return response;
        };

    // define observer behavior
    BlockingDeque<BeamFnApi.StateResponse> responses = new LinkedBlockingDeque<>();
    StreamObserver<BeamFnApi.StateResponse> recordingResponseObserver =
        TestStreams.withOnNext(responses::add).build();
    recordingResponseObserver = Mockito.spy(recordingResponseObserver);

    // register handler
    stateService.registerForProcessBundleInstructionId(bundleInstructionId, dummyHandler);

    // open state stream
    StreamObserver<BeamFnApi.StateRequest> requestObserver =
        stateService.state(recordingResponseObserver);

    // send state request
    BeamFnApi.StateRequest request =
        BeamFnApi.StateRequest.newBuilder().setInstructionReference(bundleInstructionId).build();
    requestObserver.onNext(request);

    // wait for response
    BeamFnApi.StateResponse response = responses.poll(TIMEOUT_MS, TimeUnit.MILLISECONDS);

    // assert that responses contain a built state response
    verify(recordingResponseObserver, times(1)).onNext(any());
    verify(recordingResponseObserver, never()).onCompleted();
    verify(recordingResponseObserver, never()).onError(any());
    assertThat(response.getGet().getData(), equalTo(expectedResponseData));
  }
}
