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   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
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   *
   *     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,
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   * See the License for the specific language governing permissions and
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  package org.apache.cassandra.sidecar.client.retry;
  
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.CompletionException;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.params.ParameterizedTest;
  import org.junit.jupiter.params.provider.ValueSource;
  
  import org.apache.cassandra.sidecar.client.HttpResponse;
  import org.apache.cassandra.sidecar.client.exception.RetriesExhaustedException;
  import org.apache.cassandra.sidecar.common.request.Request;
  
  import static io.netty.handler.codec.http.HttpResponseStatus.INTERNAL_SERVER_ERROR;
  import static io.netty.handler.codec.http.HttpResponseStatus.OK;
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  import static org.assertj.core.api.Fail.fail;
  import static org.mockito.Mockito.mock;
  import static org.mockito.Mockito.when;
  
  class ExponentialBackoffRetryPolicyTest
  {
      Request mockRequest;
      HttpResponse mockResponse;
  
      @BeforeEach
      public void setup()
      {
          mockRequest = mock(Request.class);
          mockResponse = mock(HttpResponse.class);
          when(mockRequest.requestURI()).thenReturn("/api/uri");
      }
  
      @Test
      void testOverflows()
      {
          long delay = new ExponentialBackoffRetryPolicy(1, 1, 0)
                       .retryDelayMillis(64); // 2 ^ (64 - 1) + 1 overflows
          assertThat(delay).as("Should not overflow when the exponential grows larger")
                           .isEqualTo(Long.MAX_VALUE);
  
          delay = new ExponentialBackoffRetryPolicy(1, 2, 0)
                  .retryDelayMillis(63); // 2 * 2 ^ (63 - 1) + 1 overflows
          assertThat(delay).isEqualTo(Long.MAX_VALUE);
  
          delay = new ExponentialBackoffRetryPolicy(1, 200, 0)
                  .retryDelayMillis(56);
          assertThat(delay).as("If the number of retries is greater than or equals to 56, the value will overflow")
                           .isEqualTo(Long.MAX_VALUE);
      }
  
      @Test
      void testCompletesWithOKStatusCode() throws ExecutionException, InterruptedException
      {
          when(mockResponse.statusCode()).thenReturn(OK.code());
  
          CompletableFuture<HttpResponse> future = new CompletableFuture<>();
          new ExponentialBackoffRetryPolicy().onResponse(future, mockRequest, mockResponse, null, 1, false,
                                                         (attempts, retryDelayMillis) -> fail("Should never retry"));
          future.join();
          assertThat(future.isDone()).isTrue();
          assertThat(future.get()).isSameAs(mockResponse);
      }
  
      @ParameterizedTest(name = "{index} => canRetryOnADifferentHost={0}")
      @ValueSource(booleans = { true, false })
      void testRetriesWhenThrowableIsProvided(boolean canRetryOnADifferentHost)
      {
          IllegalArgumentException throwable = new IllegalArgumentException("Connection Refused");
          testWithRetries(mockRequest, null, throwable, 10, 100,
                          canRetryOnADifferentHost ? 0 : 100, 1_000, canRetryOnADifferentHost);
      }
  
      @Test
      void testExponentialBackoffOnServerError()
      {
          when(mockResponse.statusCode()).thenReturn(INTERNAL_SERVER_ERROR.code());
          testWithRetries(mockRequest, mockResponse, null, 5, 200, 200, 10_000, false);
          // should not exceed the configuredMaxRetryDelayMillis
          testWithRetries(mockRequest, mockResponse, null, 30, 200, 200, 10_000, false);
          testWithRetries(mockRequest, mockResponse, null, 10, 150, 0, 1_000, true);
          // no maximum configured for max retry delay millis
          testWithRetries(mockRequest, mockResponse, null, 30, 200, 200, -1, false);
      }
  
      private static void testWithRetries(Request request, HttpResponse response, Throwable throwable,
                                          int configuredMaxRetries, int configuredRetryDelayMillis,
                                          int originalExpectedRetryDelayMillis,
                                          int configuredMaxRetryDelayMillis, boolean canRetryOnADifferentHost)
      {
          RetryPolicy retryPolicy = new ExponentialBackoffRetryPolicy(configuredMaxRetries, configuredRetryDelayMillis,
                                                                      configuredMaxRetryDelayMillis);
          CompletableFuture<HttpResponse> future = new CompletableFuture<>();
          AtomicLong expectedRetryDelayMillis = new AtomicLong(originalExpectedRetryDelayMillis);
          for (int currentAttempt = 1; currentAttempt <= configuredMaxRetries; currentAttempt++)
          {
              // retries on error
              int expectedNextAttempt = currentAttempt + 1;
              retryPolicy.onResponse(future, request, response, throwable, currentAttempt, canRetryOnADifferentHost,
                                     (attempts, retryDelayMillis) -> {
                                         if (expectedNextAttempt > configuredMaxRetries)
                                         {
                                             fail("Should never retry");
                                         }
                                         else
                                         {
                                             assertThat(attempts).isEqualTo(expectedNextAttempt);
                                             assertThat(retryDelayMillis).isEqualTo(expectedRetryDelayMillis.get());
                                         }
                                     });
              expectedRetryDelayMillis.updateAndGet(current -> configuredMaxRetryDelayMillis > 0
                                                               ? Math.min(configuredMaxRetryDelayMillis, current * 2)
                                                               : current * 2);
          }
  
          assertThatExceptionOfType(CompletionException.class)
          .isThrownBy(future::join)
          .withCauseInstanceOf(RetriesExhaustedException.class)
          .withMessageContaining("Unable to complete request '/api/uri' after " + configuredMaxRetries + " attempts");
          assertThat(future.isCompletedExceptionally()).isTrue();
      }
  }
  