content: /*
   * 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.bookkeeper.stream.storage.impl;
  
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.ScheduledExecutorService;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.bookkeeper.stream.proto.storage.StatusCode;
  
  /**
   * Operation Processor.
   */
  public abstract class AsyncOperationProcessor<ReqT, RespT, StateT> {
  
      public CompletableFuture<RespT> process(StateT state,
                                              ReqT request,
                                              ScheduledExecutorService executor) {
          CompletableFuture<RespT> future = FutureUtils.createFuture();
          executor.submit(() -> processRequest(
              future,
              state,
              request));
          return future;
      }
  
      protected abstract StatusCode verifyRequest(StateT state,
                                                  ReqT request);
  
      protected abstract RespT failRequest(StatusCode code);
  
      protected abstract CompletableFuture<RespT> doProcessRequest(StateT state, ReqT request);
  
      protected void processRequest(CompletableFuture<RespT> future,
                                    StateT state,
                                    ReqT request) {
          try {
              StatusCode code = verifyRequest(state, request);
              if (StatusCode.SUCCESS != code) {
                  future.complete(failRequest(code));
              } else {
                  doProcessRequest(state, request).whenComplete((value, causeB) -> {
                      if (null == causeB) {
                          future.complete(value);
                      } else {
                          future.completeExceptionally(causeB);
                      }
                  });
              }
          } catch (Throwable cause) {
              future.completeExceptionally(cause);
          }
      }
  
  }
  