/*
    * Copyright 2017 LINE Corporation
    *
    * LINE Corporation 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:
    *
    *   https://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 com.linecorp.centraldogma.server.internal.storage.repository;
  
  import static java.util.Objects.requireNonNull;
  
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import com.google.common.base.MoreObjects;
  
  import com.linecorp.centraldogma.server.storage.repository.Repository;
  
  // XXX(trustin): Consider using reflection or AOP so that it takes less effort to add more call types.
  public abstract class CacheableCall<T> {
  
      private static final Lock[] locks;
  
      static {
          locks = new Lock[8192];
          for (int i = 0; i < locks.length; i++) {
              locks[i] = new ReentrantLock();
          }
      }
  
      final Repository repo;
  
      protected CacheableCall(Repository repo) {
          this.repo = requireNonNull(repo, "repo");
      }
  
      public final Repository repo() {
          return repo;
      }
  
      public final Lock coarseGrainedLock() {
          return locks[Math.abs(hashCode() % locks.length)];
      }
  
      protected abstract int weigh(T value);
  
      public abstract CompletableFuture<T> execute();
  
      @Override
      public int hashCode() {
          return System.identityHashCode(repo);
      }
  
      @Override
      public boolean equals(Object obj) {
          if (obj == null) {
              return false;
          }
  
          if (obj == this) {
              return true;
          }
  
          if (getClass() != obj.getClass()) {
              return false;
          }
  
          final CacheableCall<?> that = (CacheableCall<?>) obj;
          return repo == that.repo;
      }
  
      @Override
      public final String toString() {
          final MoreObjects.ToStringHelper helper =
                  MoreObjects.toStringHelper(this)
                             .add("repo", repo.parent().name() + '/' + repo.name());
          toString(helper);
          return helper.toString();
      }
  
      protected abstract void toString(MoreObjects.ToStringHelper helper);
  }