/*
    * Copyright 2018 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.cache;
  
  import static com.google.common.base.Preconditions.checkState;
  import static com.linecorp.centraldogma.internal.Util.validateJsonFilePath;
  import static java.util.Objects.requireNonNull;
  
  import java.util.List;
  import java.util.Objects;
  import java.util.concurrent.CompletableFuture;
  
  import javax.annotation.Nullable;
  
  import com.google.common.base.MoreObjects.ToStringHelper;
  
  import com.linecorp.centraldogma.common.MergeQuery;
  import com.linecorp.centraldogma.common.MergeSource;
  import com.linecorp.centraldogma.common.MergedEntry;
  import com.linecorp.centraldogma.common.Revision;
  import com.linecorp.centraldogma.server.internal.storage.repository.CacheableCall;
  import com.linecorp.centraldogma.server.storage.repository.Repository;
  
  final class CacheableMergeQueryCall extends CacheableCall<MergedEntry<?>> {
  
      private final Revision revision;
      private final MergeQuery<?> query;
      private final int hashCode;
  
      @Nullable
      MergedEntry<?> computedValue;
  
      CacheableMergeQueryCall(Repository repo, Revision revision, MergeQuery<?> query) {
          super(repo);
          this.revision = requireNonNull(revision, "revision");
          this.query = requireNonNull(query, "query");
          // Only JSON files can currently be merged.
          query.mergeSources().forEach(path -> validateJsonFilePath(path.path(), "path"));
  
          hashCode = Objects.hash(revision, query) * 31 + System.identityHashCode(repo);
  
          assert !revision.isRelative();
      }
  
      @Override
      protected int weigh(MergedEntry<?> value) {
          int weight = 0;
          final List<MergeSource> mergeSources = query.mergeSources();
          weight += mergeSources.size();
          for (MergeSource mergeSource : mergeSources) {
              weight += mergeSource.path().length();
          }
          final List<String> expressions = query.expressions();
          weight += expressions.size();
          for (String expression : expressions) {
              weight += expression.length();
          }
          if (value != null) {
              weight += value.contentAsText().length();
          }
          return weight;
      }
  
      @Override
      public CompletableFuture<MergedEntry<?>> execute() {
          checkState(computedValue != null, "computedValue is not set yet.");
          return CompletableFuture.completedFuture(computedValue);
      }
  
      void computedValue(MergedEntry<?> computedValue) {
          checkState(this.computedValue == null, "computedValue is already set.");
          this.computedValue = requireNonNull(computedValue, "computedValue");
      }
  
      @Override
      public int hashCode() {
          return hashCode;
      }
  
      @Override
      public boolean equals(Object o) {
          if (!super.equals(o)) {
              return false;
          }
  
         final CacheableMergeQueryCall that = (CacheableMergeQueryCall) o;
         return revision.equals(that.revision) &&
                query.equals(that.query);
     }
 
     @Override
     protected void toString(ToStringHelper helper) {
         helper.add("revision", revision)
               .add("query", query);
     }
 }