/*
    * 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.common;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static java.util.Objects.requireNonNull;
  
  import java.util.List;
  
  import javax.annotation.Nullable;
  
  import com.fasterxml.jackson.databind.JsonNode;
  import com.google.common.base.MoreObjects;
  import com.google.common.collect.ImmutableList;
  
  /**
   * A merged entry in a repository.
   *
   * @param <T> the content type. It is {@link JsonNode} because only JSON merge is currently supported.
   */
  public final class MergedEntry<T> implements ContentHolder<T> {
  
      /**
       * Returns a newly-created {@link MergedEntry}.
       *
       * @param revision the revision of the {@link MergedEntry}
       * @param type the type of the {@link MergedEntry}
       * @param content the content of the {@link MergedEntry}
       * @param <T> the content type. It is {@link JsonNode} because only JSON merge is currently supported.
       * @param paths the paths which participated to compose the {@link MergedEntry}
       */
      public static <T> MergedEntry<T> of(Revision revision, EntryType type, T content, String... paths) {
          return new MergedEntry<>(revision, type, content, ImmutableList.copyOf(requireNonNull(paths, "paths")));
      }
  
      /**
       * Returns a newly-created {@link MergedEntry}.
       *
       * @param revision the revision of the {@link MergedEntry}
       * @param type the type of the {@link MergedEntry}
       * @param content the content of the {@link MergedEntry}
       * @param <T> the content type. It is {@link JsonNode} because only JSON merge is currently supported.
       * @param paths the paths which participated to compose the {@link MergedEntry}
       */
      public static <T> MergedEntry<T> of(Revision revision, EntryType type, T content, Iterable<String> paths) {
          return new MergedEntry<>(revision, type, content, paths);
      }
  
      private final Revision revision;
      private final EntryType type;
      private final List<String> paths;
      private final T content;
      @Nullable
      private String contentAsText;
      @Nullable
      private String contentAsPrettyText;
  
      /**
       * Creates a new instance.
       */
      private MergedEntry(Revision revision, EntryType type, T content, Iterable<String> paths) {
          this.revision = requireNonNull(revision, "revision");
          this.type = requireNonNull(type, "type");
          requireNonNull(content, "content");
          final Class<?> entryType = type.type();
          checkArgument(entryType.isAssignableFrom(content.getClass()),
                        "content type: %s (expected: %s)", content.getClass(), entryType);
          this.content = content;
          this.paths = ImmutableList.copyOf(requireNonNull(paths, "paths"));
      }
  
      // TODO(minwoox) Move this method upto ContentHolder when we include the revision in Entry as well.
      /**
       * Returns the {@link Revision} of this {@link MergedEntry}.
       */
      public Revision revision() {
          return revision;
      }
  
      @Override
      public EntryType type() {
          return type;
      }
  
      @Override
     public T content() {
         return content;
     }
 
     /**
      * Returns the paths which participated to compose the {@link MergedEntry}.
      */
     public List<String> paths() {
         return paths;
     }
 
     @Override
     public String contentAsText() {
         if (contentAsText == null) {
             contentAsText = ContentHolder.super.contentAsText();
         }
         return contentAsText;
     }
 
     @Override
     public String contentAsPrettyText() {
         if (contentAsPrettyText == null) {
             contentAsPrettyText = ContentHolder.super.contentAsPrettyText();
         }
         return contentAsPrettyText;
     }
 
     @Override
     public int hashCode() {
         return (revision.hashCode() * 31 + type.hashCode()) * 31 + content.hashCode();
     }
 
     @Override
     public boolean equals(Object o) {
         if (this == o) {
             return true;
         }
         if (!(o instanceof MergedEntry)) {
             return false;
         }
         @SuppressWarnings("unchecked")
         final MergedEntry<T> that = (MergedEntry<T>) o;
         return revision.equals(that.revision) &&
                type == that.type &&
                content.equals(that.content) &&
                paths.equals(that.paths);
     }
 
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
                           .add("revision", revision())
                           .add("type", type())
                           .add("content", contentAsText())
                           .add("paths", paths())
                           .toString();
     }
 }