/*
    *    Copyright 2009-2021 the original author or authors.
    *
    *    Licensed 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.ibatis.cache;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.StringJoiner;
  
  import org.apache.ibatis.reflection.ArrayUtil;
  
  /**
   * @author Clinton Begin
   */
  public class CacheKey implements Cloneable, Serializable {
  
    private static final long serialVersionUID = 1146682552656046210L;
  
    public static final CacheKey NULL_CACHE_KEY = new CacheKey() {
  
      @Override
      public void update(Object object) {
        throw new CacheException("Not allowed to update a null cache key instance.");
      }
  
      @Override
      public void updateAll(Object[] objects) {
        throw new CacheException("Not allowed to update a null cache key instance.");
      }
    };
  
    private static final int DEFAULT_MULTIPLIER = 37;
    private static final int DEFAULT_HASHCODE = 17;
  
    private final int multiplier;
    private int hashcode;
    private long checksum;
    private int count;
    // 8/21/2017 - Sonarlint flags this as needing to be marked transient. While true if content is not serializable, this
    // is not always true and thus should not be marked transient.
    private List<Object> updateList;
  
    public CacheKey() {
      this.hashcode = DEFAULT_HASHCODE;
      this.multiplier = DEFAULT_MULTIPLIER;
      this.count = 0;
      this.updateList = new ArrayList<>();
    }
  
    public CacheKey(Object[] objects) {
      this();
      updateAll(objects);
    }
  
    public int getUpdateCount() {
      return updateList.size();
    }
  
    public void update(Object object) {
      int baseHashCode = object == null ? 1 : ArrayUtil.hashCode(object);
  
      count++;
      checksum += baseHashCode;
      baseHashCode *= count;
  
      hashcode = multiplier * hashcode + baseHashCode;
  
      updateList.add(object);
    }
  
    public void updateAll(Object[] objects) {
      for (Object o : objects) {
        update(o);
      }
    }
  
    @Override
    public boolean equals(Object object) {
      if (this == object) {
        return true;
      }
      if (!(object instanceof CacheKey)) {
        return false;
      }
  
      final CacheKey cacheKey = (CacheKey) object;
 
     if (hashcode != cacheKey.hashcode) {
       return false;
     }
     if (checksum != cacheKey.checksum) {
       return false;
     }
     if (count != cacheKey.count) {
       return false;
     }
 
     for (int i = 0; i < updateList.size(); i++) {
       Object thisObject = updateList.get(i);
       Object thatObject = cacheKey.updateList.get(i);
       if (!ArrayUtil.equals(thisObject, thatObject)) {
         return false;
       }
     }
     return true;
   }
 
   @Override
   public int hashCode() {
     return hashcode;
   }
 
   @Override
   public String toString() {
     StringJoiner returnValue = new StringJoiner(":");
     returnValue.add(String.valueOf(hashcode));
     returnValue.add(String.valueOf(checksum));
     updateList.stream().map(ArrayUtil::toString).forEach(returnValue::add);
     return returnValue.toString();
   }
 
   @Override
   public CacheKey clone() throws CloneNotSupportedException {
     CacheKey clonedCacheKey = (CacheKey) super.clone();
     clonedCacheKey.updateList = new ArrayList<>(updateList);
     return clonedCacheKey;
   }
 
 }