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// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
// *                                                                                                                         *
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// ***************************************************************************************************************************
package org.apache.juneau.utils;

import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.annotation.Bean;
import org.apache.juneau.internal.*;
import org.apache.juneau.marshall.SimpleJson;

/**
 * Utility class for comparing two versions of a POJO.
 *
 * <p class='bpcode w800'>
 *    <jc>// Two beans to compare.</jc>
 *    MyBean bean1, bean2;
 *
 * <jc>// Get differences.</jc>
 *    BeanDiff bf = BeanDiff.<jsm>create</jsm>(bean1, bean2).exclude(<js>"fooProperty"</js>).build();
 *
 *    <jc>// Check for differences.</jc>
 *    <jk>boolean</jk> b = bf.hasDiffs();
 *
 *    ObjectMap v1 = bf.getV1();  <jc>// Get version 1 differences.</jc>
 *    ObjectMap v2 = bf.getV2();  <jc>// Get version 2 differences.</jc>
 *
 *    <jc>// Display differences.</jc>
 *    System.<jsf>err</jsf>.println(bf);
 * </p>
 */
@Bean(bpi="v1,v2")
public class BeanDiff {

   private ObjectMap v1 = new ObjectMap(), v2 = new ObjectMap();

   /**
    * Constructor.
    *
    * @param bc The bean context to use for comparing beans.
    * @param first The first bean to compare.
    * @param second The second bean to compare.
    * @param include
    *    Optional properties to include in the comparison.
    *    <br>If <jk>null</jk>, all properties are included.
    * @param exclude
    *    Optional properties to exclude in the comparison.
    *    <br>If <jk>null</jk>, no properties are excluded.
    */
   @SuppressWarnings("null")
   public <T> BeanDiff(BeanContext bc, T first, T second, Set<String> include, Set<String> exclude) {
      if (first == null && second == null)
         return;
      BeanSession bs = bc.createBeanSession();
      BeanMap<?> bm1 = first == null ? null : bs.toBeanMap(first);
      BeanMap<?> bm2 = second == null ? null : bs.toBeanMap(second);
      Set<String> keys = bm1 != null ? bm1.keySet() : bm2.keySet();
      for (String k : keys) {
         if ((include == null || include.contains(k)) && (exclude == null || ! exclude.contains(k))) {
            Object o1 = bm1 == null ? null : bm1.get(k);
            Object o2 = bm2 == null ? null : bm2.get(k);
            if (! ObjectUtils.equals(o1, o2)) {
               if (o1 != null)
                  v1.put(k, o1);
               if (o2 != null)
                  v2.put(k, o2);
            }
         }
      }
   }

   /**
    * Create a new builder for this class.
    *
    * @param first The first bean to compare.
    * @param second The second bean to compare.
    * @return A new builder.
    */
   public static <T> Builder<T> create(T first, T second) {
      return new Builder<T>().first(first).second(second);
   }

   /**
    * Builder class.
    *
    * @param <T> The bean type.
    */
   public static class Builder<T> {
      T first, second;
      BeanContext beanContext = BeanContext.DEFAULT;
      Set<String> include, exclude;

      /**
       * Specifies the first bean to compare.
       *
       * @param value The first bean to compare.
       * @return This object (for method chaining).
       */
      public Builder<T> first(T value) {
         this.first = value;
         return this;
      }

      /**
       * Specifies the second bean to compare.
       *
       * @param value The first bean to compare.
       * @return This object (for method chaining).
       */
      public Builder<T> second(T value) {
         this.second = value;
         return this;
      }

      /**
       * Specifies the bean context to use for introspecting beans.
       *
       * <p>
       * If not specified, uses {@link BeanContext#DEFAULT}.
       *
       * @param value The bean context to use for introspecting beans.
       * @return This object (for method chaining).
       */
      public Builder<T> beanContext(BeanContext value) {
         this.beanContext = value;
         return this;
      }

      /**
       * Specifies the properties to include in the comparison.
       *
       * <p>
       * If not specified, compares all properties.
       *
       * @param properties The properties to include in the comparison.
       * @return This object (for method chaining).
       */
      public Builder<T> include(String...properties) {
         include = new HashSet<>(Arrays.asList(properties));
         return this;
      }

      /**
       * Specifies the properties to include in the comparison.
       *
       * <p>
       * If not specified, compares all properties.
       *
       * @param properties The properties to include in the comparison.
       * @return This object (for method chaining).
       */
      public Builder<T> include(Set<String> properties) {
         include = properties;
         return this;
      }

      /**
       * Specifies the properties to exclude from the comparison.
       *
       * @param properties The properties to exclude from the comparison.
       * @return This object (for method chaining).
       */
      public Builder<T> exclude(String...properties) {
         exclude = new HashSet<>(Arrays.asList(properties));
         return this;
      }

      /**
       * Specifies the properties to exclude from the comparison.
       *
       * @param properties The properties to exclude from the comparison.
       * @return This object (for method chaining).
       */
      public Builder<T> exclude(Set<String> properties) {
         exclude = properties;
         return this;
      }

      /**
       * Build the differences.
       *
       * @return A new {@link BeanDiff} object.
       */
      public BeanDiff build() {
         return new BeanDiff(beanContext, first, second, include, exclude);
      }

   }

   /**
    * Returns <jk>true</jk> if the beans had differences.
    *
    * @return <jk>true</jk> if the beans had differences.
    */
   public boolean hasDiffs() {
      return v1.size() > 0 || v2.size() > 0;
   }

   /**
    * Returns the differences in the first bean.
    *
    * @return The differences in the first bean.
    */
   public ObjectMap getV1() {
      return v1;
   }

   /**
    * Returns the differences in the second bean.
    *
    * @return The differences in the second bean.
    */
   public ObjectMap getV2() {
      return v2;
   }

   @Override
   public String toString() {
      return SimpleJson.DEFAULT.toString(this);
   }
}