/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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
 *
 *      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.juneau.utils;

import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.util.*;

import org.apache.juneau.*;
import org.apache.juneau.collections.*;
import org.apache.juneau.commons.collections.*;

/**
 * Utility class for comparing two versions of a POJO.
 *
 * <p>
 *
 * <p class='bjava'>
 *    <jc>// Two beans to compare.</jc>
 *    MyBean <jv>bean1</jv>, <jv>bean2</jv>;
 *
 * <jc>// Get differences.</jc>
 *    BeanDiff <jv>beanDiff</jv> = BeanDiff.<jsm>create</jsm>(<jv>bean1</jv>, <jv>bean2</jv>).exclude(<js>"fooProperty"</js>).build();
 *
 *    <jc>// Check for differences.</jc>
 *    <jk>boolean</jk> <jv>hasDiff</jv> = <jv>beanDiff</jv>.hasDiffs();
 *
 *    JsonMap <jv>v1Diffs</jv> = <jv>beanDiff</jv>.getV1();  <jc>// Get version 1 differences.</jc>
 *    JsonMap <jv>v2Diffs</jv> = <jv>beanDiff</jv>.getV2();  <jc>// Get version 2 differences.</jc>
 *
 *    <jc>// Display differences.</jc>
 *    System.<jsf>err</jsf>.println(<jv>beanDiff</jv>);
 * </p>
 *
 */
public class BeanDiff {

   /**
    * 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 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.
       */
      public Builder<T> beanContext(BeanContext value) {
         beanContext = value;
         return this;
      }

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

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

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

      /**
       * Specifies the first bean to compare.
       *
       * @param value The first bean to compare.
       * @return This object.
       */
      public Builder<T> first(T value) {
         first = 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.
       */
      public Builder<T> include(Set<String> properties) {
         include = 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.
       */
      public Builder<T> include(String...properties) {
         include = set(properties);
         return this;
      }

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

   /**
    * Create a new builder for this class.
    *
    * @param <T> The bean types.
    * @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);
   }

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

   /**
    * Constructor.
    *
    * @param <T> The bean types.
    * @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;
      var bm1 = first == null ? null : bc.toBeanMap(first);
      var bm2 = second == null ? null : bc.toBeanMap(second);
      var keys = nn(bm1) ? bm1.keySet() : bm2.keySet();
      keys.forEach(k -> {
         if ((include == null || include.contains(k)) && (exclude == null || ! exclude.contains(k))) {
            var o1 = bm1 == null ? null : bm1.get(k);
            var o2 = bm2 == null ? null : bm2.get(k);
            if (neq(o1, o2)) {
               if (nn(o1))
                  v1.put(k, o1);
               if (nn(o2))
                  v2.put(k, o2);
            }
         }
      });
   }

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

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

   /**
    * 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;
   }

   protected FluentMap<String,Object> properties() {
      // @formatter:off
      return mapb_so().buildFluent()
         .a("v1", v1)
         .a("v2", v2);
      // @formatter:on
   }

   @Override
   public String toString() {
      return r(properties());
   }
}