/*
 * 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.commons.lang3.builder;

import static org.apache.commons.lang3.reflect.FieldUtils.readField;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

import org.apache.commons.lang3.ClassUtils;
import org.apache.commons.lang3.reflect.FieldUtils;

 Assists in implementing Diffable.diff(Object) methods. 

All non-static, non-transient fields (including inherited fields)
of the objects to diff are discovered using reflection and compared
for differences.


To use this class, write code as follows:

public class Person implements Diffable<Person> {
  String name;
  int age;
  boolean smoker;
  ...
  public DiffResult diff(Person obj) {
    // No need for null check, as NullPointerException correct if obj is null
    return new ReflectionDiffBuilder(this, obj, ToStringStyle.SHORT_PREFIX_STYLE)
      .build();
  }
}

 The ToStringStyle passed to the constructor is embedded in the returned DiffResult and influences the style of the DiffResult.toString() method. This style choice can be overridden by calling DiffResult.toString(ToStringStyle). 
Type parameters:
<T> – 
           type of the left and right object to diff.
See Also:
Diffable
Diff
DiffResult
ToStringStyle
Since:
3.6/**
 * <p>
 * Assists in implementing {@link Diffable#diff(Object)} methods.
 * </p>
 * <p>
 * All non-static, non-transient fields (including inherited fields)
 * of the objects to diff are discovered using reflection and compared
 * for differences.
 * </p>
 *
 * <p>
 * To use this class, write code as follows:
 * </p>
 *
 * <pre>
 * public class Person implements Diffable&lt;Person&gt; {
 *   String name;
 *   int age;
 *   boolean smoker;
 *   ...
 *
 *   public DiffResult diff(Person obj) {
 *     // No need for null check, as NullPointerException correct if obj is null
 *     return new ReflectionDiffBuilder(this, obj, ToStringStyle.SHORT_PREFIX_STYLE)
 *       .build();
 *   }
 * }
 * </pre>
 *
 * <p>
 * The {@code ToStringStyle} passed to the constructor is embedded in the
 * returned {@code DiffResult} and influences the style of the
 * {@code DiffResult.toString()} method. This style choice can be overridden by
 * calling {@link DiffResult#toString(ToStringStyle)}.
 * </p>
 * @param <T>
 *            type of the left and right object to diff.
 * @see Diffable
 * @see Diff
 * @see DiffResult
 * @see ToStringStyle
 * @since 3.6
 */
public class ReflectionDiffBuilder<T> implements Builder<DiffResult<T>> {

    private final Object left;
    private final Object right;
    private final DiffBuilder<T> diffBuilder;

    

Constructs a builder for the specified objects with the specified style.

 If lhs == rhs or lhs.equals(rhs) then the builder will not evaluate any calls to append(...) and will return an empty DiffResult when build() is executed. 
Params:
lhs –  this object
rhs – 
           the object to diff against
style –  the style will use when outputting the objects, null uses the default
Throws:
IllegalArgumentException –  if lhs or rhs is null/**
     * <p>
     * Constructs a builder for the specified objects with the specified style.
     * </p>
     *
     * <p>
     * If {@code lhs == rhs} or {@code lhs.equals(rhs)} then the builder will
     * not evaluate any calls to {@code append(...)} and will return an empty
     * {@link DiffResult} when {@link #build()} is executed.
     * </p>
     * @param lhs
     *            {@code this} object
     * @param rhs
     *            the object to diff against
     * @param style
     *            the style will use when outputting the objects, {@code null}
     *            uses the default
     * @throws IllegalArgumentException
     *             if {@code lhs} or {@code rhs} is {@code null}
     */
    public ReflectionDiffBuilder(final T lhs, final T rhs, final ToStringStyle style) {
        this.left = lhs;
        this.right = rhs;
        diffBuilder = new DiffBuilder<>(lhs, rhs, style);
    }

    @Override
    public DiffResult<T> build() {
        if (left.equals(right)) {
            return diffBuilder.build();
        }

        appendFields(left.getClass());
        return diffBuilder.build();
    }

    private void appendFields(final Class<?> clazz) {
        for (final Field field : FieldUtils.getAllFields(clazz)) {
            if (accept(field)) {
                try {
                    diffBuilder.append(field.getName(), readField(field, left, true),
                            readField(field, right, true));
                } catch (final IllegalAccessException ex) {
                    //this can't happen. Would get a Security exception instead
                    //throw a runtime exception in case the impossible happens.
                    throw new InternalError("Unexpected IllegalAccessException: " + ex.getMessage());
                }
            }
        }
    }

    private boolean accept(final Field field) {
        if (field.getName().indexOf(ClassUtils.INNER_CLASS_SEPARATOR_CHAR) != -1) {
            return false;
        }
        if (Modifier.isTransient(field.getModifiers())) {
            return false;
        }
        return !Modifier.isStatic(field.getModifiers());
    }

}