/*
 * 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 java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.lang3.Validate;

 A DiffResult contains a collection of the differences between two Diffable objects. Typically these differences are displayed using toString() method, which returns a string describing the fields that differ between the objects. 
 Use a DiffBuilder to build a DiffResult comparing two objects. 
Type parameters:
<T> – type of the left and right object.
Since:
3.3/**
 * <p>
 * A {@code DiffResult} contains a collection of the differences between two
 * {@link Diffable} objects. Typically these differences are displayed using
 * {@link #toString()} method, which returns a string describing the fields that
 * differ between the objects.
 * </p>
 * <p>
 * Use a {@link DiffBuilder} to build a {@code DiffResult} comparing two objects.
 * </p>
 * @param <T> type of the left and right object.
 *
 * @since 3.3
 */
public class DiffResult<T> implements Iterable<Diff<?>> {

    
 The String returned when the objects have no differences: "" 
/**
     * <p>
     * The {@code String} returned when the objects have no differences:
     * {@value}
     * </p>
     */
    public static final String OBJECTS_SAME_STRING = "";

    private static final String DIFFERS_STRING = "differs from";

    private final List<Diff<?>> diffs;
    private final T lhs;
    private final T rhs;
    private final ToStringStyle style;

    
 Creates a DiffResult containing the differences between two objects. 
Params:
lhs – 
           the left hand object
rhs – 
           the right hand object
diffs – 
           the list of differences, may be empty
style –  the style to use for the toString() method. May be null, in which case ToStringStyle.DEFAULT_STYLE is used
Throws:
NullPointerException – if lhs, rhs or diffs is null/**
     * <p>
     * Creates a {@link DiffResult} containing the differences between two
     * objects.
     * </p>
     *
     * @param lhs
     *            the left hand object
     * @param rhs
     *            the right hand object
     * @param diffs
     *            the list of differences, may be empty
     * @param style
     *            the style to use for the {@link #toString()} method. May be
     *            {@code null}, in which case
     *            {@link ToStringStyle#DEFAULT_STYLE} is used
     * @throws NullPointerException if {@code lhs}, {@code rhs} or {@code diffs} is {@code null}
     */
    DiffResult(final T lhs, final T rhs, final List<Diff<?>> diffs,
            final ToStringStyle style) {
        Validate.notNull(lhs, "Left hand object cannot be null");
        Validate.notNull(rhs, "Right hand object cannot be null");
        Validate.notNull(diffs, "List of differences cannot be null");

        this.diffs = diffs;
        this.lhs = lhs;
        this.rhs = rhs;

        if (style == null) {
            this.style = ToStringStyle.DEFAULT_STYLE;
        } else {
            this.style = style;
        }
    }

    
Returns the object the right object has been compared to.
Returns:
the left object of the diff
Since:
3.10/**
     * <p>Returns the object the right object has been compared to.</p>
     *
     * @return the left object of the diff
     * @since 3.10
     */
    public T getLeft() {
        return this.lhs;
    }

    
Returns the object the left object has been compared to.
Returns:
the right object of the diff
Since:
3.10/**
     * <p>Returns the object the left object has been compared to.</p>
     *
     * @return the right object of the diff
     * @since 3.10
     */
    public T getRight() {
        return this.rhs;
    }

    
 Returns an unmodifiable list of Diffs. The list may be empty if there were no differences between the objects. 
Returns:
an unmodifiable list of Diffs/**
     * <p>
     * Returns an unmodifiable list of {@code Diff}s. The list may be empty if
     * there were no differences between the objects.
     * </p>
     *
     * @return an unmodifiable list of {@code Diff}s
     */
    public List<Diff<?>> getDiffs() {
        return Collections.unmodifiableList(diffs);
    }

    

Returns the number of differences between the two objects.

Returns:
the number of differences/**
     * <p>
     * Returns the number of differences between the two objects.
     * </p>
     *
     * @return the number of differences
     */
    public int getNumberOfDiffs() {
        return diffs.size();
    }

    
 Returns the style used by the toString() method. 
Returns:
the style/**
     * <p>
     * Returns the style used by the {@link #toString()} method.
     * </p>
     *
     * @return the style
     */
    public ToStringStyle getToStringStyle() {
        return style;
    }

    
 Builds a String description of the differences contained within this DiffResult. A ToStringBuilder is used for each object and the style of the output is governed by the ToStringStyle passed to the constructor. 
 If there are no differences stored in this list, the method will return DiffResult<T>.OBJECTS_SAME_STRING. Otherwise, using the example given in Diffable and ToStringStyle.SHORT_PREFIX_STYLE, an output might be: 
Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]


This indicates that the objects differ in name and age, but not in
smoking status.

 To use a different ToStringStyle for an instance of this class, use toString(ToStringStyle). 
Returns:
a String description of the differences./**
     * <p>
     * Builds a {@code String} description of the differences contained within
     * this {@code DiffResult}. A {@link ToStringBuilder} is used for each object
     * and the style of the output is governed by the {@code ToStringStyle}
     * passed to the constructor.
     * </p>
     *
     * <p>
     * If there are no differences stored in this list, the method will return
     * {@link #OBJECTS_SAME_STRING}. Otherwise, using the example given in
     * {@link Diffable} and {@link ToStringStyle#SHORT_PREFIX_STYLE}, an output
     * might be:
     * </p>
     *
     * <pre>
     * Person[name=John Doe,age=32] differs from Person[name=Joe Bloggs,age=26]
     * </pre>
     *
     * <p>
     * This indicates that the objects differ in name and age, but not in
     * smoking status.
     * </p>
     *
     * <p>
     * To use a different {@code ToStringStyle} for an instance of this class,
     * use {@link #toString(ToStringStyle)}.
     * </p>
     *
     * @return a {@code String} description of the differences.
     */
    @Override
    public String toString() {
        return toString(style);
    }

    
 Builds a String description of the differences contained within this DiffResult, using the supplied ToStringStyle. 
Params:
style –  the ToStringStyle to use when outputting the objects
Returns:
a String description of the differences./**
     * <p>
     * Builds a {@code String} description of the differences contained within
     * this {@code DiffResult}, using the supplied {@code ToStringStyle}.
     * </p>
     *
     * @param style
     *            the {@code ToStringStyle} to use when outputting the objects
     *
     * @return a {@code String} description of the differences.
     */
    public String toString(final ToStringStyle style) {
        if (diffs.isEmpty()) {
            return OBJECTS_SAME_STRING;
        }

        final ToStringBuilder lhsBuilder = new ToStringBuilder(lhs, style);
        final ToStringBuilder rhsBuilder = new ToStringBuilder(rhs, style);

        for (final Diff<?> diff : diffs) {
            lhsBuilder.append(diff.getFieldName(), diff.getLeft());
            rhsBuilder.append(diff.getFieldName(), diff.getRight());
        }

        return String.format("%s %s %s", lhsBuilder.build(), DIFFERS_STRING,
                rhsBuilder.build());
    }

    
 Returns an iterator over the Diff objects contained in this list. 
Returns:
the iterator/**
     * <p>
     * Returns an iterator over the {@code Diff} objects contained in this list.
     * </p>
     *
     * @return the iterator
     */
    @Override
    public Iterator<Diff<?>> iterator() {
        return diffs.iterator();
    }
}