/*
 * Copyright (c) 2016 Mockito contributors
 * This program is made available under the terms of the MIT License.
 */
package org.mockito.internal.stubbing.defaultanswers;

import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.Stream;
import org.mockito.internal.util.MockUtil;
import org.mockito.internal.util.Primitives;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.mock.MockName;
import org.mockito.stubbing.Answer;

import static org.mockito.internal.util.ObjectMethodsGuru.isCompareToMethod;
import static org.mockito.internal.util.ObjectMethodsGuru.isToStringMethod;

/**
 * Default answer of every Mockito mock.
 * <ul>
 * <li>Returns appropriate primitive for primitive-returning methods</li>
 * <li>Returns consistent values for primitive wrapper classes (e.g. int-returning method returns 0 <strong>and</strong>
 *     Integer-returning method returns 0, too)</li>
 * <li>Returns empty collection for collection-returning methods (works for most commonly used collection types)</li>
 * <li>Returns empty array for array-returning methods</li>
 * <li>Returns description of mock for toString() method</li>
 * <li>Returns zero if references are equals otherwise non-zero for Comparable#compareTo(T other) method (see issue 184)</li>
 * <li>Returns an {@link java.util.Optional#empty() empty Optional} for Optional. Similarly for primitive optional variants.</li>
 * <li>Returns an {@link java.util.stream.Stream#empty() empty Stream} for Stream. Similarly for primitive stream variants.</li>
 * <li>Returns null for everything else</li>
 * </ul>
 */
public class ReturnsEmptyValues implements Answer<Object>, Serializable {

    private static final long serialVersionUID = 1998191268711234347L;


    public Object answer(InvocationOnMock invocation) {
        if (isToStringMethod(invocation.getMethod())) {
            Object mock = invocation.getMock();
            MockName name = MockUtil.getMockName(mock);
            if (name.isDefault()) {
                return "Mock for " + MockUtil.getMockSettings(mock).getTypeToMock().getSimpleName() + ", hashCode: " + mock.hashCode();
            } else {
                return name.toString();
            }
        } else if (isCompareToMethod(invocation.getMethod())) {
            //see issue 184.
            //mocks by default should return 0 if references are the same, otherwise some other value because they are not the same. Hence we return 1 (anything but 0 is good).
            //Only for compareTo() method by the Comparable interface
            return invocation.getMock() == invocation.getArgument(0) ? 0 : 1;
        }

        Class<?> returnType = invocation.getMethod().getReturnType();
        return returnValueFor(returnType);
    }

    Object returnValueFor(Class<?> type) {
        if (Primitives.isPrimitiveOrWrapper(type)) {
            return Primitives.defaultValue(type);
            //new instances are used instead of Collections.emptyList(), etc.
            //to avoid UnsupportedOperationException if code under test modifies returned collection
        } else if (type.isArray()) {
            Class<?> componentType = type.getComponentType();
            return Array.newInstance(componentType, 0);
        } else if (type == Iterable.class) {
            return new ArrayList<Object>(0);
        } else if (type == Collection.class) {
            return new LinkedList<Object>();
        } else if (type == Set.class) {
            return new HashSet<Object>();
        } else if (type == HashSet.class) {
            return new HashSet<Object>();
        } else if (type == SortedSet.class) {
            return new TreeSet<Object>();
        } else if (type == TreeSet.class) {
            return new TreeSet<Object>();
        } else if (type == LinkedHashSet.class) {
            return new LinkedHashSet<Object>();
        } else if (type == List.class) {
            return new LinkedList<Object>();
        } else if (type == LinkedList.class) {
            return new LinkedList<Object>();
        } else if (type == ArrayList.class) {
            return new ArrayList<Object>();
        } else if (type == Map.class) {
            return new HashMap<Object, Object>();
        } else if (type == HashMap.class) {
            return new HashMap<Object, Object>();
        } else if (type == SortedMap.class) {
            return new TreeMap<Object, Object>();
        } else if (type == TreeMap.class) {
            return new TreeMap<Object, Object>();
        } else if (type == LinkedHashMap.class) {
            return new LinkedHashMap<Object, Object>();
        } else if (type == Optional.class) {
            return Optional.empty();
        } else if (type == OptionalDouble.class) {
            return OptionalDouble.empty();
        } else if (type == OptionalInt.class) {
            return OptionalInt.empty();
        } else if (type == OptionalLong.class) {
            return OptionalLong.empty();
        } else if (type == Stream.class) {
            return Stream.empty();
        } else if (type == DoubleStream.class) {
            return DoubleStream.empty();
        } else if (type == IntStream.class) {
            return IntStream.empty();
        } else if (type == LongStream.class) {
            return LongStream.empty();
        }

        //Let's not care about the rest of collections.
        return null;
    }
}