/*
  ==============================================================================

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For the technical preview this file cannot be licensed commercially.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
namespace KeyboardFocusTraverserHelpers
{
    static bool isKeyboardFocusable (const Component* comp, const Component* container)
    {
        return comp->getWantsKeyboardFocus() && container->isParentOf (comp);
    }

    static Component* traverse (Component* current, Component* container,
                                FocusHelpers::NavigationDirection direction)
    {
        if (auto* comp = FocusHelpers::navigateFocus (current, container, direction,
                                                      &Component::isKeyboardFocusContainer))
        {
            if (isKeyboardFocusable (comp, container))
                return comp;

            return traverse (comp, container, direction);
        }

        return nullptr;
    }
}

Component* KeyboardFocusTraverser::getNextComponent (Component* current)
{
    return KeyboardFocusTraverserHelpers::traverse (current, current->findKeyboardFocusContainer(),
                                                    FocusHelpers::NavigationDirection::forwards);
}

Component* KeyboardFocusTraverser::getPreviousComponent (Component* current)
{
    return KeyboardFocusTraverserHelpers::traverse (current, current->findKeyboardFocusContainer(),
                                                    FocusHelpers::NavigationDirection::backwards);
}

Component* KeyboardFocusTraverser::getDefaultComponent (Component* parentComponent)
{
    for (auto* comp : getAllComponents (parentComponent))
        if (KeyboardFocusTraverserHelpers::isKeyboardFocusable (comp, parentComponent))
            return comp;

    return nullptr;
}

std::vector<Component*> KeyboardFocusTraverser::getAllComponents (Component* parentComponent)
{
    std::vector<Component*> components;
    FocusHelpers::findAllComponents (parentComponent,
                                     components,
                                     &Component::isKeyboardFocusContainer);

    auto removePredicate = [parentComponent] (const Component* comp)
    {
        return ! KeyboardFocusTraverserHelpers::isKeyboardFocusable (comp, parentComponent);
    };

    components.erase (std::remove_if (std::begin (components), std::end (components), std::move (removePredicate)),
                      std::end (components));

    return components;
}


//==============================================================================
//==============================================================================
#if JUCE_UNIT_TESTS

struct KeyboardFocusTraverserTests  : public UnitTest
{
    KeyboardFocusTraverserTests()
        : UnitTest ("KeyboardFocusTraverser", UnitTestCategories::gui)
    {}

    void runTest() override
    {
        ScopedJuceInitialiser_GUI libraryInitialiser;
        const MessageManagerLock mml;

        beginTest ("No child wants keyboard focus");
        {
            TestComponent parent;

            expect (traverser.getDefaultComponent (&parent) == nullptr);
            expect (traverser.getAllComponents (&parent).empty());
        }

        beginTest ("Single child wants keyboard focus");
        {
            TestComponent parent;

            parent.children[5].setWantsKeyboardFocus (true);

            auto* defaultComponent = traverser.getDefaultComponent (&parent);

            expect (defaultComponent == &parent.children[5]);
            expect (defaultComponent->getWantsKeyboardFocus());

            expect (traverser.getNextComponent (defaultComponent) == nullptr);
            expect (traverser.getPreviousComponent (defaultComponent) == nullptr);
            expect (traverser.getAllComponents (&parent).size() == 1);
        }

        beginTest ("Multiple children want keyboard focus");
        {
            TestComponent parent;

            Component* focusChildren[]
            {
                &parent.children[1],
                &parent.children[9],
                &parent.children[3],
                &parent.children[5],
                &parent.children[8],
                &parent.children[0]
            };

            for (auto* focusChild : focusChildren)
                focusChild->setWantsKeyboardFocus (true);

            auto allComponents = traverser.getAllComponents (&parent);

            for (auto* focusChild : focusChildren)
                expect (std::find (allComponents.cbegin(), allComponents.cend(), focusChild) != allComponents.cend());

            auto* componentToTest = traverser.getDefaultComponent (&parent);

            for (;;)
            {
                expect (componentToTest->getWantsKeyboardFocus());
                expect (std::find (std::begin (focusChildren), std::end (focusChildren), componentToTest) != std::end (focusChildren));

                componentToTest = traverser.getNextComponent (componentToTest);

                if (componentToTest == nullptr)
                    break;
            }

            int focusOrder = 1;
            for (auto* focusChild : focusChildren)
                focusChild->setExplicitFocusOrder (focusOrder++);

            componentToTest = traverser.getDefaultComponent (&parent);

            for (auto* focusChild : focusChildren)
            {
                expect (componentToTest == focusChild);
                expect (componentToTest->getWantsKeyboardFocus());

                componentToTest = traverser.getNextComponent (componentToTest);
            }
        }

        beginTest ("Single nested child wants keyboard focus");
        {
            TestComponent parent;
            Component grandparent;

            grandparent.addAndMakeVisible (parent);

            auto& focusChild = parent.children[5];

            focusChild.setWantsKeyboardFocus (true);

            expect (traverser.getDefaultComponent (&grandparent) == &focusChild);
            expect (traverser.getDefaultComponent (&parent) == &focusChild);
            expect (traverser.getNextComponent (&focusChild) == nullptr);
            expect (traverser.getPreviousComponent (&focusChild) == nullptr);
            expect (traverser.getAllComponents (&parent).size() == 1);
        }

        beginTest ("Multiple nested children want keyboard focus");
        {
            TestComponent parent;
            Component grandparent;

            grandparent.addAndMakeVisible (parent);

            Component* focusChildren[]
            {
                &parent.children[1],
                &parent.children[4],
                &parent.children[5]
            };

            for (auto* focusChild : focusChildren)
                focusChild->setWantsKeyboardFocus (true);

            auto allComponents = traverser.getAllComponents (&parent);

            expect (std::equal (allComponents.cbegin(), allComponents.cend(), focusChildren,
                                [] (const Component* c1, const Component* c2) { return c1 == c2; }));

            const auto front = *focusChildren;
            const auto back  = *std::prev (std::end (focusChildren));

            expect (traverser.getDefaultComponent (&grandparent) == front);
            expect (traverser.getDefaultComponent (&parent) == front);
            expect (traverser.getNextComponent (front) == *std::next (std::begin (focusChildren)));
            expect (traverser.getPreviousComponent (back) == *std::prev (std::end (focusChildren), 2));

            std::array<Component, 3> otherParents;

            for (auto& p : otherParents)
            {
                grandparent.addAndMakeVisible (p);
                p.setWantsKeyboardFocus (true);
            }

            expect (traverser.getDefaultComponent (&grandparent) == front);
            expect (traverser.getDefaultComponent (&parent) == front);
            expect (traverser.getNextComponent (back) == &otherParents.front());
            expect (traverser.getNextComponent (&otherParents.back()) == nullptr);
            expect (traverser.getAllComponents (&grandparent).size() == numElementsInArray (focusChildren) + otherParents.size());
            expect (traverser.getAllComponents (&parent).size() == (size_t) numElementsInArray (focusChildren));

            for (auto* focusChild : focusChildren)
                focusChild->setWantsKeyboardFocus (false);

            expect (traverser.getDefaultComponent (&grandparent) == &otherParents.front());
            expect (traverser.getDefaultComponent (&parent) == nullptr);
            expect (traverser.getAllComponents (&grandparent).size() == otherParents.size());
            expect (traverser.getAllComponents (&parent).empty());
        }
    }

private:
    struct TestComponent  : public Component
    {
        TestComponent()
        {
            for (auto& child : children)
                addAndMakeVisible (child);
        }

        std::array<Component, 10> children;
    };

    KeyboardFocusTraverser traverser;
};

static KeyboardFocusTraverserTests keyboardFocusTraverserTests;

#endif

} // namespace juce