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

   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
{

AccessibilityHandler* AccessibilityHandler::currentlyFocusedHandler = nullptr;

enum class InternalAccessibilityEvent
{
    elementCreated,
    elementDestroyed,
    elementMovedOrResized,
    focusChanged,
    windowOpened,
    windowClosed
};

void notifyAccessibilityEventInternal (const AccessibilityHandler&, InternalAccessibilityEvent);

inline String getAccessibleApplicationOrPluginName()
{
   #if defined (JucePlugin_Name)
    return JucePlugin_Name;
   #else
    if (auto* app = JUCEApplicationBase::getInstance())
        return app->getApplicationName();

    return "JUCE Application";
   #endif
}

AccessibilityHandler::AccessibilityHandler (Component& comp,
                                            AccessibilityRole accessibilityRole,
                                            AccessibilityActions accessibilityActions,
                                            Interfaces interfacesIn)
    : component (comp),
      typeIndex (typeid (component)),
      role (accessibilityRole),
      actions (std::move (accessibilityActions)),
      interfaces (std::move (interfacesIn)),
      nativeImpl (createNativeImpl (*this))
{
    notifyAccessibilityEventInternal (*this, InternalAccessibilityEvent::elementCreated);
}

AccessibilityHandler::~AccessibilityHandler()
{
    giveAwayFocus();
    notifyAccessibilityEventInternal (*this, InternalAccessibilityEvent::elementDestroyed);
}

//==============================================================================
AccessibleState AccessibilityHandler::getCurrentState() const
{
    if (component.isCurrentlyBlockedByAnotherModalComponent()
        && Component::getCurrentlyModalComponent()->isVisible())
        return {};

    auto state = AccessibleState().withFocusable();

    return hasFocus (false) ? state.withFocused() : state;
}

bool AccessibilityHandler::isIgnored() const
{
    return role == AccessibilityRole::ignored || getCurrentState().isIgnored();
}

static bool isComponentVisibleWithinWindow (const Component& comp)
{
    if (auto* peer = comp.getPeer())
        return ! peer->getAreaCoveredBy (comp).getIntersection (peer->getComponent().getLocalBounds()).isEmpty();

    return false;
}

static bool isComponentVisibleWithinParent (Component* comp)
{
    if (auto* parent = comp->getParentComponent())
    {
        if (comp->getBoundsInParent().getIntersection (parent->getLocalBounds()).isEmpty())
            return false;

        return isComponentVisibleWithinParent (parent);
    }

    return true;
}

bool AccessibilityHandler::isVisibleWithinParent() const
{
    return getCurrentState().isAccessibleOffscreen()
          || (isComponentVisibleWithinParent (&component) && isComponentVisibleWithinWindow (component));
}

//==============================================================================
const AccessibilityActions& AccessibilityHandler::getActions() const noexcept
{
    return actions;
}

AccessibilityValueInterface* AccessibilityHandler::getValueInterface() const
{
    return interfaces.value.get();
}

AccessibilityTableInterface* AccessibilityHandler::getTableInterface() const
{
    return interfaces.table.get();
}

AccessibilityCellInterface* AccessibilityHandler::getCellInterface() const
{
    return interfaces.cell.get();
}

AccessibilityTextInterface* AccessibilityHandler::getTextInterface() const
{
    return interfaces.text.get();
}

//==============================================================================
static AccessibilityHandler* findEnclosingHandler (Component* comp)
{
    if (comp != nullptr)
    {
        if (auto* handler = comp->getAccessibilityHandler())
            return handler;

        return findEnclosingHandler (comp->getParentComponent());
    }

    return nullptr;
}

static AccessibilityHandler* getUnignoredAncestor (AccessibilityHandler* handler)
{
    while (handler != nullptr
           && (handler->isIgnored() || ! handler->isVisibleWithinParent())
           && handler->getParent() != nullptr)
    {
        handler = handler->getParent();
    }

    return handler;
}

static AccessibilityHandler* findFirstUnignoredChild (const std::vector<AccessibilityHandler*>& handlers)
{
    if (! handlers.empty())
    {
        const auto iter = std::find_if (handlers.cbegin(), handlers.cend(),
                                        [] (const AccessibilityHandler* handler) { return ! handler->isIgnored() && handler->isVisibleWithinParent(); });

        if (iter != handlers.cend())
            return *iter;

        for (auto* handler : handlers)
            if (auto* unignored = findFirstUnignoredChild (handler->getChildren()))
                return unignored;
    }

    return nullptr;
}

static AccessibilityHandler* getFirstUnignoredDescendant (AccessibilityHandler* handler)
{
    if (handler != nullptr && (handler->isIgnored() || ! handler->isVisibleWithinParent()))
        return findFirstUnignoredChild (handler->getChildren());

    return handler;
}

AccessibilityHandler* AccessibilityHandler::getParent() const
{
    if (auto* focusContainer = component.findFocusContainer())
        return getUnignoredAncestor (findEnclosingHandler (focusContainer));

    return nullptr;
}

std::vector<AccessibilityHandler*> AccessibilityHandler::getChildren() const
{
    if (! component.isFocusContainer() && component.getParentComponent() != nullptr)
        return {};

    const auto addChildComponentHandler = [this] (Component* focusableComponent,
                                                  std::vector<AccessibilityHandler*>& childHandlers)
    {
        if (focusableComponent == nullptr)
            return;

        if (auto* handler = findEnclosingHandler (focusableComponent))
        {
            if (! handler->getCurrentState().isFocusable() || ! isParentOf (handler))
                return;

            if (auto* unignored = getFirstUnignoredDescendant (handler))
                if (std::find (childHandlers.cbegin(), childHandlers.cend(), unignored) == childHandlers.cend())
                    childHandlers.push_back (unignored);
        }
    };

    std::vector<AccessibilityHandler*> children;

    if (auto traverser = component.createFocusTraverser())
    {
        addChildComponentHandler (traverser->getDefaultComponent (&component), children);

        for (auto* focusableChild : traverser->getAllComponents (&component))
            addChildComponentHandler (focusableChild, children);
    }

    return children;
}

bool AccessibilityHandler::isParentOf (const AccessibilityHandler* possibleChild) const noexcept
{
    while (possibleChild != nullptr)
    {
        possibleChild = possibleChild->getParent();

        if (possibleChild == this)
            return true;
    }

    return false;
}

AccessibilityHandler* AccessibilityHandler::getChildAt (Point<int> screenPoint)
{
    if (auto* comp = Desktop::getInstance().findComponentAt (screenPoint))
    {
        if (auto* handler = getUnignoredAncestor (findEnclosingHandler (comp)))
            if (isParentOf (handler))
                return handler;
    }

    return nullptr;
}

AccessibilityHandler* AccessibilityHandler::getChildFocus()
{
    return hasFocus (true) ? getUnignoredAncestor (currentlyFocusedHandler)
                           : nullptr;
}

bool AccessibilityHandler::hasFocus (bool trueIfChildFocused) const
{
    return currentlyFocusedHandler != nullptr
            && (currentlyFocusedHandler == this
                || (trueIfChildFocused && isParentOf (currentlyFocusedHandler)));
}

void AccessibilityHandler::grabFocus()
{
    if (! hasFocus (false))
        grabFocusInternal (true);
}

void AccessibilityHandler::giveAwayFocus() const
{
    if (hasFocus (true))
        giveAwayFocusInternal();
}

void AccessibilityHandler::grabFocusInternal (bool canTryParent)
{
    if (getCurrentState().isFocusable() && ! isIgnored())
    {
        takeFocus();
        return;
    }

    if (isParentOf (currentlyFocusedHandler))
        return;

    if (auto traverser = component.createFocusTraverser())
    {
        if (auto* defaultComp = traverser->getDefaultComponent (&component))
        {
            if (auto* handler = getUnignoredAncestor (findEnclosingHandler (defaultComp)))
            {
                if (isParentOf (handler))
                {
                    handler->grabFocusInternal (false);
                    return;
                }
            }
        }
    }

    if (canTryParent)
        if (auto* parent = getParent())
            parent->grabFocusInternal (true);
}

void AccessibilityHandler::giveAwayFocusInternal() const
{
    currentlyFocusedHandler = nullptr;
    notifyAccessibilityEventInternal (*this, InternalAccessibilityEvent::focusChanged);
}

void AccessibilityHandler::takeFocus()
{
    currentlyFocusedHandler = this;
    notifyAccessibilityEventInternal (*this, InternalAccessibilityEvent::focusChanged);

    if ((component.isShowing() || component.isOnDesktop())
        && component.getWantsKeyboardFocus()
        && ! component.hasKeyboardFocus (true))
    {
        component.grabKeyboardFocus();
    }
}

} // namespace juce