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

   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
{

//==============================================================================
struct AccessibleObjCClassDeleter
{
    template <typename ElementType>
    void operator() (ElementType* element) const
    {
        juceFreeAccessibilityPlatformSpecificData (element);

        object_setInstanceVariable (element, "handler", nullptr);
        [element release];
    }
};

template <typename Base>
class AccessibleObjCClass  : public ObjCClass<Base>
{
public:
    using Holder = std::unique_ptr<Base, AccessibleObjCClassDeleter>;

protected:
    AccessibleObjCClass()  : ObjCClass<Base> ("JUCEAccessibilityElement_")
    {
        ObjCClass<Base>::template addIvar<AccessibilityHandler*> ("handler");
    }

    //==============================================================================
    static AccessibilityHandler* getHandler (id self)
    {
        return getIvar<AccessibilityHandler*> (self, "handler");
    }

    template <typename MemberFn>
    static auto getInterface (id self, MemberFn fn) noexcept -> decltype ((std::declval<AccessibilityHandler>().*fn)())
    {
        if (auto* handler = getHandler (self))
            return (handler->*fn)();

        return nullptr;
    }

    static AccessibilityTextInterface*  getTextInterface  (id self) noexcept  { return getInterface (self, &AccessibilityHandler::getTextInterface); }
    static AccessibilityValueInterface* getValueInterface (id self) noexcept  { return getInterface (self, &AccessibilityHandler::getValueInterface); }
    static AccessibilityTableInterface* getTableInterface (id self) noexcept  { return getInterface (self, &AccessibilityHandler::getTableInterface); }
    static AccessibilityCellInterface*  getCellInterface  (id self) noexcept  { return getInterface (self, &AccessibilityHandler::getCellInterface); }

    template <typename MemberFn>
    static auto getEnclosingInterface (AccessibilityHandler* handler, MemberFn fn) noexcept -> decltype ((std::declval<AccessibilityHandler>().*fn)())
    {
        if (handler == nullptr)
            return nullptr;

        if (auto* interface = (handler->*fn)())
            return interface;

        return getEnclosingInterface (handler->getParent(), fn);
    }

    static bool hasEditableText (AccessibilityHandler& handler) noexcept
    {
        return handler.getRole() == AccessibilityRole::editableText
            && handler.getTextInterface() != nullptr
            && ! handler.getTextInterface()->isReadOnly();
    }

    static id getAccessibilityValueFromInterfaces (const AccessibilityHandler& handler)
    {
        if (auto* textInterface = handler.getTextInterface())
            return juceStringToNS (textInterface->getText ({ 0, textInterface->getTotalNumCharacters() }));

        if (auto* valueInterface = handler.getValueInterface())
            return juceStringToNS (valueInterface->getCurrentValueAsString());

        return nil;
    }

    //==============================================================================
    static BOOL getIsAccessibilityElement (id self, SEL)
    {
        if (auto* handler = getHandler (self))
            return ! handler->isIgnored()
                  && handler->getRole() != AccessibilityRole::window;

        return NO;
    }

    static void setAccessibilityValue (id self, SEL, NSString* value)
    {
        if (auto* handler = getHandler (self))
        {
            if (hasEditableText (*handler))
            {
                handler->getTextInterface()->setText (nsStringToJuce (value));
                return;
            }

            if (auto* valueInterface = handler->getValueInterface())
                if (! valueInterface->isReadOnly())
                    valueInterface->setValueAsString (nsStringToJuce (value));
        }
    }

    static BOOL performActionIfSupported (id self, AccessibilityActionType actionType)
    {
        if (auto* handler = getHandler (self))
            if (handler->getActions().invoke (actionType))
                return YES;

        return NO;
    }

    static BOOL accessibilityPerformPress (id self, SEL)
    {
        if (auto* handler = getHandler (self))
            if (handler->getCurrentState().isCheckable() && handler->getActions().invoke (AccessibilityActionType::toggle))
                return YES;

        return performActionIfSupported (self, AccessibilityActionType::press);
    }

    static BOOL accessibilityPerformIncrement (id self, SEL)
    {
        if (auto* valueInterface = getValueInterface (self))
        {
            if (! valueInterface->isReadOnly())
            {
                auto range = valueInterface->getRange();

                if (range.isValid())
                {
                    valueInterface->setValue (jlimit (range.getMinimumValue(),
                                                      range.getMaximumValue(),
                                                      valueInterface->getCurrentValue() + range.getInterval()));
                    return YES;
                }
            }
        }

        return NO;
    }

    static BOOL accessibilityPerformDecrement (id self, SEL)
    {
        if (auto* valueInterface = getValueInterface (self))
        {
            if (! valueInterface->isReadOnly())
            {
                auto range = valueInterface->getRange();

                if (range.isValid())
                {
                    valueInterface->setValue (jlimit (range.getMinimumValue(),
                                                      range.getMaximumValue(),
                                                      valueInterface->getCurrentValue() - range.getInterval()));
                    return YES;
                }
            }
        }

        return NO;
    }

    static NSString* getAccessibilityTitle (id self, SEL)
    {
        if (auto* handler = getHandler (self))
        {
            auto title = handler->getTitle();

            if (title.isEmpty() && handler->getComponent().isOnDesktop())
                title = getAccessibleApplicationOrPluginName();

            NSString* nsString = juceStringToNS (title);

           #if ! JUCE_IOS
            if (nsString != nil && [[self accessibilityValue] isEqual: nsString])
                return @"";
           #endif

            return nsString;
        }

        return nil;
    }

    static NSString* getAccessibilityHelp (id self, SEL)
    {
        if (auto* handler = getHandler (self))
            return juceStringToNS (handler->getHelp());

        return nil;
    }

    static BOOL getIsAccessibilityModal (id self, SEL)
    {
        if (auto* handler = getHandler (self))
            return handler->getComponent().isCurrentlyModal();

        return NO;
    }

    static NSInteger getAccessibilityRowCount (id self, SEL)
    {
        if (auto* tableInterface = getTableInterface (self))
            return tableInterface->getNumRows();

        return 0;
    }

    static NSInteger getAccessibilityColumnCount (id self, SEL)
    {
        if (auto* tableInterface = getTableInterface (self))
            return tableInterface->getNumColumns();

        return 0;
    }

    static NSRange getAccessibilityRowIndexRange (id self, SEL)
    {
        if (auto* cellInterface = getCellInterface (self))
            return NSMakeRange ((NSUInteger) cellInterface->getRowIndex(),
                                (NSUInteger) cellInterface->getRowSpan());

        return NSMakeRange (0, 0);
    }

    static NSRange getAccessibilityColumnIndexRange (id self, SEL)
    {
        if (auto* cellInterface = getCellInterface (self))
            return NSMakeRange ((NSUInteger) cellInterface->getColumnIndex(),
                                (NSUInteger) cellInterface->getColumnSpan());

        return NSMakeRange (0, 0);
    }

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AccessibleObjCClass)
};

}