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

   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
{

class WindowsUIAWrapper  : public DeletedAtShutdown
{
public:
    bool isLoaded() const noexcept
    {
        return uiaReturnRawElementProvider            != nullptr
            && uiaHostProviderFromHwnd                != nullptr
            && uiaRaiseAutomationPropertyChangedEvent != nullptr
            && uiaRaiseAutomationEvent                != nullptr
            && uiaClientsAreListening                 != nullptr
            && uiaDisconnectProvider                  != nullptr
            && uiaDisconnectAllProviders              != nullptr;
    }

    //==============================================================================
    LRESULT returnRawElementProvider (HWND hwnd, WPARAM wParam, LPARAM lParam, IRawElementProviderSimple* provider)
    {
        return uiaReturnRawElementProvider != nullptr ? uiaReturnRawElementProvider (hwnd, wParam, lParam, provider)
                                                      : (LRESULT) nullptr;
    }

    JUCE_COMRESULT hostProviderFromHwnd (HWND hwnd, IRawElementProviderSimple** provider)
    {
        return uiaHostProviderFromHwnd != nullptr ? uiaHostProviderFromHwnd (hwnd, provider)
                                                  : (HRESULT) UIA_E_NOTSUPPORTED;
    }

    JUCE_COMRESULT raiseAutomationPropertyChangedEvent (IRawElementProviderSimple* provider, PROPERTYID propID, VARIANT oldValue, VARIANT newValue)
    {
        return uiaRaiseAutomationPropertyChangedEvent != nullptr ? uiaRaiseAutomationPropertyChangedEvent (provider, propID, oldValue, newValue)
                                                                 : (HRESULT) UIA_E_NOTSUPPORTED;
    }

    JUCE_COMRESULT raiseAutomationEvent (IRawElementProviderSimple* provider, EVENTID eventID)
    {
        return uiaRaiseAutomationEvent != nullptr ? uiaRaiseAutomationEvent (provider, eventID)
                                                  : (HRESULT) UIA_E_NOTSUPPORTED;
    }

    BOOL clientsAreListening()
    {
        return uiaClientsAreListening != nullptr ? uiaClientsAreListening()
                                                 : false;
    }

    JUCE_COMRESULT disconnectProvider (IRawElementProviderSimple* provider)
    {
        if (uiaDisconnectProvider != nullptr)
        {
            const ScopedValueSetter<IRawElementProviderSimple*> disconnectingProviderSetter (disconnectingProvider, provider);
            return uiaDisconnectProvider (provider);
        }

        return (HRESULT) UIA_E_NOTSUPPORTED;
    }

    JUCE_COMRESULT disconnectAllProviders()
    {
        if (uiaDisconnectAllProviders != nullptr)
        {
            const ScopedValueSetter<bool> disconnectingAllProvidersSetter (disconnectingAllProviders, true);
            return uiaDisconnectAllProviders();
        }

        return (HRESULT) UIA_E_NOTSUPPORTED;
    }

    //==============================================================================
    bool isProviderDisconnecting (IRawElementProviderSimple* provider)
    {
        return disconnectingProvider == provider || disconnectingAllProviders;
    }

    //==============================================================================
    JUCE_DECLARE_SINGLETON_SINGLETHREADED_MINIMAL (WindowsUIAWrapper)

private:
    //==============================================================================
    WindowsUIAWrapper()
    {
        // force UIA COM library initialisation here to prevent an exception when calling methods from SendMessage()
        if (isLoaded())
            returnRawElementProvider (nullptr, 0, 0, nullptr);
        else
            jassertfalse; // UIAutomationCore could not be loaded!
    }

    ~WindowsUIAWrapper()
    {
        disconnectAllProviders();

        if (uiaHandle != nullptr)
            ::FreeLibrary (uiaHandle);

        clearSingletonInstance();
    }

    //==============================================================================
    template <typename FuncType>
    static FuncType getUiaFunction (HMODULE module, LPCSTR funcName)
    {
        JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wcast-function-type")
        return (FuncType) GetProcAddress (module, funcName);
        JUCE_END_IGNORE_WARNINGS_GCC_LIKE
    }

    //==============================================================================
    using UiaReturnRawElementProviderFunc            = LRESULT (WINAPI*) (HWND, WPARAM, LPARAM, IRawElementProviderSimple*);
    using UiaHostProviderFromHwndFunc                = HRESULT (WINAPI*) (HWND, IRawElementProviderSimple**);
    using UiaRaiseAutomationPropertyChangedEventFunc = HRESULT (WINAPI*) (IRawElementProviderSimple*, PROPERTYID, VARIANT, VARIANT);
    using UiaRaiseAutomationEventFunc                = HRESULT (WINAPI*) (IRawElementProviderSimple*, EVENTID);
    using UiaClientsAreListeningFunc                 = BOOL    (WINAPI*) ();
    using UiaDisconnectProviderFunc                  = HRESULT (WINAPI*) (IRawElementProviderSimple*);
    using UiaDisconnectAllProvidersFunc              = HRESULT (WINAPI*) ();

    HMODULE uiaHandle = ::LoadLibraryA ("UIAutomationCore.dll");
    UiaReturnRawElementProviderFunc            uiaReturnRawElementProvider            = getUiaFunction<UiaReturnRawElementProviderFunc>            (uiaHandle, "UiaReturnRawElementProvider");
    UiaHostProviderFromHwndFunc                uiaHostProviderFromHwnd                = getUiaFunction<UiaHostProviderFromHwndFunc>                (uiaHandle, "UiaHostProviderFromHwnd");
    UiaRaiseAutomationPropertyChangedEventFunc uiaRaiseAutomationPropertyChangedEvent = getUiaFunction<UiaRaiseAutomationPropertyChangedEventFunc> (uiaHandle, "UiaRaiseAutomationPropertyChangedEvent");
    UiaRaiseAutomationEventFunc                uiaRaiseAutomationEvent                = getUiaFunction<UiaRaiseAutomationEventFunc>                (uiaHandle, "UiaRaiseAutomationEvent");
    UiaClientsAreListeningFunc                 uiaClientsAreListening                 = getUiaFunction<UiaClientsAreListeningFunc>                 (uiaHandle, "UiaClientsAreListening");
    UiaDisconnectProviderFunc                  uiaDisconnectProvider                  = getUiaFunction<UiaDisconnectProviderFunc>                  (uiaHandle, "UiaDisconnectProvider");
    UiaDisconnectAllProvidersFunc              uiaDisconnectAllProviders              = getUiaFunction<UiaDisconnectAllProvidersFunc>              (uiaHandle, "UiaDisconnectAllProviders");

    IRawElementProviderSimple* disconnectingProvider = nullptr;
    bool disconnectingAllProviders = false;

    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (WindowsUIAWrapper)
};

} // namespace juce