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

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

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

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

namespace juce
{

namespace DragAndDropHelpers
{
    //==============================================================================
    struct JuceDropSource final : public ComBaseClassHelper<IDropSource>
    {
        JuceDropSource() = default;

        JUCE_COMRESULT QueryContinueDrag (BOOL escapePressed, DWORD keys) override
        {
            if (escapePressed)
                return DRAGDROP_S_CANCEL;

            if ((keys & (MK_LBUTTON | MK_RBUTTON)) == 0)
                return DRAGDROP_S_DROP;

            return S_OK;
        }

        JUCE_COMRESULT GiveFeedback (DWORD) override
        {
            return DRAGDROP_S_USEDEFAULTCURSORS;
        }
    };

    //==============================================================================
    struct JuceEnumFormatEtc final : public ComBaseClassHelper<IEnumFORMATETC>
    {
        JuceEnumFormatEtc (const FORMATETC* f)  : format (f) {}

        JUCE_COMRESULT Clone (IEnumFORMATETC** result) override
        {
            if (result == nullptr)
                return E_POINTER;

            auto newOne = new JuceEnumFormatEtc (format);
            newOne->index = index;
            *result = newOne;
            return S_OK;
        }

        JUCE_COMRESULT Next (ULONG celt, LPFORMATETC lpFormatEtc, ULONG* pceltFetched) override
        {
            if (pceltFetched != nullptr)
                *pceltFetched = 0;
            else if (celt != 1)
                return S_FALSE;

            if (index == 0 && celt > 0 && lpFormatEtc != nullptr)
            {
                copyFormatEtc (lpFormatEtc [0], *format);
                ++index;

                if (pceltFetched != nullptr)
                    *pceltFetched = 1;

                return S_OK;
            }

            return S_FALSE;
        }

        JUCE_COMRESULT Skip (ULONG celt) override
        {
            if (index + (int) celt >= 1)
                return S_FALSE;

            index += (int) celt;
            return S_OK;
        }

        JUCE_COMRESULT Reset() override
        {
            index = 0;
            return S_OK;
        }

    private:
        const FORMATETC* const format;
        int index = 0;

        static void copyFormatEtc (FORMATETC& dest, const FORMATETC& source)
        {
            dest = source;

            if (source.ptd != nullptr)
            {
                dest.ptd = (DVTARGETDEVICE*) CoTaskMemAlloc (sizeof (DVTARGETDEVICE));

                if (dest.ptd != nullptr)
                    *(dest.ptd) = *(source.ptd);
            }
        }

        JUCE_DECLARE_NON_COPYABLE (JuceEnumFormatEtc)
    };

    //==============================================================================
    class JuceDataObject final : public ComBaseClassHelper<IDataObject>
    {
    public:
        JuceDataObject (const FORMATETC* f, const STGMEDIUM* m)
            : format (f), medium (m)
        {
        }

        ~JuceDataObject() override
        {
            jassert (refCount == 0);
        }

        JUCE_COMRESULT GetData (FORMATETC* pFormatEtc, STGMEDIUM* pMedium) override
        {
            if ((pFormatEtc->tymed & format->tymed) != 0
                 && pFormatEtc->cfFormat == format->cfFormat
                 && pFormatEtc->dwAspect == format->dwAspect)
            {
                pMedium->tymed = format->tymed;
                pMedium->pUnkForRelease = nullptr;

                if (format->tymed == TYMED_HGLOBAL)
                {
                    auto len = GlobalSize (medium->hGlobal);
                    void* const src = GlobalLock (medium->hGlobal);
                    void* const dst = GlobalAlloc (GMEM_FIXED, len);

                    if (src != nullptr && dst != nullptr)
                        memcpy (dst, src, len);

                    GlobalUnlock (medium->hGlobal);

                    pMedium->hGlobal = dst;
                    return S_OK;
                }
            }

            return DV_E_FORMATETC;
        }

        JUCE_COMRESULT QueryGetData (FORMATETC* f) override
        {
            if (f == nullptr)
                return E_INVALIDARG;

            if (f->tymed == format->tymed
                  && f->cfFormat == format->cfFormat
                  && f->dwAspect == format->dwAspect)
                return S_OK;

            return DV_E_FORMATETC;
        }

        JUCE_COMRESULT GetCanonicalFormatEtc (FORMATETC*, FORMATETC* pFormatEtcOut) override
        {
            pFormatEtcOut->ptd = nullptr;
            return E_NOTIMPL;
        }

        JUCE_COMRESULT EnumFormatEtc (DWORD direction, IEnumFORMATETC** result) override
        {
            if (result == nullptr)
                return E_POINTER;

            if (direction == DATADIR_GET)
            {
                *result = new JuceEnumFormatEtc (format);
                return S_OK;
            }

            *result = nullptr;
            return E_NOTIMPL;
        }

        JUCE_COMRESULT GetDataHere (FORMATETC*, STGMEDIUM*)                  override { return DATA_E_FORMATETC; }
        JUCE_COMRESULT SetData (FORMATETC*, STGMEDIUM*, BOOL)                override { return E_NOTIMPL; }
        JUCE_COMRESULT DAdvise (FORMATETC*, DWORD, IAdviseSink*, DWORD*)     override { return OLE_E_ADVISENOTSUPPORTED; }
        JUCE_COMRESULT DUnadvise (DWORD)                                     override { return E_NOTIMPL; }
        JUCE_COMRESULT EnumDAdvise (IEnumSTATDATA**)                         override { return OLE_E_ADVISENOTSUPPORTED; }

    private:
        const FORMATETC* const format;
        const STGMEDIUM* const medium;

        JUCE_DECLARE_NON_COPYABLE (JuceDataObject)
    };

    //==============================================================================
    static HDROP createHDrop (const StringArray& fileNames)
    {
        size_t totalBytes = 0;
        for (int i = fileNames.size(); --i >= 0;)
            totalBytes += CharPointer_UTF16::getBytesRequiredFor (fileNames[i].getCharPointer()) + sizeof (WCHAR);

        struct Deleter
        {
            void operator() (void* ptr) const noexcept { GlobalFree (ptr); }
        };

        auto hDrop = std::unique_ptr<void, Deleter> ((HDROP) GlobalAlloc (GMEM_MOVEABLE | GMEM_ZEROINIT, sizeof (DROPFILES) + totalBytes + 4));

        if (hDrop != nullptr)
        {
            auto pDropFiles = (LPDROPFILES) GlobalLock (hDrop.get());

            if (pDropFiles == nullptr)
                return nullptr;

            pDropFiles->pFiles = sizeof (DROPFILES);
            pDropFiles->fWide = true;

            auto* fname = reinterpret_cast<WCHAR*> (addBytesToPointer (pDropFiles, sizeof (DROPFILES)));

            for (int i = 0; i < fileNames.size(); ++i)
            {
                auto bytesWritten = fileNames[i].copyToUTF16 (fname, 2048);
                fname = reinterpret_cast<WCHAR*> (addBytesToPointer (fname, bytesWritten));
            }

            *fname = 0;

            GlobalUnlock (hDrop.get());
        }

        return static_cast<HDROP> (hDrop.release());
    }

    struct DragAndDropJob final : public ThreadPoolJob
    {
        DragAndDropJob (FORMATETC f, STGMEDIUM m, DWORD d, std::function<void()>&& cb)
            : ThreadPoolJob ("DragAndDrop"),
              format (f), medium (m), whatToDo (d),
              completionCallback (std::move (cb))
        {
        }

        JobStatus runJob() override
        {
            [[maybe_unused]] const auto result = OleInitialize (nullptr);

            auto* source = new JuceDropSource();
            auto* data = new JuceDataObject (&format, &medium);

            DWORD effect;
            DoDragDrop (data, source, whatToDo, &effect);

            data->Release();
            source->Release();

            OleUninitialize();

            if (completionCallback != nullptr)
                MessageManager::callAsync (std::move (completionCallback));

            return jobHasFinished;
        }

        FORMATETC format;
        STGMEDIUM medium;
        DWORD whatToDo;

        std::function<void()> completionCallback;
    };

    class ThreadPoolHolder final : private DeletedAtShutdown
    {
    public:
        ThreadPoolHolder() = default;

        ~ThreadPoolHolder()
        {
            // Wait forever if there's a job running. The user needs to cancel the transfer
            // in the GUI.
            pool.removeAllJobs (true, -1);

            clearSingletonInstance();
        }

        JUCE_DECLARE_SINGLETON_SINGLETHREADED (ThreadPoolHolder, false)

        // We need to make sure we don't do simultaneous text and file drag and drops,
        // so use a pool that can only run a single job.
        ThreadPool pool { ThreadPoolOptions{}.withNumberOfThreads (1) };
    };

    JUCE_IMPLEMENT_SINGLETON (ThreadPoolHolder)
}

//==============================================================================
bool DragAndDropContainer::performExternalDragDropOfFiles (const StringArray& files, const bool canMove,
                                                           Component*, std::function<void()> callback)
{
    if (files.isEmpty())
        return false;

    FORMATETC format = { CF_HDROP, nullptr, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
    STGMEDIUM medium = { TYMED_HGLOBAL, { nullptr }, nullptr };

    medium.hGlobal = DragAndDropHelpers::createHDrop (files);

    auto& pool = DragAndDropHelpers::ThreadPoolHolder::getInstance()->pool;
    pool.addJob (new DragAndDropHelpers::DragAndDropJob (format, medium,
                                                         canMove ? (DROPEFFECT_COPY | DROPEFFECT_MOVE) : DROPEFFECT_COPY,
                                                         std::move (callback)),
                true);

    return true;
}

bool DragAndDropContainer::performExternalDragDropOfText (const String& text, Component*, std::function<void()> callback)
{
    if (text.isEmpty())
        return false;

    FORMATETC format = { CF_TEXT, nullptr, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
    STGMEDIUM medium = { TYMED_HGLOBAL, { nullptr }, nullptr };

    auto numBytes = CharPointer_UTF16::getBytesRequiredFor (text.getCharPointer());

    medium.hGlobal = GlobalAlloc (GMEM_MOVEABLE | GMEM_ZEROINIT, numBytes + 2);

    if (medium.hGlobal == nullptr)
        return false;

    auto* data = static_cast<WCHAR*> (GlobalLock (medium.hGlobal));

    text.copyToUTF16 (data, numBytes + 2);
    format.cfFormat = CF_UNICODETEXT;

    GlobalUnlock (medium.hGlobal);

    auto& pool = DragAndDropHelpers::ThreadPoolHolder::getInstance()->pool;
    pool.addJob (new DragAndDropHelpers::DragAndDropJob (format,
                                                        medium,
                                                        DROPEFFECT_COPY | DROPEFFECT_MOVE,
                                                        std::move (callback)),
                 true);

    return true;
}

} // namespace juce
