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

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

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   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
{

#if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

class WorkgroupToken::TokenProvider
{
public:
    explicit TokenProvider (os_workgroup_t wg)
        : workgroup (wg), attached (attach (wg, token)) {}

    ~TokenProvider()
    {
        if (attached)
            detach (workgroup, token);
    }

    TokenProvider (const TokenProvider&) = delete;
    TokenProvider (TokenProvider&& other) noexcept
        : workgroup (std::exchange (other.workgroup, os_workgroup_t{})),
          token (std::exchange (other.token, os_workgroup_join_token_s{})),
          attached (std::exchange (other.attached, false)) {}

    TokenProvider& operator= (const TokenProvider&) = delete;
    TokenProvider& operator= (TokenProvider&& other) noexcept
    {
        TokenProvider { std::move (other) }.swap (*this);
        return *this;
    }

    bool isAttached()             const { return attached; }
    os_workgroup_t getHandle()    const { return workgroup; }

private:
    static void detach (os_workgroup_t wg, os_workgroup_join_token_s token)
    {
        if (@available (macos 11.0, ios 14.0, *))
            os_workgroup_leave (wg, &token);
    }

    static bool attach (os_workgroup_t wg, os_workgroup_join_token_s& tokenOut)
    {
        if (@available (macos 11.0, ios 14.0, *))
        {
            if (wg != nullptr && os_workgroup_join (wg, &tokenOut) == 0)
                return true;
        }

        return false;
    }

    void swap (TokenProvider& other) noexcept
    {
        std::swap (other.workgroup, workgroup);
        std::swap (other.token, token);
        std::swap (other.attached, attached);
    }

    os_workgroup_t workgroup;
    os_workgroup_join_token_s token;
    bool attached;
};

class AudioWorkgroup::WorkgroupProvider
{
public:
    explicit WorkgroupProvider (os_workgroup_t ptr) : handle { ptr } {}

    void join (WorkgroupToken& token) const
    {
        if (const auto* tokenProvider = token.getTokenProvider())
            if (tokenProvider->isAttached() && tokenProvider->getHandle() == handle.get())
                return;

        // Explicit reset before constructing the new workgroup to ensure that the old workgroup
        // is left before the new one is joined.
        token.reset();

        if (handle.get() != nullptr)
            token = WorkgroupToken { [provider = WorkgroupToken::TokenProvider { handle.get() }] { return &provider; } };
    }

    static os_workgroup_t getWorkgroup (const AudioWorkgroup& wg)
    {
        if (auto* provider = wg.getWorkgroupProvider())
            return provider->handle.get();

        return nullptr;
    }

private:
    struct ScopedWorkgroupRetainer
    {
        ScopedWorkgroupRetainer (os_workgroup_t wg) : handle { wg }
        {
            if (handle != nullptr)
                os_retain (handle);
        }

        ~ScopedWorkgroupRetainer()
        {
            if (handle != nullptr)
                os_release (handle);
        }

        ScopedWorkgroupRetainer (const ScopedWorkgroupRetainer& other)
            : ScopedWorkgroupRetainer { other.handle } {}

        ScopedWorkgroupRetainer& operator= (const ScopedWorkgroupRetainer& other)
        {
            ScopedWorkgroupRetainer { other }.swap (*this);
            return *this;
        }

        ScopedWorkgroupRetainer (ScopedWorkgroupRetainer&& other) noexcept
        {
            swap (other);
        }

        ScopedWorkgroupRetainer& operator= (ScopedWorkgroupRetainer&& other) noexcept
        {
            swap (other);
            return *this;
        }

        void swap (ScopedWorkgroupRetainer& other) noexcept
        {
            std::swap (handle, other.handle);
        }

        os_workgroup_t get() const noexcept { return handle; }

    private:
        os_workgroup_t handle { nullptr };
    };

    ScopedWorkgroupRetainer handle;
};

#else

class WorkgroupToken::TokenProvider {};

class AudioWorkgroup::WorkgroupProvider
{
public:
    explicit WorkgroupProvider() = default;

    void join (WorkgroupToken& t) const { t.reset(); }

    static void* getWorkgroup (const AudioWorkgroup&) { return nullptr; }
};

#endif

AudioWorkgroup::AudioWorkgroup (const AudioWorkgroup& other)
    : erased ([&]() -> Erased
              {
                  if (auto* p = other.getWorkgroupProvider())
                      return [provider = *p] { return &provider; };

                  return nullptr;
              }()) {}

bool AudioWorkgroup::operator== (const AudioWorkgroup& other) const
{
    return WorkgroupProvider::getWorkgroup (*this) == WorkgroupProvider::getWorkgroup (other);
}

void AudioWorkgroup::join (WorkgroupToken& token) const
{
   #if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

    if (const auto* p = getWorkgroupProvider())
    {
        p->join (token);
        return;
    }

   #endif

    token.reset();
}

size_t AudioWorkgroup::getMaxParallelThreadCount() const
{
   #if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

    if (@available (macos 11.0, ios 14.0, *))
    {
        if (auto wg = WorkgroupProvider::getWorkgroup (*this))
            return (size_t) os_workgroup_max_parallel_threads (wg, nullptr);
    }

   #endif

   return 0;
}

AudioWorkgroup::operator bool() const { return WorkgroupProvider::getWorkgroup (*this) != nullptr; }

#if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

AudioWorkgroup makeRealAudioWorkgroup (os_workgroup_t handle)
{
    if (handle == nullptr)
        return AudioWorkgroup{};

    return AudioWorkgroup { [provider = AudioWorkgroup::WorkgroupProvider { handle }] { return &provider; } };
}

#endif

} // namespace juce