#include "XCEngine/RHI/OpenGL/OpenGLFence.h"
#include <glad/glad.h>

namespace XCEngine {
namespace RHI {

OpenGLFence::OpenGLFence()
    : m_sync(nullptr)
    , m_signaledValue(0)
    , m_completedValue(0) {
}

OpenGLFence::~OpenGLFence() {
    Shutdown();
}

bool OpenGLFence::Initialize(uint64_t initialValue) {
    m_signaledValue.store(initialValue, std::memory_order_release);
    m_completedValue.store(initialValue, std::memory_order_release);
    return true;
}

void OpenGLFence::Shutdown() {
    if (m_sync) {
        glDeleteSync(static_cast<GLsync>(m_sync));
        m_sync = nullptr;
    }
    m_signaledValue.store(0, std::memory_order_release);
    m_completedValue.store(0, std::memory_order_release);
}

void OpenGLFence::Signal() {
    Signal(1);
}

void OpenGLFence::Signal(uint64_t value) {
    if (m_sync) {
        glClientWaitSync(static_cast<GLsync>(m_sync), GL_SYNC_FLUSH_COMMANDS_BIT, GL_TIMEOUT_IGNORED);
        glDeleteSync(static_cast<GLsync>(m_sync));
        m_sync = nullptr;
    }

    glFlush();

    m_signaledValue.store(value, std::memory_order_release);
    m_sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
}

void OpenGLFence::Wait(uint64_t value) {
    uint64_t currentCompleted = m_completedValue.load(std::memory_order_acquire);
    if (currentCompleted >= value) {
        return;
    }

    if (m_sync) {
        glClientWaitSync(static_cast<GLsync>(m_sync), GL_SYNC_FLUSH_COMMANDS_BIT, GL_TIMEOUT_IGNORED);
        glDeleteSync(static_cast<GLsync>(m_sync));
        m_sync = nullptr;
    }

    uint64_t signaled = m_signaledValue.load(std::memory_order_acquire);
    m_completedValue.store(signaled, std::memory_order_release);
}

uint64_t OpenGLFence::GetCompletedValue() const {
    if (!m_sync) {
        return m_completedValue.load(std::memory_order_acquire);
    }

    GLint status = 0;
    glGetSynciv(static_cast<GLsync>(m_sync), GL_SYNC_STATUS, sizeof(status), nullptr, &status);

    if (status == GL_SIGNALED) {
        return m_signaledValue.load(std::memory_order_acquire);
    }

    return m_completedValue.load(std::memory_order_acquire);
}

void* OpenGLFence::GetNativeHandle() {
    if (!m_sync) {
        m_sync = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
    }
    return m_sync;
}

} // namespace RHI
} // namespace XCEngine