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

namespace XCEngine {
namespace RHI {

OpenGLFence::OpenGLFence() 
    : m_sync(nullptr)
    , m_fenceValue(0)
    , m_completedValue(0)
    , m_signaled(false) {
}

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

bool OpenGLFence::Initialize(bool signaled) {
    m_fenceValue = signaled ? 1 : 0;
    m_completedValue = m_fenceValue;
    m_signaled = signaled;
    return true;
}

void OpenGLFence::Shutdown() {
    if (m_sync) {
        glDeleteSync(static_cast<GLsync>(m_sync));
        m_sync = nullptr;
    }
}

void OpenGLFence::Signal() {
    glFlush();
    m_fenceValue++;
    m_signaled = true;
}

void OpenGLFence::Signal(uint64_t value) {
    glFlush();
    m_fenceValue = value;
    m_signaled = true;
}

void OpenGLFence::Wait(uint64_t timeoutNs) {
    if (!m_signaled || !m_sync) {
        glFinish();
        m_completedValue = m_fenceValue;
        m_signaled = true;
        return;
    }

    GLsync sync = static_cast<GLsync>(m_sync);
    GLenum result = glClientWaitSync(sync, GL_SYNC_FLUSH_COMMANDS_BIT, timeoutNs);
    while (result == GL_TIMEOUT_EXPIRED && timeoutNs > 0) {
        result = glClientWaitSync(sync, 0, timeoutNs);
    }

    if (result == GL_ALREADY_SIGNALED || result == GL_CONDITION_SATISFIED) {
        m_completedValue = m_fenceValue;
    }
}

void OpenGLFence::Reset() {
    if (m_sync) {
        glDeleteSync(static_cast<GLsync>(m_sync));
        m_sync = nullptr;
    }
    m_signaled = false;
}

bool OpenGLFence::IsSignaled() const {
    return m_signaled;
}

FenceStatus OpenGLFence::GetStatus() const {
    if (!m_sync) {
        return m_signaled ? FenceStatus::Signaled : FenceStatus::Unsignaled;
    }

    GLsync sync = static_cast<GLsync>(m_sync);
    GLint status = 0;
    glGetSynciv(sync, GL_SYNC_STATUS, sizeof(status), nullptr, &status);
    
    if (status == GL_SIGNALED) {
        return FenceStatus::Signaled;
    }
    return FenceStatus::Unsignaled;
}

uint64_t OpenGLFence::GetCompletedValue() const {
    return m_completedValue;
}

} // namespace RHI
} // namespace XCEngine