#include "XCEngine/RHI/OpenGL/OpenGLTextureUnitAllocator.h"
#include "XCEngine/RHI/OpenGL/OpenGLTexture.h"

#include <glad/glad.h>

namespace XCEngine {
namespace RHI {

OpenGLTextureUnitAllocator::OpenGLTextureUnitAllocator()
    : m_maxUnits(0) {
}

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

void OpenGLTextureUnitAllocator::Initialize(uint32_t maxUnits) {
    m_maxUnits = maxUnits;
    m_allocated.resize(maxUnits, false);
    m_boundTextures.resize(maxUnits, nullptr);
}

void OpenGLTextureUnitAllocator::Shutdown() {
    for (uint32_t i = 0; i < m_maxUnits; ++i) {
        if (m_allocated[i]) {
            Free(static_cast<int32_t>(i));
        }
    }
    m_allocated.clear();
    m_boundTextures.clear();
    m_maxUnits = 0;
}

int32_t OpenGLTextureUnitAllocator::Allocate() {
    for (uint32_t i = 0; i < m_maxUnits; ++i) {
        if (!m_allocated[i]) {
            m_allocated[i] = true;
            return static_cast<int32_t>(i);
        }
    }
    return -1;
}

void OpenGLTextureUnitAllocator::Free(int32_t unit) {
    if (unit < 0 || unit >= static_cast<int32_t>(m_maxUnits)) {
        return;
    }
    UnbindTexture(unit);
    m_allocated[unit] = false;
}

void OpenGLTextureUnitAllocator::BindTexture(int32_t unit, OpenGLTexture* texture) {
    if (unit < 0 || unit >= static_cast<int32_t>(m_maxUnits)) {
        return;
    }
    glActiveTexture(GL_TEXTURE0 + unit);
    if (texture) {
        glBindTexture(static_cast<GLenum>(texture->GetOpenGLType()), texture->GetID());
    } else {
        glBindTexture(GL_TEXTURE_2D, 0);
    }
    m_boundTextures[unit] = texture;
}

void OpenGLTextureUnitAllocator::UnbindTexture(int32_t unit) {
    if (unit < 0 || unit >= static_cast<int32_t>(m_maxUnits)) {
        return;
    }
    glActiveTexture(GL_TEXTURE0 + unit);
    glBindTexture(GL_TEXTURE_2D, 0);
    m_boundTextures[unit] = nullptr;
}

OpenGLTexture* OpenGLTextureUnitAllocator::GetBoundTexture(int32_t unit) const {
    if (unit < 0 || unit >= static_cast<int32_t>(m_maxUnits)) {
        return nullptr;
    }
    return m_boundTextures[unit];
}

bool OpenGLTextureUnitAllocator::IsAllocated(int32_t unit) const {
    if (unit < 0 || unit >= static_cast<int32_t>(m_maxUnits)) {
        return false;
    }
    return m_allocated[unit];
}

} // namespace RHI
} // namespace XCEngine