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

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2017 - ROLI Ltd.

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   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
{

static int getAllowedTextureSize (int x)
{
   #if JUCE_OPENGL_ALLOW_NON_POWER_OF_TWO_TEXTURES
    return x;
   #else
    return nextPowerOfTwo (x);
   #endif
}

OpenGLTexture::OpenGLTexture()
    : textureID (0), width (0), height (0), ownerContext (nullptr)
{
}

OpenGLTexture::~OpenGLTexture()
{
    release();
}

bool OpenGLTexture::isValidSize (int width, int height)
{
    return isPowerOfTwo (width) && isPowerOfTwo (height);
}

void OpenGLTexture::create (const int w, const int h, const void* pixels, GLenum type, bool topLeft)
{
    ownerContext = OpenGLContext::getCurrentContext();

    // Texture objects can only be created when the current thread has an active OpenGL
    // context. You'll need to create this object in one of the OpenGLContext's callbacks.
    jassert (ownerContext != nullptr);

    if (textureID == 0)
    {
        JUCE_CHECK_OPENGL_ERROR
        glGenTextures (1, &textureID);
        glBindTexture (GL_TEXTURE_2D, textureID);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

        auto glMagFilter = (ownerContext->texMagFilter == OpenGLContext::linear ? GL_LINEAR : GL_NEAREST);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, glMagFilter);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        JUCE_CHECK_OPENGL_ERROR
    }
    else
    {
        glBindTexture (GL_TEXTURE_2D, textureID);
        JUCE_CHECK_OPENGL_ERROR;
    }

    glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
    JUCE_CHECK_OPENGL_ERROR

    width  = getAllowedTextureSize (w);
    height = getAllowedTextureSize (h);

    const GLint internalformat = type == GL_ALPHA ? GL_ALPHA : GL_RGBA;

    if (width != w || height != h)
    {
        glTexImage2D (GL_TEXTURE_2D, 0, internalformat,
                      width, height, 0, type, GL_UNSIGNED_BYTE, nullptr);

        glTexSubImage2D (GL_TEXTURE_2D, 0, 0, topLeft ? (height - h) : 0, w, h,
                         type, GL_UNSIGNED_BYTE, pixels);
    }
    else
    {
        glTexImage2D (GL_TEXTURE_2D, 0, internalformat,
                      w, h, 0, type, GL_UNSIGNED_BYTE, pixels);
    }

    JUCE_CHECK_OPENGL_ERROR
}

template <class PixelType>
struct Flipper
{
    static void flip (HeapBlock<PixelARGB>& dataCopy, const uint8* srcData, const int lineStride,
                      const int w, const int h)
    {
        dataCopy.malloc (w * h);

        for (int y = 0; y < h; ++y)
        {
            auto* src = (const PixelType*) srcData;
            auto* dst = (PixelARGB*) (dataCopy + w * (h - 1 - y));

            for (int x = 0; x < w; ++x)
                dst[x].set (src[x]);

            srcData += lineStride;
        }
    }
};

void OpenGLTexture::loadImage (const Image& image)
{
    const int imageW = image.getWidth();
    const int imageH = image.getHeight();

    HeapBlock<PixelARGB> dataCopy;
    Image::BitmapData srcData (image, Image::BitmapData::readOnly);

    switch (srcData.pixelFormat)
    {
        case Image::ARGB:           Flipper<PixelARGB> ::flip (dataCopy, srcData.data, srcData.lineStride, imageW, imageH); break;
        case Image::RGB:            Flipper<PixelRGB>  ::flip (dataCopy, srcData.data, srcData.lineStride, imageW, imageH); break;
        case Image::SingleChannel:  Flipper<PixelAlpha>::flip (dataCopy, srcData.data, srcData.lineStride, imageW, imageH); break;
        case Image::UnknownFormat:
        default: break;
    }

    create (imageW, imageH, dataCopy, JUCE_RGBA_FORMAT, true);
}

void OpenGLTexture::loadARGB (const PixelARGB* pixels, const int w, const int h)
{
    create (w, h, pixels, JUCE_RGBA_FORMAT, false);
}

void OpenGLTexture::loadAlpha (const uint8* pixels, int w, int h)
{
    create (w, h, pixels, GL_ALPHA, false);
}

void OpenGLTexture::loadARGBFlipped (const PixelARGB* pixels, int w, int h)
{
    HeapBlock<PixelARGB> flippedCopy;
    Flipper<PixelARGB>::flip (flippedCopy, (const uint8*) pixels, 4 * w, w, h);

    create (w, h, flippedCopy, JUCE_RGBA_FORMAT, true);
}

void OpenGLTexture::release()
{
    if (textureID != 0)
    {
        // If the texture is deleted while the owner context is not active, it's
        // impossible to delete it, so this will be a leak until the context itself
        // is deleted.
        jassert (ownerContext == OpenGLContext::getCurrentContext());

        if (ownerContext == OpenGLContext::getCurrentContext())
        {
            glDeleteTextures (1, &textureID);

            textureID = 0;
            width = 0;
            height = 0;
        }
    }
}

void OpenGLTexture::bind() const
{
    glBindTexture (GL_TEXTURE_2D, textureID);
}

void OpenGLTexture::unbind() const
{
    glBindTexture (GL_TEXTURE_2D, 0);
}

} // namespace juce