//
// SPDX-License-Identifier: BSD-3-Clause
// Copyright (c) Contributors to the OpenEXR Project.
//

#ifndef _PxDeepBaseHelper_h_
#define _PxDeepBaseHelper_h_

#include "PxDeepOutPixel.h"
#include "PxDeepOutRow.h"
#include "PxDeepUtils.h"

#include <dtex.h>

#include <ImfChannelList.h>
#include <ImfDeepScanLineOutputFile.h>
#include <ImfPartType.h>

#include <ImathBox.h>
#include <ImathVec.h>

namespace PxDeep
{

//-*****************************************************************************
// PARAMETERS STRUCT
//-*****************************************************************************
// This allows us to keep function signatures from changing around too much
// as the parameter set grows & changes, which it always does.
struct Parameters
{
    Parameters ()
        : deepOpacity (true)
        , discrete (true)
        , multiplyColorByAlpha (false)
        , sideways (false)
        , discardZeroAlphaSamples (true)
        , doDeepBack (true)
        , doRGB (true)
        , compressionError (0.0f)
    {}

    bool  deepOpacity;
    bool  discrete;
    bool  multiplyColorByAlpha;
    bool  sideways;
    bool  discardZeroAlphaSamples;
    bool  doDeepBack;
    bool  doRGB;
    float compressionError;
};

//-*****************************************************************************
// BASE DEEP HELPER CLASS
//-*****************************************************************************
// The intention of this templated base class is to provide consistent
// storage vectors for spans and deep pixels across multiple pixel reads,
// so we don't slow down constantly creating and destroying std::vectors.
// This class has a "processDeepBox" function which does the work.
template <typename RGBA_T, typename DERIVED, typename SPAN> class BaseDeepHelper
{
public:
    typedef DERIVED sub_type;
    typedef SPAN    span_type;

    BaseDeepHelper (
        DtexFile* i_dtexFile, int i_numDtexChans, const Parameters& i_params)
        : m_dtexFile (i_dtexFile)
        , m_numDtexChans (i_numDtexChans)
        , m_params (i_params)
    {
        m_image = NULL;
        DtexGetImageByIndex (m_dtexFile, 0, &m_image);

        m_fileWidth  = DtexWidth (m_image);
        m_fileHeight = DtexHeight (m_image);

        m_pixel    = DtexMakePixel (m_numDtexChans);
        m_rawPixel = DtexMakePixel (m_numDtexChans);
    }

    ~BaseDeepHelper ()
    {
        DtexDestroyPixel (m_pixel);
        DtexDestroyPixel (m_rawPixel);
    }

    void processDeepBox (
        Imf::DeepScanLineOutputFile& o_file, const Imath::Box2i& i_box);

protected:
    DtexFile*  m_dtexFile;
    int        m_numDtexChans;
    Parameters m_params;

    DtexImage* m_image;
    int        m_fileWidth;
    int        m_fileHeight;
    DtexPixel* m_pixel;
    DtexPixel* m_rawPixel;

    std::vector<span_type> m_spans;
    DeepOutPixel<RGBA_T>   m_deepOutPixel;
};

//-*****************************************************************************
//-*****************************************************************************
// SPAN CLASSES
//-*****************************************************************************
//-*****************************************************************************

//-*****************************************************************************
// These span objects are used by the helper classes below to keep track
// of the information read out of the DTEX file, so it can be processed.
// They have an ordering operator which sorts them by depth and then index.
// We use double precision for 'viz', for reasons described in the 'VIZ'
// section of the explanatory comments in the PxDeepUtils library.
struct Span
{
    Span () : in (0.0f), out (0.0f), viz (0.0), index (0) {}

    float  in;
    float  out;
    double viz;
    int    index;

    void clear ()
    {
        in    = 0.0f;
        out   = 0.0f;
        viz   = 0.0;
        index = 0;
    }

    bool operator< (const Span& i_other) const
    {
        if (in < i_other.in) { return true; }
        else if (in == i_other.in) { return index < i_other.index; }
        else { return false; }
    }
};

//-*****************************************************************************
// Because the RGB values here are unpremultiplied, we use double precision
// to avoid precision loss when going (RGB/A)*A.
struct SpanRgba : public Span
{
    SpanRgba () : Span ()
    {
        rgb[0] = 0.0;
        rgb[1] = 0.0;
        rgb[2] = 0.0;
    }

    double rgb[3];

    void clear ()
    {
        Span::clear ();
        rgb[0] = 0.0;
        rgb[1] = 0.0;
        rgb[2] = 0.0;
    }
};

//-*****************************************************************************
// As above, we use double precision for viz.
struct SpanOpac : public Span
{
    SpanOpac () : Span (), deepViz (0.0) {}

    double deepViz;

    void clear ()
    {
        Span::clear ();
        deepViz = 0.0;
    }
};

//-*****************************************************************************
// The box processing simply loops over the rows, compresses each pixel, then
// converts from dtex representation to deep exr representation, and finally
// writes the rows to the file.
template <typename RGBA_T, typename DERIVED, typename SPAN>
void
BaseDeepHelper<RGBA_T, DERIVED, SPAN>::processDeepBox (
    Imf::DeepScanLineOutputFile& o_file, const Imath::Box2i& i_box)
{
    int width = (i_box.max.x - i_box.min.x) + 1;

    DeepOutRow<RGBA_T> outRow (width, m_params.doDeepBack, m_params.doRGB);

    for (int y = i_box.max.y; y >= i_box.min.y; --y)
    {
        outRow.clear ();

        for (int x = i_box.min.x; x <= i_box.max.x; ++x)
        {
            if (m_params.sideways)
            {
                DtexGetPixel (
                    m_image,
                    m_fileWidth - 1 - y,
                    m_fileHeight - 1 - x,
                    m_rawPixel);
            }
            else
            {
                DtexGetPixel (m_image, x, m_fileHeight - 1 - y, m_rawPixel);
            }

            // Get the number of input points.
            int numPointsIn = DtexPixelGetNumPoints (m_rawPixel);
            if (numPointsIn < 0)
            {
                PXDU_THROW (
                    "Negative num points returned at dtex pixel: " << x << ", "
                                                                   << y);
            }

            // Compress the pixel.
            if (numPointsIn > 1 && m_params.compressionError > 0.0f)
            {
                DtexCompressPixel (
                    m_rawPixel, m_pixel, m_params.compressionError);
                DtexFinishPixel (m_pixel);
            }
            else
            {
                DtexCopyPixel (m_pixel, m_rawPixel);
                DtexFinishPixel (m_pixel);
            }

            // Get num points of compressed pixel.
            int numPts = DtexPixelGetNumPoints (m_pixel);

            // If no samples here, continue on.
            if (numPts < 1)
            {
                outRow.addHole (x - i_box.min.x);
                continue;
            }

            m_deepOutPixel.clear ();
            m_deepOutPixel.reserve (numPts * m_numDtexChans);

            // Process the deep pixels.
            DERIVED* derivedThis = static_cast<DERIVED*> (this);
            derivedThis->processDeepPixel (numPts);

            // Add the pixel to the row.
            outRow.addPixel (x - i_box.min.x, m_deepOutPixel);
        }

        // Create the frame buffer.
        // I'm not sure if this can be reused from row to row.
        Imf::DeepFrameBuffer frameBuffer;

        // Set the deep out row into the framebuffer.
        outRow.setFrameBuffer (frameBuffer);

        // Write row.
        o_file.setFrameBuffer (frameBuffer);
        o_file.writePixels (1);
    }
}

} // End namespace PxDeep

#endif