/******************************************************************************
 *
 * Project:  GDAL
 * Purpose:  "hillshade" step of "raster pipeline"
 * Author:   Even Rouault <even dot rouault at spatialys.com>
 *
 ******************************************************************************
 * Copyright (c) 2025, Even Rouault <even dot rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "gdalalg_raster_hillshade.h"

#include "gdal_priv.h"
#include "gdal_utils.h"

#include <cmath>

//! @cond Doxygen_Suppress

#ifndef _
#define _(x) (x)
#endif

/************************************************************************/
/*       GDALRasterHillshadeAlgorithm::GDALRasterHillshadeAlgorithm()   */
/************************************************************************/

GDALRasterHillshadeAlgorithm::GDALRasterHillshadeAlgorithm(bool standaloneStep)
    : GDALRasterPipelineStepAlgorithm(NAME, DESCRIPTION, HELP_URL,
                                      standaloneStep)
{
    SetOutputVRTCompatible(false);

    AddBandArg(&m_band).SetDefault(m_band);
    AddArg("zfactor", 'z',
           _("Vertical exaggeration used to pre-multiply the elevations"),
           &m_zfactor)
        .SetMinValueExcluded(0);
    AddArg("xscale", 0, _("Ratio of vertical units to horizontal X axis units"),
           &m_xscale)
        .SetMinValueExcluded(0);
    AddArg("yscale", 0, _("Ratio of vertical units to horizontal Y axis units"),
           &m_yscale)
        .SetMinValueExcluded(0);
    AddArg("azimuth", 0, _("Azimuth of the light, in degrees"), &m_azimuth)
        .SetDefault(m_azimuth);
    AddArg("altitude", 0, _("Altitude of the light, in degrees"), &m_altitude)
        .SetDefault(m_altitude)
        .SetMinValueIncluded(0)
        .SetMaxValueIncluded(90);
    AddArg("gradient-alg", 0, _("Algorithm used to compute terrain gradient"),
           &m_gradientAlg)
        .SetChoices("Horn", "ZevenbergenThorne")
        .SetDefault(m_gradientAlg);
    AddArg("variant", 0, _("Variant of the hillshading algorithm"), &m_variant)
        .SetChoices("regular", "combined", "multidirectional", "Igor")
        .SetDefault(m_variant);
    AddArg("no-edges", 0,
           _("Do not try to interpolate values at dataset edges or close to "
             "nodata values"),
           &m_noEdges);
}

/************************************************************************/
/*              GDALRasterHillshadeAlgorithm::RunStep()                 */
/************************************************************************/

bool GDALRasterHillshadeAlgorithm::RunStep(GDALProgressFunc, void *)
{
    CPLAssert(m_inputDataset.GetDatasetRef());
    CPLAssert(m_outputDataset.GetName().empty());
    CPLAssert(!m_outputDataset.GetDatasetRef());

    CPLStringList aosOptions;
    aosOptions.AddString("-of");
    aosOptions.AddString("stream");
    aosOptions.AddString("-b");
    aosOptions.AddString(CPLSPrintf("%d", m_band));
    aosOptions.AddString("-z");
    aosOptions.AddString(CPLSPrintf("%.17g", m_zfactor));
    if (!std::isnan(m_xscale))
    {
        aosOptions.AddString("-xscale");
        aosOptions.AddString(CPLSPrintf("%.17g", m_xscale));
    }
    if (!std::isnan(m_yscale))
    {
        aosOptions.AddString("-yscale");
        aosOptions.AddString(CPLSPrintf("%.17g", m_yscale));
    }
    if (m_variant == "multidirectional")
    {
        if (GetArg("azimuth")->IsExplicitlySet())
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "'azimuth' argument cannot be used with multidirectional "
                     "variant");
            return false;
        }
    }
    else
    {
        aosOptions.AddString("-az");
        aosOptions.AddString(CPLSPrintf("%.17g", m_azimuth));
    }
    if (m_variant == "Igor")
    {
        if (GetArg("altitude")->IsExplicitlySet())
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "'altitude' argument cannot be used with Igor variant");
            return false;
        }
    }
    else
    {
        aosOptions.AddString("-alt");
        aosOptions.AddString(CPLSPrintf("%.17g", m_altitude));
    }
    aosOptions.AddString("-alg");
    aosOptions.AddString(m_gradientAlg.c_str());

    if (m_variant == "combined")
        aosOptions.AddString("-combined");
    else if (m_variant == "multidirectional")
        aosOptions.AddString("-multidirectional");
    else if (m_variant == "Igor")
        aosOptions.AddString("-igor");

    if (!m_noEdges)
        aosOptions.AddString("-compute_edges");

    GDALDEMProcessingOptions *psOptions =
        GDALDEMProcessingOptionsNew(aosOptions.List(), nullptr);

    auto poOutDS =
        std::unique_ptr<GDALDataset>(GDALDataset::FromHandle(GDALDEMProcessing(
            "", GDALDataset::ToHandle(m_inputDataset.GetDatasetRef()),
            "hillshade", nullptr, psOptions, nullptr)));
    GDALDEMProcessingOptionsFree(psOptions);
    const bool bRet = poOutDS != nullptr;
    if (poOutDS)
    {
        m_outputDataset.Set(std::move(poOutDS));
    }

    return bRet;
}

//! @endcond