/******************************************************************************
 *
 * Project:  Ground-based SAR Applitcations Testbed File Format driver
 * Purpose:  Support in GDAL for Sandia National Laboratory's GFF format
 *           blame Tisham for putting me up to this
 * Author:   Philippe Vachon <philippe@cowpig.ca>
 *
 ******************************************************************************
 * Copyright (c) 2007, Philippe Vachon
 * Copyright (c) 2008-2012, Even Rouault <even dot rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_conv.h"
#include "cpl_port.h"
#include "cpl_string.h"
#include "cpl_vsi.h"
#include "gdal_frmts.h"
#include "gdal_pam.h"
#include "gdal_priv.h"

/*******************************************************************
 * Declaration of the GFFDataset class                             *
 *******************************************************************/

class GFFRasterBand;

class GFFDataset final : public GDALPamDataset
{
    friend class GFFRasterBand;
    VSILFILE *fp;
    GDALDataType eDataType;
    unsigned int nEndianness;
    /* Some relevant headers */
    unsigned short nVersionMajor;
    unsigned short nVersionMinor;
    unsigned int nLength;
    // char *pszCreator;
    //  TODO: Needs a better explanation.
    /* I am taking this at face value (are they insane?) */
    // float fBPP;
    unsigned int nBPP;

    /* Good information to know */
    unsigned int nFrameCnt;
    unsigned int nImageType;
    unsigned int nRowMajor;
    unsigned int nRgCnt;
    unsigned int nAzCnt;
    // long nScaleExponent;
    // long nScaleMantissa;
    // long nOffsetExponent;
    // long nOffsetMantissa;
  public:
    GFFDataset();
    ~GFFDataset();

    static GDALDataset *Open(GDALOpenInfo *);
    static int Identify(GDALOpenInfo *poOpenInfo);
};

GFFDataset::GFFDataset()
    : fp(nullptr), eDataType(GDT_Unknown), nEndianness(0), nVersionMajor(0),
      nVersionMinor(0), nLength(0), nBPP(0), nFrameCnt(0), nImageType(0),
      nRowMajor(0), nRgCnt(0), nAzCnt(0)
{
}

GFFDataset::~GFFDataset()
{
    if (fp != nullptr)
        VSIFCloseL(fp);
}

/*********************************************************************
 * Declaration and implementation of the GFFRasterBand Class         *
 *********************************************************************/

class GFFRasterBand final : public GDALPamRasterBand
{
    long nRasterBandMemory;
    int nSampleSize;

  public:
    GFFRasterBand(GFFDataset *, int, GDALDataType);
    CPLErr IReadBlock(int, int, void *) override;
};

static unsigned long GFFSampleSize(GDALDataType eDataType)
{
    // Determine the number of bytes per sample.
    unsigned long nBytes = 1;
    switch (eDataType)
    {
        case GDT_CInt16:
            nBytes = 4;
            break;
        case GDT_CInt32:
        case GDT_CFloat32:
            nBytes = 8;
            break;
        default:
            nBytes = 1;
    }

    return nBytes;
}

/************************************************************************/
/*                           GFFRasterBand()                            */
/************************************************************************/
GFFRasterBand::GFFRasterBand(GFFDataset *poDSIn, int nBandIn,
                             GDALDataType eDataTypeIn)
    : nRasterBandMemory(GFFSampleSize(eDataTypeIn) * poDSIn->GetRasterXSize()),
      nSampleSize(static_cast<int>(GFFSampleSize(eDataTypeIn)))
{
    poDS = poDSIn;
    nBand = nBandIn;

    eDataType = eDataTypeIn;

    nBlockXSize = poDS->GetRasterXSize();
    nBlockYSize = 1;
}

/************************************************************************/
/*                             IReadBlock()                             */
/************************************************************************/

CPLErr GFFRasterBand::IReadBlock(int /* nBlockXOff */, int nBlockYOff,
                                 void *pImage)
{
    GFFDataset *poGDS = (GFFDataset *)poDS;
    long nOffset = poGDS->nLength;

    VSIFSeekL(poGDS->fp,
              nOffset + (poGDS->GetRasterXSize() * nBlockYOff * (nSampleSize)),
              SEEK_SET);

    /* Ingest entire range line */
    if (VSIFReadL(pImage, nRasterBandMemory, 1, poGDS->fp) != 1)
        return CE_Failure;

#if defined(CPL_MSB)
    if (GDALDataTypeIsComplex(eDataType))
    {
        int nWordSize = GDALGetDataTypeSize(eDataType) / 16;
        GDALSwapWords(pImage, nWordSize, nBlockXSize, 2 * nWordSize);
        GDALSwapWords(((GByte *)pImage) + nWordSize, nWordSize, nBlockXSize,
                      2 * nWordSize);
    }
#endif

    return CE_None;
}

/********************************************************************
 * ================================================================ *
 * Implementation of the GFFDataset Class                           *
 * ================================================================ *
 ********************************************************************/

/************************************************************************/
/*                              Identify()                              */
/************************************************************************/
int GFFDataset::Identify(GDALOpenInfo *poOpenInfo)
{
    if (poOpenInfo->nHeaderBytes < 7)
        return 0;

    if (STARTS_WITH_CI((char *)poOpenInfo->pabyHeader, "GSATIMG"))
        return 1;

    return 0;
}

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

GDALDataset *GFFDataset::Open(GDALOpenInfo *poOpenInfo)
{
    /* Check that the dataset is indeed a GSAT File Format (GFF) file */
    if (!GFFDataset::Identify(poOpenInfo) || poOpenInfo->fpL == nullptr)
        return nullptr;

    /* -------------------------------------------------------------------- */
    /*      Confirm the requested access is supported.                      */
    /* -------------------------------------------------------------------- */
    if (poOpenInfo->eAccess == GA_Update)
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "The GFF driver does not support update access to existing"
                 " datasets.\n");
        return nullptr;
    }

    GFFDataset *poDS = new GFFDataset();

    poDS->fp = poOpenInfo->fpL;
    poOpenInfo->fpL = nullptr;

    /* Check the endianness of the file */
    VSIFSeekL(poDS->fp, 54, SEEK_SET);
    VSIFReadL(&(poDS->nEndianness), 2, 1, poDS->fp);

    VSIFSeekL(poDS->fp, 8, SEEK_SET);
    VSIFReadL(&poDS->nVersionMinor, 2, 1, poDS->fp);
    CPL_LSBPTR16(&poDS->nVersionMinor);
    VSIFReadL(&poDS->nVersionMajor, 2, 1, poDS->fp);
    CPL_LSBPTR16(&poDS->nVersionMajor);
    VSIFReadL(&poDS->nLength, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nLength);

    unsigned short nCreatorLength = 0;
    VSIFReadL(&nCreatorLength, 2, 1, poDS->fp);
    CPL_LSBPTR16(&nCreatorLength);
    /* Hack for now... I should properly load the date metadata, for
     * example
     */
    VSIFSeekL(poDS->fp, 56, SEEK_SET);

    /* By looking at the Matlab code, one should write something like the
     * following test */
    /* but the results don't seem to be the ones really expected */
    /*if ((poDS->nVersionMajor == 1 && poDS->nVersionMinor > 7) ||
    (poDS->nVersionMajor > 1))
    {
        float fBPP;
        VSIFRead(&fBPP,4,1,poDS->fp);
        poDS->nBPP = fBPP;
    }
    else*/
    {
        VSIFReadL(&poDS->nBPP, 4, 1, poDS->fp);
        CPL_LSBPTR32(&poDS->nBPP);
    }
    VSIFReadL(&poDS->nFrameCnt, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nFrameCnt);
    VSIFReadL(&poDS->nImageType, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nImageType);
    VSIFReadL(&poDS->nRowMajor, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nRowMajor);
    VSIFReadL(&poDS->nRgCnt, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nRgCnt);
    VSIFReadL(&poDS->nAzCnt, 4, 1, poDS->fp);
    CPL_LSBPTR32(&poDS->nAzCnt);

    /* We now have enough information to determine the number format */
    switch (poDS->nImageType)
    {
        case 0:
            poDS->eDataType = GDT_Byte;
            break;

        case 1:
            if (poDS->nBPP == 4)
                poDS->eDataType = GDT_CInt16;
            else
                poDS->eDataType = GDT_CInt32;
            break;

        case 2:
            poDS->eDataType = GDT_CFloat32;
            break;

        default:
            CPLError(CE_Failure, CPLE_AppDefined, "Unknown image type found!");
            delete poDS;
            return nullptr;
    }

    /* Set raster width/height
     * Note that the images that are complex are listed as having twice the
     * number of X-direction values than there are actual pixels. This is
     * because whoever came up with the format was crazy (actually, my
     * hunch is that they designed it very much for Matlab)
     * */
    if (poDS->nRowMajor)
    {
        poDS->nRasterXSize = poDS->nRgCnt / (poDS->nImageType == 0 ? 1 : 2);
        poDS->nRasterYSize = poDS->nAzCnt;
    }
    else
    {
        poDS->nRasterXSize = poDS->nAzCnt / (poDS->nImageType == 0 ? 1 : 2);
        poDS->nRasterYSize = poDS->nRgCnt;
    }

    if (poDS->nRasterXSize <= 0 || poDS->nRasterYSize <= 0)
    {
        CPLError(CE_Failure, CPLE_AppDefined,
                 "Invalid raster dimensions : %d x %d", poDS->nRasterXSize,
                 poDS->nRasterYSize);
        delete poDS;
        return nullptr;
    }

    poDS->SetBand(1, new GFFRasterBand(poDS, 1, poDS->eDataType));

    /* -------------------------------------------------------------------- */
    /*      Initialize any PAM information.                                 */
    /* -------------------------------------------------------------------- */
    poDS->SetDescription(poOpenInfo->pszFilename);
    poDS->TryLoadXML();

    /* -------------------------------------------------------------------- */
    /*      Support overviews.                                              */
    /* -------------------------------------------------------------------- */
    poDS->oOvManager.Initialize(poDS, poOpenInfo->pszFilename);

    return poDS;
}

/************************************************************************/
/*                          GDALRegister_GFF()                          */
/************************************************************************/

void GDALRegister_GFF()
{
    if (GDALGetDriverByName("GFF") != nullptr)
        return;

    GDALDriver *poDriver = new GDALDriver();

    poDriver->SetDescription("GFF");
    poDriver->SetMetadataItem(GDAL_DCAP_RASTER, "YES");
    poDriver->SetMetadataItem(
        GDAL_DMD_LONGNAME,
        "Ground-based SAR Applications Testbed File Format (.gff)");
    poDriver->SetMetadataItem(GDAL_DMD_HELPTOPIC, "drivers/raster/gff.html");
    poDriver->SetMetadataItem(GDAL_DMD_EXTENSION, "gff");
    poDriver->SetMetadataItem(GDAL_DCAP_VIRTUALIO, "YES");
    poDriver->pfnOpen = GFFDataset::Open;
    GetGDALDriverManager()->RegisterDriver(poDriver);
}
