/******************************************************************************
 *
 * Project:  Raster Matrix Format
 * Purpose:  Implementation of the ad-hoc compression algorithm used in
 *           GIS "Panorama"/"Integratsia".
 * Author:   Andrey Kiselev, dron@ak4719.spb.edu
 *
 ******************************************************************************
 * Copyright (c) 2009, Andrey Kiselev <dron@ak4719.spb.edu>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_conv.h"

#include "rmfdataset.h"

#include <limits>

/*
 * The encoded data stream is a series of records.
 *
 * Encoded record consist from the 1-byte record header followed by the
 * encoded data block. Header specifies the number of elements in the data
 * block and encoding type. Header format
 *
 * +---+---+---+---+---+---+---+---+
 * |   type    |       count       |
 * +---+---+---+---+---+---+---+---+
 *   7   6   5   4   3   2   1   0
 *
 * If count is zero then it means that there are more than 31 elements in this
 * record. Read the next byte in the stream and increase its value with 32 to
 * get the count. In this case maximum number of elements is 287.
 *
 * The "type" field specifies encoding type. It can be either difference
 * between the previous and the next data value (for the first element the
 * previous value is zero) or out-of-range codes.
 *
 * In case of "out of range" or "zero difference" values there are no more
 * elements in record after the header. Otherwise read as much encoded
 * elements as count specifies.
 */

typedef GInt32 DEMWorkT;
typedef GInt64 DEMDiffT;

// Encoding types
enum RmfTypes
{
    TYPE_OUT = 0x00,    // Value is out of range
    TYPE_ZERO = 0x20,   // Zero difference
    TYPE_INT4 = 0x40,   // Difference is 4-bit wide
    TYPE_INT8 = 0x60,   // Difference is 8-bit wide
    TYPE_INT12 = 0x80,  // Difference is 12-bit wide
    TYPE_INT16 = 0xA0,  // Difference is 16-bit wide
    TYPE_INT24 = 0xC0,  // Difference is 24-bit wide
    TYPE_INT32 = 0xE0   // Difference is 32-bit wide
};

// Encoding ranges
GInt32 RANGE_INT4 = 0x00000007L;   // 4-bit
GInt32 RANGE_INT8 = 0x0000007FL;   // 8-bit
GInt32 RANGE_INT12 = 0x000007FFL;  // 12-bit
GInt32 RANGE_INT16 = 0x00007FFFL;  // 16-bit
GInt32 RANGE_INT24 = 0x007FFFFFL;  // 24-bit

// Out of range codes
GInt32 OUT_INT4 = 0xFFFFFFF8;
GInt32 OUT_INT8 = 0xFFFFFF80;
GInt32 OUT_INT12 = 0xFFFFF800;
GInt32 OUT_INT16 = 0xFFFF8000;
GInt32 OUT_INT24 = 0xFF800000;
GInt32 OUT_INT32 = 0x80000000;

constexpr DEMDiffT DIFF_OUI_OF_RANGE = std::numeric_limits<DEMDiffT>::max();

// Inversion masks
GInt32 INV_INT4 = 0xFFFFFFF0L;
GInt32 INV_INT12 = 0xFFFFF000L;
GInt32 INV_INT24 = 0xFF000000L;

// Not sure which behavior we wish for int32 overflow, so just do the
// addition as uint32 to workaround -ftrapv
CPL_NOSANITIZE_UNSIGNED_INT_OVERFLOW
static GInt32 AddInt32(GInt32 &nTarget, GInt32 nVal)
{
    GUInt32 nTargetU = static_cast<GUInt32>(nTarget);
    GUInt32 nValU = static_cast<GUInt32>(nVal);
    nTargetU += nValU;
    memcpy(&nTarget, &nTargetU, 4);
    return nTarget;
}

/************************************************************************/
/*                           DEMDecompress()                            */
/************************************************************************/

size_t RMFDataset::DEMDecompress(const GByte *pabyIn, GUInt32 nSizeIn,
                                 GByte *pabyOut, GUInt32 nSizeOut, GUInt32,
                                 GUInt32)
{
    if (pabyIn == nullptr || pabyOut == nullptr || nSizeOut < nSizeIn ||
        nSizeIn < 2)
        return 0;

    GInt32 iPrev = 0;  // The last data value decoded.

    const signed char *pabyTempIn =
        reinterpret_cast<const signed char *>(pabyIn);
    GInt32 *paiOut = reinterpret_cast<GInt32 *>(pabyOut);
    nSizeOut /= sizeof(GInt32);

    while (nSizeIn > 0)
    {
        // Read number of codes in the record and encoding type.
        GUInt32 nCount = *pabyTempIn & 0x1F;
        const GUInt32 nType = *pabyTempIn++ & 0xE0;  // The encoding type.
        nSizeIn--;
        if (nCount == 0)
        {
            if (nSizeIn == 0)
                break;
            nCount = 32 + *((GByte *)pabyTempIn++);
            nSizeIn--;
        }

        switch (nType)
        {
            case TYPE_ZERO:
                if (nSizeOut < nCount)
                    break;
                nSizeOut -= nCount;
                while (nCount > 0)
                {
                    nCount--;
                    *paiOut++ = iPrev;
                }
                break;

            case TYPE_OUT:
                if (nSizeOut < nCount)
                    break;
                nSizeOut -= nCount;
                while (nCount > 0)
                {
                    nCount--;
                    *paiOut++ = OUT_INT32;
                }
                break;

            case TYPE_INT4:
                if (nSizeIn < (nCount + 1) / 2)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= nCount / 2;
                nSizeOut -= nCount;
                while (nCount > 0)
                {
                    nCount--;
                    GInt32 nCode;
                    nCode = (*pabyTempIn) & 0x0F;
                    if (nCode > RANGE_INT4)
                        nCode |= INV_INT4;
                    *paiOut++ = (nCode == OUT_INT4) ? OUT_INT32
                                                    : AddInt32(iPrev, nCode);

                    if (nCount == 0)
                    {
                        if (nSizeIn)
                        {
                            pabyTempIn++;
                            nSizeIn--;
                        }
                        break;
                    }
                    nCount--;

                    nCode = ((*pabyTempIn++) >> 4) & 0x0F;
                    if (nCode > RANGE_INT4)
                        nCode |= INV_INT4;
                    *paiOut++ = (nCode == OUT_INT4) ? OUT_INT32
                                                    : AddInt32(iPrev, nCode);
                }
                break;

            case TYPE_INT8:
                if (nSizeIn < nCount)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= nCount;
                nSizeOut -= nCount;
                while (nCount > 0)
                {
                    nCount--;
                    GInt32 nCode;
                    *paiOut++ = ((nCode = *pabyTempIn++) == OUT_INT8)
                                    ? OUT_INT32
                                    : AddInt32(iPrev, nCode);
                }
                break;

            case TYPE_INT12:
                if (nSizeIn < (3 * nCount + 1) / 2)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= 3 * nCount / 2;
                nSizeOut -= nCount;

                while (nCount > 0)
                {
                    nCount--;
                    GInt32 nCode = CPL_LSBSINT16PTR(pabyTempIn) & 0x0FFF;
                    pabyTempIn += 1;
                    if (nCode > RANGE_INT12)
                        nCode |= INV_INT12;
                    *paiOut++ = (nCode == OUT_INT12) ? OUT_INT32
                                                     : AddInt32(iPrev, nCode);

                    if (nCount == 0)
                    {
                        if (nSizeIn)
                        {
                            pabyTempIn++;
                            nSizeIn--;
                        }
                        break;
                    }
                    nCount--;

                    nCode = (CPL_LSBSINT16PTR(pabyTempIn) >> 4) & 0x0FFF;
                    pabyTempIn += 2;
                    if (nCode > RANGE_INT12)
                        nCode |= INV_INT12;
                    *paiOut++ = (nCode == OUT_INT12) ? OUT_INT32
                                                     : AddInt32(iPrev, nCode);
                }
                break;

            case TYPE_INT16:
                if (nSizeIn < 2 * nCount)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= 2 * nCount;
                nSizeOut -= nCount;

                while (nCount > 0)
                {
                    nCount--;
                    const GInt32 nCode = CPL_LSBSINT16PTR(pabyTempIn);
                    pabyTempIn += 2;
                    *paiOut++ = (nCode == OUT_INT16) ? OUT_INT32
                                                     : AddInt32(iPrev, nCode);
                }
                break;

            case TYPE_INT24:
                if (nSizeIn < 3 * nCount)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= 3 * nCount;
                nSizeOut -= nCount;

                while (nCount > 0)
                {
                    nCount--;
                    GInt32 nCode = (*(GByte *)pabyTempIn) |
                                   ((*(GByte *)(pabyTempIn + 1)) << 8) |
                                   ((*(GByte *)(pabyTempIn + 2)) << 16);
                    pabyTempIn += 3;
                    if (nCode > RANGE_INT24)
                        nCode |= INV_INT24;
                    *paiOut++ = (nCode == OUT_INT24) ? OUT_INT32
                                                     : AddInt32(iPrev, nCode);
                }
                break;

            case TYPE_INT32:
                if (nSizeIn < 4 * nCount)
                    break;
                if (nSizeOut < nCount)
                    break;
                nSizeIn -= 4 * nCount;
                nSizeOut -= nCount;

                while (nCount > 0)
                {
                    nCount--;
                    GInt32 nCode = CPL_LSBSINT32PTR(pabyTempIn);
                    pabyTempIn += 4;
                    *paiOut++ = (nCode == OUT_INT32) ? OUT_INT32
                                                     : AddInt32(iPrev, nCode);
                }
                break;
        }
    }

    return (GByte *)paiOut - pabyOut;
}

/************************************************************************/
/*                            DEMWriteCode()                            */
/************************************************************************/

static CPLErr DEMWriteRecord(const DEMDiffT *paiRecord, RmfTypes eRecordType,
                             GUInt32 nRecordSize, GInt32 nSizeOut,
                             GByte *&pabyCurrent)
{
    const GUInt32 nMaxCountInHeader = 31;
    GInt32 iCode;
    GInt32 iPrevCode;

    if (nRecordSize <= nMaxCountInHeader)
    {
        nSizeOut -= 1;
        if (nSizeOut <= 0)
        {
            return CE_Failure;
        }

        *pabyCurrent++ = static_cast<GByte>(eRecordType | nRecordSize);
    }
    else
    {
        nSizeOut -= 2;
        if (nSizeOut <= 0)
        {
            return CE_Failure;
        }

        *pabyCurrent++ = static_cast<GByte>(eRecordType);
        *pabyCurrent++ = static_cast<GByte>(nRecordSize - 32);
    }

    switch (eRecordType)
    {
        case TYPE_INT4:
            nSizeOut -= ((nRecordSize + 1) / 2);
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT4;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                *pabyCurrent = static_cast<GByte>(iCode & 0x0F);

                ++n;
                if (n == nRecordSize)
                {
                    pabyCurrent++;
                    break;
                }

                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT4;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                *pabyCurrent++ |= static_cast<GByte>((iCode & 0x0F) << 4);
            }
            break;

        case TYPE_INT8:
            nSizeOut -= nRecordSize;
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    *pabyCurrent++ = static_cast<GByte>(OUT_INT8);
                }
                else
                {
                    *pabyCurrent++ = static_cast<GByte>(paiRecord[n]);
                }
            }
            break;

        case TYPE_INT12:
            nSizeOut -= ((nRecordSize * 3 + 1) / 2);
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT12;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }

                iPrevCode = iCode;
                *pabyCurrent++ = static_cast<GByte>(iCode & 0x00FF);

                ++n;
                if (n == nRecordSize)
                {
                    *pabyCurrent++ =
                        static_cast<GByte>((iPrevCode & 0x0F00) >> 8);
                    break;
                }

                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT12;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                iCode = (((iPrevCode & 0x0F00) >> 8) | ((iCode & 0x0FFF) << 4));

                CPL_LSBPTR32(&iCode);
                memcpy(pabyCurrent, &iCode, 2);
                pabyCurrent += 2;
            }
            break;

        case TYPE_INT16:
            nSizeOut -= (nRecordSize * 2);
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT16;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                CPL_LSBPTR32(&iCode);
                memcpy(pabyCurrent, &iCode, 2);
                pabyCurrent += 2;
            }
            break;

        case TYPE_INT24:
            nSizeOut -= (nRecordSize * 3);
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT24;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                CPL_LSBPTR32(&iCode);
                memcpy(pabyCurrent, &iCode, 3);
                pabyCurrent += 3;
            }
            break;

        case TYPE_INT32:
            nSizeOut -= (nRecordSize * 4);
            if (nSizeOut <= 0)
            {
                return CE_Failure;
            }

            for (GUInt32 n = 0; n != nRecordSize; ++n)
            {
                if (paiRecord[n] == DIFF_OUI_OF_RANGE)
                {
                    iCode = OUT_INT32;
                }
                else
                {
                    iCode = static_cast<GInt32>(paiRecord[n]);
                }
                CPL_LSBPTR32(&iCode);
                memcpy(pabyCurrent, &iCode, 4);
                pabyCurrent += 4;
            }
            break;

        case TYPE_ZERO:
        case TYPE_OUT:
            break;

        default:
            return CE_Failure;
    }

    return CE_None;
}

/************************************************************************/
/*                             DEMDeltaType()                           */
/************************************************************************/

static RmfTypes DEMDeltaType(DEMDiffT delta)
{
    if (delta <= RANGE_INT12)
    {
        if (delta <= RANGE_INT4)
        {
            if (delta == 0)
            {
                return TYPE_ZERO;
            }
            else
            {
                return TYPE_INT4;
            }
        }
        else
        {
            if (delta <= RANGE_INT8)
            {
                return TYPE_INT8;
            }
            else
            {
                return TYPE_INT12;
            }
        }
    }
    else
    {
        if (delta <= RANGE_INT24)
        {
            if (delta <= RANGE_INT16)
            {
                return TYPE_INT16;
            }
            else
            {
                return TYPE_INT24;
            }
        }
        else
        {
            return TYPE_INT32;
        }
    }
}

/************************************************************************/
/*                             DEMCompress()                            */
/************************************************************************/

size_t RMFDataset::DEMCompress(const GByte *pabyIn, GUInt32 nSizeIn,
                               GByte *pabyOut, GUInt32 nSizeOut, GUInt32,
                               GUInt32, const RMFDataset *poDS)
{
    if (pabyIn == nullptr || pabyOut == nullptr || nSizeIn < sizeof(DEMWorkT))
        return 0;

    const GUInt32 anDeltaTypeSize[8] = {0, 0, 4, 8, 12, 16, 24, 32};
    const GUInt32 nMaxRecordSize = 255 + 32;

    DEMWorkT iMin(std::numeric_limits<DEMWorkT>::min() + 1);
    if (poDS != nullptr &&
        poDS->sHeader.adfElevMinMax[0] < poDS->sHeader.adfElevMinMax[1])
    {
        iMin = static_cast<DEMWorkT>(poDS->sHeader.adfElevMinMax[0]);
    }
    GUInt32 nLessCount = 0;
    GUInt32 nRecordSize = 0;
    RmfTypes eRecordType = TYPE_OUT;
    DEMDiffT aiRecord[nMaxRecordSize] = {0};
    DEMWorkT aiPrev[nMaxRecordSize] = {0};

    GByte *pabyCurrent = pabyOut;
    DEMWorkT iPrev = 0;

    nSizeIn = nSizeIn / sizeof(DEMWorkT);

    const DEMWorkT *paiIn = reinterpret_cast<const DEMWorkT *>(pabyIn);
    const DEMWorkT *paiInEnd = paiIn + nSizeIn;

    while (true)
    {
        GUInt32 nRecordElementSize = 0;

        if (paiIn >= paiInEnd)
        {
            if (nRecordSize == 0)
            {
                return pabyCurrent - pabyOut;
            }

            if (CE_None != DEMWriteRecord(aiRecord, eRecordType, nRecordSize,
                                          nSizeOut, pabyCurrent))
            {
                return 0;
            }
            nRecordSize = 0;
            continue;
        }

        DEMWorkT iCurr = *(paiIn++);
        RmfTypes eCurrType;

        if (iCurr < iMin)
        {
            eCurrType = TYPE_OUT;
            aiRecord[nRecordSize] = DIFF_OUI_OF_RANGE;
            aiPrev[nRecordSize] = iPrev;
        }
        else
        {
            DEMDiffT delta =
                static_cast<DEMDiffT>(iCurr) - static_cast<DEMDiffT>(iPrev);

            aiRecord[nRecordSize] = delta;
            aiPrev[nRecordSize] = iCurr;

            if (delta < 0)
                delta = -delta;

            eCurrType = DEMDeltaType(delta);
            iPrev = iCurr;
        }
        nRecordSize++;

        if (nRecordSize == 1)
        {
            eRecordType = eCurrType;
            // nRecordElementSize = anDeltaTypeSize[eCurrType >> 5];
            continue;
        }

        if (nRecordSize == nMaxRecordSize)
        {
            nLessCount = 0;
            if (CE_None != DEMWriteRecord(aiRecord, eRecordType, nRecordSize,
                                          nSizeOut, pabyCurrent))
            {
                return 0;
            }
            iPrev = aiPrev[nRecordSize - 1];
            nRecordSize = 0;
            continue;
        }

        if (eCurrType == eRecordType)
        {
            nLessCount = 0;
            continue;
        }

        if ((eCurrType > eRecordType) || (eCurrType | eRecordType) == TYPE_ZERO)
        {
            --paiIn;
            if (CE_None != DEMWriteRecord(aiRecord, eRecordType,
                                          nRecordSize - 1, nSizeOut,
                                          pabyCurrent))
            {
                return 0;
            }
            iPrev = aiPrev[nRecordSize - 2];
            nRecordSize = 0;
            nLessCount = 0;
            continue;
        }

        nLessCount++;

        GUInt32 nDeltaSize(anDeltaTypeSize[eCurrType >> 5]);
        if (nRecordElementSize < nDeltaSize ||
            (nRecordElementSize - nDeltaSize) * nLessCount < 16)
        {
            continue;
        }

        paiIn -= nLessCount;
        if (CE_None != DEMWriteRecord(aiRecord, eRecordType,
                                      nRecordSize - nLessCount, nSizeOut,
                                      pabyCurrent))
        {
            return 0;
        }
        iPrev = aiPrev[nRecordSize - nLessCount - 1];
        nRecordSize = 0;
        nLessCount = 0;
    }

    return 0;
}
