/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */


/* **************************************
*  Compiler Warnings
****************************************/
#ifdef _MSC_VER
#  pragma warning(disable : 4127)    /* disable: C4127: conditional expression is constant */
#endif


/*-*************************************
*  Includes
***************************************/
#include "platform.h"       /* Large Files support */
#include "util.h"           /* UTIL_getFileSize, UTIL_getTotalFileSize */
#include <stdlib.h>         /* malloc, free */
#include <string.h>         /* memset */
#include <stdio.h>          /* fprintf, fopen, ftello64 */
#include <time.h>           /* clock_t, clock, CLOCKS_PER_SEC */
#include <errno.h>          /* errno */

#include "mem.h"            /* read */
#include "error_private.h"
#include "dibio.h"


/*-*************************************
*  Constants
***************************************/
#define KB *(1 <<10)
#define MB *(1 <<20)
#define GB *(1U<<30)

#define SAMPLESIZE_MAX (128 KB)
#define MEMMULT 11    /* rough estimation : memory cost to analyze 1 byte of sample */
#define COVER_MEMMULT 9    /* rough estimation : memory cost to analyze 1 byte of sample */
static const size_t g_maxMemory = (sizeof(size_t) == 4) ? (2 GB - 64 MB) : ((size_t)(512 MB) << sizeof(size_t));

#define NOISELENGTH 32


/*-*************************************
*  Console display
***************************************/
#define DISPLAY(...)         fprintf(stderr, __VA_ARGS__)
#define DISPLAYLEVEL(l, ...) if (displayLevel>=l) { DISPLAY(__VA_ARGS__); }

#define DISPLAYUPDATE(l, ...) if (displayLevel>=l) { \
            if ((DIB_clockSpan(g_time) > refreshRate) || (displayLevel>=4)) \
            { g_time = clock(); DISPLAY(__VA_ARGS__); \
            if (displayLevel>=4) fflush(stderr); } }
static const clock_t refreshRate = CLOCKS_PER_SEC * 2 / 10;
static clock_t g_time = 0;

static clock_t DIB_clockSpan(clock_t nPrevious) { return clock() - nPrevious; }


/*-*************************************
*  Exceptions
***************************************/
#ifndef DEBUG
#  define DEBUG 0
#endif
#define DEBUGOUTPUT(...) if (DEBUG) DISPLAY(__VA_ARGS__);
#define EXM_THROW(error, ...)                                             \
{                                                                         \
    DEBUGOUTPUT("Error defined at %s, line %i : \n", __FILE__, __LINE__); \
    DISPLAY("Error %i : ", error);                                        \
    DISPLAY(__VA_ARGS__);                                                 \
    DISPLAY("\n");                                                        \
    exit(error);                                                          \
}


/* ********************************************************
*  Helper functions
**********************************************************/
unsigned DiB_isError(size_t errorCode) { return ERR_isError(errorCode); }

const char* DiB_getErrorName(size_t errorCode) { return ERR_getErrorName(errorCode); }

#undef MIN
#define MIN(a,b)    ((a) < (b) ? (a) : (b))


/* ********************************************************
*  File related operations
**********************************************************/
/** DiB_loadFiles() :
 *  load samples from files listed in fileNamesTable into buffer.
 *  works even if buffer is too small to load all samples.
 *  Also provides the size of each sample into sampleSizes table
 *  which must be sized correctly, using DiB_fileStats().
 * @return : nb of samples effectively loaded into `buffer`
 * *bufferSizePtr is modified, it provides the amount data loaded within buffer.
 *  sampleSizes is filled with the size of each sample.
 */
static unsigned DiB_loadFiles(void* buffer, size_t* bufferSizePtr,
                              size_t* sampleSizes, unsigned sstSize,
                              const char** fileNamesTable, unsigned nbFiles, size_t targetChunkSize,
                              unsigned displayLevel)
{
    char* const buff = (char*)buffer;
    size_t pos = 0;
    unsigned nbLoadedChunks = 0, fileIndex;

    for (fileIndex=0; fileIndex<nbFiles; fileIndex++) {
        const char* const fileName = fileNamesTable[fileIndex];
        unsigned long long const fs64 = UTIL_getFileSize(fileName);
        unsigned long long remainingToLoad = fs64;
        U32 const nbChunks = targetChunkSize ? (U32)((fs64 + (targetChunkSize-1)) / targetChunkSize) : 1;
        U64 const chunkSize = targetChunkSize ? MIN(targetChunkSize, fs64) : fs64;
        size_t const maxChunkSize = (size_t)MIN(chunkSize, SAMPLESIZE_MAX);
        U32 cnb;
        FILE* const f = fopen(fileName, "rb");
        if (f==NULL) EXM_THROW(10, "zstd: dictBuilder: %s %s ", fileName, strerror(errno));
        DISPLAYUPDATE(2, "Loading %s...       \r", fileName);
        for (cnb=0; cnb<nbChunks; cnb++) {
            size_t const toLoad = (size_t)MIN(maxChunkSize, remainingToLoad);
            if (toLoad > *bufferSizePtr-pos) break;
            {   size_t const readSize = fread(buff+pos, 1, toLoad, f);
                if (readSize != toLoad) EXM_THROW(11, "Pb reading %s", fileName);
                pos += readSize;
                sampleSizes[nbLoadedChunks++] = toLoad;
                remainingToLoad -= targetChunkSize;
                if (nbLoadedChunks == sstSize) { /* no more space left in sampleSizes table */
                    fileIndex = nbFiles;  /* stop there */
                    break;
                }
                if (toLoad < targetChunkSize) {
                    fseek(f, (long)(targetChunkSize - toLoad), SEEK_CUR);
        }   }   }
        fclose(f);
    }
    DISPLAYLEVEL(2, "\r%79s\r", "");
    *bufferSizePtr = pos;
    DISPLAYLEVEL(4, "loaded : %u KB \n", (U32)(pos >> 10))
    return nbLoadedChunks;
}

#define DiB_rotl32(x,r) ((x << r) | (x >> (32 - r)))
static U32 DiB_rand(U32* src)
{
    static const U32 prime1 = 2654435761U;
    static const U32 prime2 = 2246822519U;
    U32 rand32 = *src;
    rand32 *= prime1;
    rand32 ^= prime2;
    rand32  = DiB_rotl32(rand32, 13);
    *src = rand32;
    return rand32 >> 5;
}

/* DiB_shuffle() :
 * shuffle a table of file names in a semi-random way
 * It improves dictionary quality by reducing "locality" impact, so if sample set is very large,
 * it will load random elements from it, instead of just the first ones. */
static void DiB_shuffle(const char** fileNamesTable, unsigned nbFiles) {
    U32 seed = 0xFD2FB528;
    unsigned i;
    for (i = nbFiles - 1; i > 0; --i) {
        unsigned const j = DiB_rand(&seed) % (i + 1);
        const char* const tmp = fileNamesTable[j];
        fileNamesTable[j] = fileNamesTable[i];
        fileNamesTable[i] = tmp;
    }
}


/*-********************************************************
*  Dictionary training functions
**********************************************************/
static size_t DiB_findMaxMem(unsigned long long requiredMem)
{
    size_t const step = 8 MB;
    void* testmem = NULL;

    requiredMem = (((requiredMem >> 23) + 1) << 23);
    requiredMem += step;
    if (requiredMem > g_maxMemory) requiredMem = g_maxMemory;

    while (!testmem) {
        testmem = malloc((size_t)requiredMem);
        requiredMem -= step;
    }

    free(testmem);
    return (size_t)requiredMem;
}


static void DiB_fillNoise(void* buffer, size_t length)
{
    unsigned const prime1 = 2654435761U;
    unsigned const prime2 = 2246822519U;
    unsigned acc = prime1;
    size_t p=0;;

    for (p=0; p<length; p++) {
        acc *= prime2;
        ((unsigned char*)buffer)[p] = (unsigned char)(acc >> 21);
    }
}


static void DiB_saveDict(const char* dictFileName,
                         const void* buff, size_t buffSize)
{
    FILE* const f = fopen(dictFileName, "wb");
    if (f==NULL) EXM_THROW(3, "cannot open %s ", dictFileName);

    { size_t const n = fwrite(buff, 1, buffSize, f);
      if (n!=buffSize) EXM_THROW(4, "%s : write error", dictFileName) }

    { size_t const n = (size_t)fclose(f);
      if (n!=0) EXM_THROW(5, "%s : flush error", dictFileName) }
}


typedef struct {
    U64 totalSizeToLoad;
    unsigned oneSampleTooLarge;
    unsigned nbSamples;
} fileStats;

/*! DiB_fileStats() :
 *  Given a list of files, and a chunkSize (0 == no chunk, whole files)
 *  provides the amount of data to be loaded and the resulting nb of samples.
 *  This is useful primarily for allocation purpose => sample buffer, and sample sizes table.
 */
static fileStats DiB_fileStats(const char** fileNamesTable, unsigned nbFiles, size_t chunkSize, unsigned displayLevel)
{
    fileStats fs;
    unsigned n;
    memset(&fs, 0, sizeof(fs));
    for (n=0; n<nbFiles; n++) {
        U64 const fileSize = UTIL_getFileSize(fileNamesTable[n]);
        U32 const nbSamples = (U32)(chunkSize ? (fileSize + (chunkSize-1)) / chunkSize : 1);
        U64 const chunkToLoad = chunkSize ? MIN(chunkSize, fileSize) : fileSize;
        size_t const cappedChunkSize = (size_t)MIN(chunkToLoad, SAMPLESIZE_MAX);
        fs.totalSizeToLoad += cappedChunkSize * nbSamples;
        fs.oneSampleTooLarge |= (chunkSize > 2*SAMPLESIZE_MAX);
        fs.nbSamples += nbSamples;
    }
    DISPLAYLEVEL(4, "Preparing to load : %u KB \n", (U32)(fs.totalSizeToLoad >> 10));
    return fs;
}


/*! ZDICT_trainFromBuffer_unsafe_legacy() :
    Strictly Internal use only !!
    Same as ZDICT_trainFromBuffer_legacy(), but does not control `samplesBuffer`.
    `samplesBuffer` must be followed by noisy guard band to avoid out-of-buffer reads.
    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
              or an error code.
*/
size_t ZDICT_trainFromBuffer_unsafe_legacy(void* dictBuffer, size_t dictBufferCapacity,
                                           const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
                                           ZDICT_legacy_params_t parameters);


int DiB_trainFromFiles(const char* dictFileName, unsigned maxDictSize,
                       const char** fileNamesTable, unsigned nbFiles, size_t chunkSize,
                       ZDICT_legacy_params_t *params, ZDICT_cover_params_t *coverParams,
                       int optimizeCover)
{
    unsigned const displayLevel = params ? params->zParams.notificationLevel :
                        coverParams ? coverParams->zParams.notificationLevel :
                        0;   /* should never happen */
    void* const dictBuffer = malloc(maxDictSize);
    fileStats const fs = DiB_fileStats(fileNamesTable, nbFiles, chunkSize, displayLevel);
    size_t* const sampleSizes = (size_t*)malloc(fs.nbSamples * sizeof(size_t));
    size_t const memMult = params ? MEMMULT : COVER_MEMMULT;
    size_t const maxMem =  DiB_findMaxMem(fs.totalSizeToLoad * memMult) / memMult;
    size_t loadedSize = (size_t) MIN ((unsigned long long)maxMem, fs.totalSizeToLoad);
    void* const srcBuffer = malloc(loadedSize+NOISELENGTH);
    int result = 0;

    /* Checks */
    if ((!sampleSizes) || (!srcBuffer) || (!dictBuffer))
        EXM_THROW(12, "not enough memory for DiB_trainFiles");   /* should not happen */
    if (fs.oneSampleTooLarge) {
        DISPLAYLEVEL(2, "!  Warning : some sample(s) are very large \n");
        DISPLAYLEVEL(2, "!  Note that dictionary is only useful for small samples. \n");
        DISPLAYLEVEL(2, "!  As a consequence, only the first %u bytes of each sample are loaded \n", SAMPLESIZE_MAX);
    }
    if (fs.nbSamples < 5) {
        DISPLAYLEVEL(2, "!  Warning : nb of samples too low for proper processing ! \n");
        DISPLAYLEVEL(2, "!  Please provide _one file per sample_. \n");
        DISPLAYLEVEL(2, "!  Alternatively, split files into fixed-size blocks representative of samples, with -B# \n");
        EXM_THROW(14, "nb of samples too low");   /* we now clearly forbid this case */
    }
    if (fs.totalSizeToLoad < (unsigned long long)(8 * maxDictSize)) {
        DISPLAYLEVEL(2, "!  Warning : data size of samples too small for target dictionary size \n");
        DISPLAYLEVEL(2, "!  Samples should be about 100x larger than target dictionary size \n");
    }

    /* init */
    if (loadedSize < fs.totalSizeToLoad)
        DISPLAYLEVEL(1, "Not enough memory; training on %u MB only...\n", (unsigned)(loadedSize >> 20));

    /* Load input buffer */
    DISPLAYLEVEL(3, "Shuffling input files\n");
    DiB_shuffle(fileNamesTable, nbFiles);
    nbFiles = DiB_loadFiles(srcBuffer, &loadedSize, sampleSizes, fs.nbSamples, fileNamesTable, nbFiles, chunkSize, displayLevel);

    {   size_t dictSize;
        if (params) {
            DiB_fillNoise((char*)srcBuffer + loadedSize, NOISELENGTH);   /* guard band, for end of buffer condition */
            dictSize = ZDICT_trainFromBuffer_unsafe_legacy(dictBuffer, maxDictSize,
                                                           srcBuffer, sampleSizes, fs.nbSamples,
                                                           *params);
        } else if (optimizeCover) {
            dictSize = ZDICT_optimizeTrainFromBuffer_cover(dictBuffer, maxDictSize,
                                                           srcBuffer, sampleSizes, fs.nbSamples,
                                                           coverParams);
            if (!ZDICT_isError(dictSize)) {
                DISPLAYLEVEL(2, "k=%u\nd=%u\nsteps=%u\n", coverParams->k, coverParams->d, coverParams->steps);
            }
        } else {
            dictSize = ZDICT_trainFromBuffer_cover(dictBuffer, maxDictSize, srcBuffer,
                                                   sampleSizes, fs.nbSamples, *coverParams);
        }
        if (ZDICT_isError(dictSize)) {
            DISPLAYLEVEL(1, "dictionary training failed : %s \n", ZDICT_getErrorName(dictSize));   /* should not happen */
            result = 1;
            goto _cleanup;
        }
        /* save dict */
        DISPLAYLEVEL(2, "Save dictionary of size %u into file %s \n", (U32)dictSize, dictFileName);
        DiB_saveDict(dictFileName, dictBuffer, dictSize);
    }

    /* clean up */
_cleanup:
    free(srcBuffer);
    free(sampleSizes);
    free(dictBuffer);
    return result;
}