/*
  Dictionary decompression
  Educational program using zstd library
  Copyright (C) Yann Collet 2016

  GPL v2 License

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along
  with this program; if not, write to the Free Software Foundation, Inc.,
  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

  You can contact the author at :
  - zstd homepage : http://www.zstd.net/
*/

#include <stdlib.h>    // malloc, exit
#include <stdio.h>     // printf
#include <string.h>    // strerror
#include <errno.h>     // errno
#include <sys/stat.h>  // stat
#include <zstd.h>      // presumes zstd library is installed


static off_t fsize_X(const char *filename)
{
    struct stat st;
    if (stat(filename, &st) == 0) return st.st_size;
    /* error */
    perror(filename);
    exit(1);
}

static FILE* fopen_X(const char *filename, const char *instruction)
{
    FILE* const inFile = fopen(filename, instruction);
    if (inFile) return inFile;
    /* error */
    perror(filename);
    exit(2);
}

static void* malloc_X(size_t size)
{
    void* const buff = malloc(size);
    if (buff) return buff;
    /* error */
    perror(NULL);
    exit(3);
}

static void* loadFile_X(const char* fileName, size_t* size)
{
    off_t const buffSize = fsize_X(fileName);
    FILE* const inFile = fopen_X(fileName, "rb");
    void* const buffer = malloc_X(buffSize);
    size_t const readSize = fread(buffer, 1, buffSize, inFile);
    if (readSize != (size_t)buffSize) {
        fprintf(stderr, "fread: %s : %s \n", fileName, strerror(errno));
        exit(4);
    }
    fclose(inFile);
    *size = buffSize;
    return buffer;
}

static void saveFile_X(const char* fileName, const void* buff, size_t buffSize)
{
    FILE* const oFile = fopen_X(fileName, "wb");
    size_t const wSize = fwrite(buff, 1, buffSize, oFile);
    if (wSize != (size_t)buffSize) {
        fprintf(stderr, "fwrite: %s : %s \n", fileName, strerror(errno));
        exit(5);
    }
    if (fclose(oFile)) {
        perror(fileName);
        exit(6);
    }
}

/* createDict() :
   `dictFileName` is supposed to have been created using `zstd --train` */
static const ZSTD_CDict* createDict(const char* dictFileName)
{
    size_t dictSize;
    printf("loading dictionary %s \n", dictFileName);
    void* const dictBuffer = loadFile_X(dictFileName, &dictSize);
    const ZSTD_CDict* const ddict = ZSTD_createCDict(dictBuffer, dictSize, 3);
    free(dictBuffer);
    return ddict;
}


static void compress(const char* fname, const char* oname, const ZSTD_CDict* cdict)
{
    size_t fSize;
    void* const fBuff = loadFile_X(fname, &fSize);
    size_t const cBuffSize = ZSTD_compressBound(fSize);
    void* const cBuff = malloc_X(cBuffSize);

    ZSTD_CCtx* const cctx = ZSTD_createCCtx();
    size_t const cSize = ZSTD_compress_usingCDict(cctx, cBuff, cBuffSize, fBuff, fSize, cdict);
    if (ZSTD_isError(cSize)) {
        fprintf(stderr, "error compressing %s : %s \n", fname, ZSTD_getErrorName(cSize));
        exit(7);
    }

    saveFile_X(oname, cBuff, cSize);

    /* success */
    printf("%25s : %6u -> %7u - %s \n", fname, (unsigned)fSize, (unsigned)cSize, oname);

    ZSTD_freeCCtx(cctx);
    free(fBuff);
    free(cBuff);
}


static char* createOutFilename(const char* filename)
{
    size_t const inL = strlen(filename);
    size_t const outL = inL + 5;
    void* outSpace = malloc_X(outL);
    memset(outSpace, 0, outL);
    strcat(outSpace, filename);
    strcat(outSpace, ".zst");
    return (char*)outSpace;
}

int main(int argc, const char** argv)
{
    const char* const exeName = argv[0];

    if (argc<3) {
        fprintf(stderr, "wrong arguments\n");
        fprintf(stderr, "usage:\n");
        fprintf(stderr, "%s [FILES] dictionary\n", exeName);
        return 1;
    }

    /* load dictionary only once */
    const char* const dictName = argv[argc-1];
    const ZSTD_CDict* const dictPtr = createDict(dictName);

    int u;
    for (u=1; u<argc-1; u++) {
        const char* inFilename = argv[u];
        char* const outFilename = createOutFilename(inFilename);
        compress(inFilename, outFilename, dictPtr);
        free(outFilename);
    }

    printf("All %u files compressed. \n", argc-2);
}