/*

 * Copyright (c) 2014, Mathieu Malaterre <mathieu.malaterre@voxxl.com>

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS `AS IS'

 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 * POSSIBILITY OF SUCH DAMAGE.

 */

/*

 * Technically on UNIX, one can simply call `ppmtorgb3`, but on my system it

 * did not work. So I had to write my own.

 */

#include <stdio.h>  /* fprintf */

#include <string.h> /* strcmp */

#include <stdlib.h> /* malloc */

static const char magic[] = "P6";

static int readheader( FILE *ppm, int *X, int *Y, int *bpp )

{

  char buffer[256];

  char strbuffer[256];

  char *line;

  int n;

  *X = *Y = *bpp = 0;

  line = fgets(buffer, sizeof(buffer), ppm);

  if( !line ) return 0;

  n = sscanf(buffer, "%255[^\r\n]", strbuffer);

  if( n != 1 ) return 0;

  if( strcmp(strbuffer, magic ) != 0 ) return 0;

  /* skip comments */

  while( fgets(buffer, sizeof(buffer), ppm) && *buffer == '#' )

    {

    }

  n = sscanf(buffer, "%d %d", X,Y);

  if( n != 2 ) return 0;

  line = fgets(buffer, sizeof(buffer), ppm);

  if( !line ) return 0;

  n = sscanf(buffer, "%d", bpp);

  if( n != 1 ) return 0;

  if( *bpp != 255 ) return 0;

  return 1;

}

static int writeoutput( const char *fn, FILE *ppm, int X, int Y, int bpp )

{

  FILE *outf[] = {NULL, NULL, NULL};

  int i, x, y = 0;

  char outfn[256];

  static const char *exts[3] = {

    "red",

    "grn",

    "blu"

  };

  char *image_line = NULL;

  int ok = 0;

  /* write single comp as PGM: P5 */

  for( i = 0; i < 3; ++i )

    {

#ifdef _MSC_VER

#define snprintf _snprintf /* Visual Studio */

#endif

    snprintf( outfn, sizeof(outfn), "%s.%s.pgm", fn, exts[i] );

    outf[i] = fopen( outfn, "wb" );

    if( !outf[i] ) goto cleanup;

    /* write header */

    fprintf( outf[i], "P5\n" );

    fprintf( outf[i], "%d %d\n", X, Y );

    fprintf( outf[i], "%d\n", bpp );

    }

  /* write pixel data */

  image_line = (char*)malloc( (size_t)X * 3 * sizeof(char) );

  if( !image_line ) goto cleanup;

  while( fread(image_line, sizeof(char), (size_t)X * 3, ppm) == (size_t)X * 3 )

    {

    for( x = 0; x < X; ++x )

      for( i = 0; i < 3; ++i )

        if( fputc( image_line[3*x+i], outf[i] ) == EOF ) goto cleanup;

    ++y;

    }

  if( y == Y )

    ok = 1;

cleanup:

  free(image_line);

  for( i = 0; i < 3; ++i )

    if( outf[i] ) fclose( outf[i] );

  return ok;

}

int main(int argc, char *argv[])

{

  const char *fn;

  FILE *ppm = NULL;

  int X, Y, bpp;

  int ok = 0;

  if( argc < 2 )

    {

    fprintf( stderr, "%s input.ppm\n", argv[0] );

    goto cleanup;

    }

  fn = argv[1];

  ppm = fopen( fn, "rb" );

  if( !readheader( ppm, &X, &Y, &bpp ) ) goto cleanup;

  if( !writeoutput(fn, ppm, X, Y, bpp ) ) goto cleanup;

  ok = 1;

cleanup:

  if(ppm) fclose(ppm);

  return ok ? EXIT_SUCCESS : EXIT_FAILURE;

}