/*
 * Copyright Daniel Silverstone <dsilvers@digital-scurf.org> 2006
 */

#include "config.h"

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#include "libgfshare.h"

#define BUFFER_SIZE 4096

#ifndef MIN
#define MIN(a,b) ((a)<(b))?(a):(b)
#endif

static char* progname;

void
usage(FILE* stream)
{
  fprintf( stream, "\
Usage: %s [-o outputfile] inputfile inputfile2...\n\
  where outputfile is the filename to write the combined result to.\n\
  where inputfile[2...] are the shares to recombine.\n\
\n\
If outputfile is not provided, it is automatically created by stripping the\n\
last four characters off the first input file name.\n\
\n\
Each input file must be the same length and the filenames must end in a\n\
number which will be taken to be the share number. I.E. \".NNN\".\n\
", progname );
}

static unsigned int
getlen( FILE* f )
{
  unsigned int len;
  fseek(f, 0, SEEK_END);
  len = ftell(f);
  fseek(f, 0, SEEK_SET);
  return len;
}

static void
bad_filename( char* fname )
{
  fprintf( stderr, "%s: %s: bad filename\nInput files should be called <name>.NNN\n", progname, fname );
}

static int
check_filenames( char **filenames, int count )
{
  int i;
  if( count < 2 ) {
    fprintf(stderr, "%s: Insufficient input files. (Min of 2 for recombination)\n", progname);
    return 1;
  }
  for( i = 0; i < count; ++i ) {
    int nlen = strlen(filenames[i]);
    if( nlen < 5 ) {
      bad_filename(filenames[i]);
      return 1;
    }
    if( filenames[i][nlen-4] != '.' ||
        !isdigit(filenames[i][nlen-3]) ||
        !isdigit(filenames[i][nlen-2]) ||
        !isdigit(filenames[i][nlen-1]) ) {
      bad_filename(filenames[i]);
      return 1;
    }
  }
  return 0;
}

static int
do_gfcombine( char *outputfilename, char **inputfilenames, int filecount )
{
  FILE *outfile;
  FILE **inputfiles = malloc( sizeof(FILE*) * filecount );
  unsigned char* sharenrs = malloc( filecount );
  int i;
  unsigned char *buffer = malloc( BUFFER_SIZE );
  gfshare_ctx *G;
  unsigned int len1;
  
  outfile = fopen( outputfilename, "wb" );
  if( outfile == NULL ) {
    perror(outputfilename);
    return 1;
  }
  for( i = 0; i < filecount; ++i ) {
    inputfiles[i] = fopen( inputfilenames[i], "rb" );
    if( inputfiles[i] == NULL ) {
      perror(inputfilenames[i]);
      return 1;
    }
    sharenrs[i] = strtoul( inputfilenames[i] + strlen(inputfilenames[i]) - 3, 
                           NULL, 10 );
    if( i == 0 ) len1 = getlen(inputfiles[0]);
    else {
      if( len1 != getlen(inputfiles[1]) ) {
        fprintf( stderr, "%s: File length mismatch between input files.\n", progname );
        return 1;
      }
    }
  }
  
  G = gfshare_ctx_init_dec( sharenrs, filecount, BUFFER_SIZE );
  
  while( !feof(inputfiles[0]) ) {
    unsigned int bytes_read = fread( buffer, 1, BUFFER_SIZE, inputfiles[0] );
    unsigned int bytes_written;
    gfshare_ctx_dec_giveshare( G, 0, buffer );
    for( i = 1; i < filecount; ++i ) {
      unsigned int bytes_read_2 = fread( buffer, 1, BUFFER_SIZE, 
                                         inputfiles[i] );
      if( bytes_read != bytes_read_2 ) {
        fprintf( stderr, "Mismatch during file read.\n");
        gfshare_ctx_free( G );
        return 1;
      }
      gfshare_ctx_dec_giveshare( G, i, buffer );
    }
    gfshare_ctx_dec_extract( G, buffer );
    bytes_written = fwrite( buffer, 1, bytes_read, outfile );
    if( bytes_written != bytes_read ) {
      fprintf( stderr, "Mismatch during file write.\n");
      gfshare_ctx_free( G );
      return 1;
    }
  }
  fclose(outfile);
  for( i = 0; i < filecount; ++i ) fclose(inputfiles[i]);
  return 0;
}

#define OPTSTRING "o:hv"
int
main( int argc, char **argv )
{
  int optnr;
  char *outputfile = NULL;
  
  progname = argv[0];
  
  while( (optnr = getopt(argc, argv, OPTSTRING)) != -1 ) {
    switch( optnr ) {
    case 'v':
      fprintf( stdout, "%s", "\
gfcombine (" PACKAGE_STRING ")\n\
Written by Daniel Silverstone.\n\
\n\
Copyright (C) 2006 Daniel Silverstone <dsilvers@digital-scurf.org>\n\
This is free software; see the source for copying conditions.  There is NO\n\
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
" );
      return 0;
      break;
    case 'h':
      fprintf( stdout, "%s", "gfcombine (" PACKAGE_STRING ")\n");
      usage( stdout );
      return 0;
      break;
    case 'o':
      outputfile = optarg;
      break;
    }
  }
  
  if( check_filenames(argv+optind, argc-optind) ) return 1;
  
  if( outputfile == NULL ) {
    outputfile = strdup(argv[optind]);
    outputfile[strlen(outputfile)-4] = 0;
  }
  
  return do_gfcombine(outputfile, argv+optind, argc-optind);
}