#include <stdio.h>

#define UNIX_BREAKS 1
#define PC_BREAKS   2
#define MAC_BREAKS  3
#define DEFAULT_BREAKS PC_BREAKS

/* Define WRITE_MODE as "wb" on PCs */
#define WRITE_MODE  "w"

#define READ_LENGTH 4096;

#define CR 015
#define LF 012
#define HT 011
#define FF 014

/* extern int getopt (int argc, char **argv, char *optstring); */

int main (argc, argv)
int argc;
char **argv;
{
  int  usage (char *, char *);
  int  getopt (int, char **, char*);
  int  lookahead (FILE *f);

  char *infn, *outfn;
  FILE *infile, *outfile;
  char *progname;
  int  breaks = DEFAULT_BREAKS;
  int  verify = 0;
  int  quiet  = 0;
  int  ch;

  char *brname[4] = { "ERROR", "UNIX", "PC", "Mac" };

  unsigned char *inbuf, *outbuf;
  int  inbuflen, outbuflen;
  int  datalen, inplace, outplace;

  extern char *optarg;
  extern int  optind;

  progname = (char *) malloc (strlen(argv[0])+1);
  strcpy(progname, argv[0]);

  while ((ch = getopt(argc, argv, "upmvqhH")) != -1) {
    switch (ch) {
    case 'u': 
      breaks = UNIX_BREAKS;
      break;
    case 'p':
      breaks = PC_BREAKS;
      break;
    case 'm':
      breaks = MAC_BREAKS;
      break;
    case 'v':
      verify = 1;
      break;
    case 'q':
      quiet = 1;
      break;
    case 'h':
    case 'H':
      usage(progname, NULL);
      break;
    default:
      usage(progname, "unexpected option");
    }
  }

  if (optind < argc) {
    infn = argv[optind++];
    if (strcmp(infn, "-") == 0) {
      infile = stdin;
    } else {
      infile = fopen(infn,"r");
    if (infile == NULL)
      usage(progname, "error opening input file");
    }
  } else {
    infn = "-";
    infile = stdin;
  }

  inbuflen = READ_LENGTH;
  outbuflen = 2*inbuflen;

  inbuf = (char *) malloc(inbuflen);
  outbuf = (char *) malloc(outbuflen);

  if (verify) {
    datalen = fread(inbuf, 1, inbuflen, infile);
    ch = 0;
    for (inplace = 0; inplace < datalen; inplace++) {
      if ((inbuf[inplace] < 32) 
	  && (inbuf[inplace] != CR)
	  && (inbuf[inplace] != LF)
	  && (inbuf[inplace] != HT)
	  && (inbuf[inplace] != FF)) {
	ch = 1;
	break;
      }
    }

    if (ch) {
      fprintf (stderr, 
	       "%s: %s does not appear to be a text file (%d).\n", 
	       progname, infn, inplace);
      exit (2);
    }

    fseek(infile, 0, 0);
  }

  if (optind < argc) {
    outfn = argv[optind++];
    if (strcmp(outfn, "-") == 0) {
      outfile = stdout;
    } else {
      outfile = fopen(outfn,WRITE_MODE);
    if (outfile == NULL)
      usage(progname, "error opening output file");
    }
  } else {
    outfn = "-";
    outfile = stdout;
  }

  if (!quiet)
    fprintf (stderr, 
	     "Converting %s to %s with %s line breaks.\n",
	     infn, outfn, brname[breaks]);

  if (strcmp(infn, "-") == 0) {
    /* It's not possible to do random access on a stream, so we have
     * to go slowly through the file.  Another possibility would be creating
     * a temporary file, but how to do that in a system-independent manner?
     */
    int lookch;
    while ((ch = fgetc(infile)) >= 0) {
	/* If this CR is the start of a CR/LF pair, skip it */
	if (ch == CR) {
	  lookch = fgetc(infile);
	  ungetc(lookch, infile);
	  if (lookch == LF)
	    continue;
	}
	    
	if ((ch == CR) || (ch == LF)) {
	  if (breaks == UNIX_BREAKS)
	    fputc(LF, outfile);
	  else
	    fputc(CR, outfile);
	  if (breaks == PC_BREAKS) 
	    fputc(LF, outfile);
	} else {
	  fputc(ch, outfile);
	}
      }
  } else {
    while ((datalen = fread(inbuf, 1, inbuflen, infile)) > 0) {
      outplace = 0;
      for (inplace = 0; inplace < datalen; inplace++) {
	
	/* If this CR is the start of a CR/LF pair, skip it */
	if (inbuf[inplace] == CR) {
	  if (inplace+1 == datalen) {
	    if (lookahead(infile) == LF) 
	      continue;
	  } else {
	    if (inbuf[inplace+1] == LF)
	      continue;
	  }
	}
	    
	if ((inbuf[inplace] == CR) || (inbuf[inplace] == LF)) {
	  if (breaks == UNIX_BREAKS)
	    outbuf[outplace++] = LF;
	  else
	    outbuf[outplace++] = CR;
	  if (breaks == PC_BREAKS) 
	    outbuf[outplace++] = LF;
	} else {
	  outbuf[outplace++] = inbuf[inplace];
	}
      }
      
      datalen = fwrite(outbuf, 1, outplace, outfile);
      if (datalen != outplace) 
	exit(1);
    }
  }

  fclose (infile);
  fclose (outfile);

  exit (0);
}

int usage (progname, msg)
char *progname;
char *msg;
{
  if (msg)
    fprintf (stderr, "Error: %s\n", msg);

  fprintf (stderr, "Usage: %s infile [outfile]\n", progname);
  fprintf (stderr, "Where: infile = name of input file\n");
  fprintf (stderr, "       outfile = name of output file\n");
  fprintf (stderr, "       Use '-' for stdin or stdout, respectively.\n");
  exit (1);
}

int lookahead (f)
FILE *f;
{
  int pos = ftell(f);
  int ch  = fgetc(f);
  fseek(f, pos, 0);

  return ch;
}