/* comm -- compare two sorted files line by line.
   Copyright (C) 1986, 1990, 1991 Free Software Foundation, Inc.

   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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* Written by Richard Stallman and David MacKenzie. */

#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>
#include "system.h"
#include "linebuffer.h"

#define min(x, y) ((x) < (y) ? (x) : (y))

/* If nonzero, print lines that are found only in file 1. */
int only_file_1;

/* If nonzero, print lines that are found only in file 2. */
int only_file_2;

/* If nonzero, print lines that are found in both files. */
int both;

/* The name this program was run with. */
char *program_name;

int compare_files ();
void error ();
void writeline ();
void usage ();

void
main (argc, argv)
     int argc;
     char *argv[];
{
  int c;

  program_name = argv[0];

  only_file_1 = 1;
  only_file_2 = 1;
  both = 1;

  while ((c = getopt (argc, argv, "123")) != EOF)
    switch (c)
      {
      case '1':
	only_file_1 = 0;
	break;

      case '2':
	only_file_2 = 0;
	break;

      case '3':
	both = 0;
	break;

      default:
	usage ();
      }

  if (optind + 2 != argc)
    usage ();

  exit (compare_files (argv + optind));
}

/* Compare INFILES[0] and INFILES[1].
   If either is "-", use the standard input for that file.
   Assume that each input file is sorted;
   merge them and output the result.
   Return 0 if successful, 1 if any errors occur. */

int
compare_files (infiles)
     char **infiles;
{
  /* For each file, we have one linebuffer in lb1.  */
  struct linebuffer lb1[2];

  /* thisline[i] points to the linebuffer holding the next available line
     in file i, or is NULL if there are no lines left in that file.  */
  struct linebuffer *thisline[2];

  /* streams[i] holds the input stream for file i.  */
  FILE *streams[2];

  int i, ret = 0;

  /* Initialize the storage. */
  for (i = 0; i < 2; i++)
    {
      initbuffer (&lb1[i]);
      thisline[i] = &lb1[i];
      streams[i] = strcmp (infiles[i], "-")
	? fopen (infiles[i], "r") : stdin;
      if (!streams[i])
	{
	  error (0, errno, "%s", infiles[i]);
	  return 1;
	}

      thisline[i] = readline (thisline[i], streams[i]);
    }

  while (thisline[0] || thisline[1])
    {
      int order;

      /* Compare the next available lines of the two files.  */

      if (!thisline[0])
	order = 1;
      else if (!thisline[1])
	order = -1;
      else
	{
	  /* Cannot use bcmp -- it only returns a boolean value. */
	  order = memcmp (thisline[0]->buffer, thisline[1]->buffer,
			  min (thisline[0]->length, thisline[1]->length));
	  if (order == 0)
	    order = thisline[0]->length - thisline[1]->length;
	}

      /* Output the line that is lesser. */
      if (order == 0)
	writeline (thisline[1], stdout, 3);
      else if (order > 0)
	writeline (thisline[1], stdout, 2);
      else
	writeline (thisline[0], stdout, 1);

      /* Step the file the line came from.
	 If the files match, step both files.  */
      if (order >= 0)
	thisline[1] = readline (thisline[1], streams[1]);
      if (order <= 0)
	thisline[0] = readline (thisline[0], streams[0]);
    }

  /* Free all storage and close all input streams. */
  for (i = 0; i < 2; i++)
    {
      free (lb1[i].buffer);
      if (ferror (streams[i]) || fclose (streams[i]) == EOF)
	{
	  error (0, errno, "%s", infiles[i]);
	  ret = 1;
	}
    }
  if (ferror (stdout) || fclose (stdout) == EOF)
    {
      error (0, errno, "write error");
      ret = 1;
    }
  return ret;
}

/* Output the line in linebuffer LINE to stream STREAM
   provided the switches say it should be output.
   CLASS is 1 for a line found only in file 1,
   2 for a line only in file 2, 3 for a line in both. */

void
writeline (line, stream, class)
     struct linebuffer *line;
     FILE *stream;
     int class;
{
  switch (class)
    {
    case 1:
      if (!only_file_1)
	return;
      break;

    case 2:
      if (!only_file_2)
	return;
      /* Skip the tab stop for case 1, if we are printing case 1.  */
      if (only_file_1)
	putc ('\t', stream);
      break;

    case 3:
      if (!both)
	return;
      /* Skip the tab stop for case 1, if we are printing case 1.  */
      if (only_file_1)
	putc ('\t', stream);
      /* Skip the tab stop for case 2, if we are printing case 2.  */
      if (only_file_2)
	putc ('\t', stream);
      break;
    }

  fwrite (line->buffer, sizeof (char), line->length, stream);
  putc ('\n', stream);
}

void
usage ()
{
  fprintf (stderr, "Usage: %s [-123] file1 file2\n", program_name);
  exit (1);
}