/* Select <n> random lines from a file and print them.
 *
 * SRE, Fri Jun 13 08:17:53 2008 [Janelia]
 * SVN $Id$
 */
#include "esl_config.h"

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

#include "easel.h"
#include "esl_getopts.h"
#include "esl_random.h"

static ESL_OPTIONS options[] = {
  /* name           type      default  env  range toggles reqs incomp  help                                       docgroup*/
  { "-h",        eslARG_NONE,   FALSE,  NULL, NULL,  NULL,  NULL, NULL, "show brief help on version and usage",             1 },
  { "--seed",    eslARG_INT,      "0",  NULL, NULL,  NULL,  NULL, NULL, "set random number generator's seed to <n>",        1 },
  {  0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
};
static char usage[]  = "[-options] <n> <file>";
static char banner[] = "select n lines randomly from a file";

static void
cmdline_failure(char *argv0, char *format, ...)
{
  va_list argp;

  va_start(argp, format);
  vfprintf(stderr, format, argp);
  va_end(argp);
  esl_usage(stdout, argv0, usage);
  printf("\nTo see more help on available options, do %s -h\n\n", argv0);
  exit(1);
}

static void
cmdline_help(char *argv0, ESL_GETOPTS *go) 
{
  esl_banner(stdout, argv0, banner);
  esl_usage (stdout, argv0, usage);
  puts("\n where general options are:");
  esl_opt_DisplayHelp(stdout, go, 1, 2, 80);
  exit(0);
}

int
main(int argc, char **argv)
{
  ESL_GETOPTS    *go       = NULL; 
  ESL_RANDOMNESS *r        = NULL;
  int             nselect  = 0;
  char           *filename = NULL;
  FILE           *fp       = NULL;
  char          **larr     = NULL;
  char           *buf      = NULL;
  int             buflen   = 0;
  char           *tmp      = NULL;
  int             i,j;
  int             n;

  /* Parse command line */
  go = esl_getopts_Create(options);
  if (esl_opt_ProcessCmdline(go, argc, argv) != eslOK) cmdline_failure(argv[0], "Failed to parse command line: %s\n", go->errbuf);
  if (esl_opt_VerifyConfig(go)               != eslOK) cmdline_failure(argv[0], "Error in app configuration: %s\n",   go->errbuf);
  if (esl_opt_GetBoolean(go, "-h") )                   cmdline_help(argv[0], go);
  if (esl_opt_ArgNumber(go) != 2)                      cmdline_failure(argv[0], "Incorrect number of command line arguments.\n");

  nselect  = atoi(esl_opt_GetArg(go, 1));
  filename = esl_opt_GetArg(go, 2);

  r = esl_randomness_Create(esl_opt_GetInteger(go, "--seed"));

  if ((larr = malloc(sizeof(char *) * nselect)) == NULL) esl_fatal("allocation failed");

  if (strcmp(filename, "-") == 0) fp = stdin;
  else {
    if ((fp = fopen(filename, "r")) == NULL) esl_fatal("Failed to open file %s\n", filename);
  }
   
   n = 0;
   while (esl_fgets(&buf, &buflen, fp) == eslOK)
     {
       n++;
       i = esl_rnd_Roll(r, n);
       if (i < nselect) {
	 for (j = i; j < nselect && j < n; j++)
	   {
	     tmp     = larr[j];
	     larr[j] = buf;
	     buf     = tmp;
	   }
	 free(buf);
	 buf    = NULL;
	 buflen = 0; 
       }
     }  

   for (i = 0; i < nselect; i++) printf("%s", larr[i]);

   if (fp != stdin) fclose(fp);
   for (i = 0; i < nselect; i++) free(larr[i]);
   free(larr);
   free(buf);
   esl_randomness_Destroy(r);
   esl_getopts_Destroy(go);
   return 0;
}

/*****************************************************************
 * Easel - a library of C functions for biological sequence analysis
 * Version h3.0; March 2010
 * Copyright (C) 2010 Howard Hughes Medical Institute.
 * Other copyrights also apply. See the COPYRIGHT file for a full list.
 * 
 * Easel is distributed under the Janelia Farm Software License, a BSD
 * license. See the LICENSE file for more details.
 *****************************************************************/