/* GNU Mailutils -- a suite of utilities for electronic mail
   Copyright (C) 1999, 2001, 2002 Free Software Foundation, Inc.

   GNU Mailutils 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.

   GNU Mailutils 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 GNU Mailutils; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "mail.h"

/* Scroll directions */
#define D_BWD  -1 /* z- */
#define D_NONE 0  /* z. */
#define D_FWD  1  /* z+ */

/*
 * z [+|-|. [count]]
 * Optional [count] specifies number of pages to skip before
 * displaying from lines. Default is 1.
 * . modifier causes command to redisplay the current page, i.e.
 * starting from the current message.
 */

static int
z_parse_args(int argc, char **argv,
	     unsigned int *return_count, int *return_dir)
{
  int count = 1;
  int mul = 1;
  int dir = D_FWD;
  int an = 0;
  char *argp = NULL;

  argp = &argv[an][1];
  if (*argp == 0)
    {
      an++;
      if (an < argc)
	argp = argv[an];
    }

  if (*argp)
    {
      switch (*argp++)
       {
       case '+':
	 break;
       case '-':
	 dir = D_BWD;
	 break;
       case '.':
	 dir = D_NONE;
	 break;
       default:
	 util_error (_("Bad arguments for the scrolling command"));
	 return 1;
       }

      if (*argp == 0)
	{
	  an++;
	  if (an < argc)
	    argp = argv[an];
	}

      argc -= an;

      if (argc > 1)
	{
	  util_error (_("Too many arguments for the scrolling command"));
	  return 1;
	}

      if (argp && *argp)
	{
	  if (dir == D_NONE)
	    {
	      util_error (_("argument not applicable for z."));
	      return 1;
	    }

	  if ((mul = strtoul (argp, NULL, 10)) == 0)
	    {
	      util_error (_("Bad number of pages"));
	      return 1;
	    }
	}

   }

 *return_count = mul * count;
 *return_dir = dir;

 return 0;
}

int
mail_z (int argc, char **argv)
{
  unsigned int i, nlines;
  unsigned int pagelines = util_screen_lines();
  unsigned int count;
  int dir;
  int crs, end;
  
  if (z_parse_args(argc, argv, &count, &dir))
    return 1;

  nlines = pagelines;

  count *= pagelines;
  crs = cursor;
  switch (dir)
    {
    case D_BWD:
      if (crs < nlines)
	{
	  fprintf (stdout, _("On first screenful of messages\n"));
	  return 0;
	}
      if (crs < count)
	crs = 1;
      else
	crs -= count;
      break;

    case D_FWD:
      if (crs + pagelines > total)
	{
	  fprintf (stdout, _("On last screenful of messages\n"));
	  return 0;
	}

      crs += count;

      if (crs + nlines > total)
	nlines = total - crs + 1;

      if (nlines <= 0)
	{
	  fprintf (stdout, _("On last screenful of messages\n"));
	  return 0;
	}
      break;

    case D_NONE:
      {
	/* z. is a GNU extension, so it will be more useful
	   when we reach the last message to show a full screen
	   of the last message.  This behaviour is used on startup
	   when displaying the summary and the headers, new messages
	   are last but we want to display a screenful with the
	   real crs set by summary() to the new message.  */

	/* Find the start of the last screen page.  */
	int lastpage =  total - pagelines + 1;
	if (lastpage <= 0)
	  lastpage = 1;

	if (crs > (unsigned int)lastpage)
	  {
	    crs = lastpage;

	    if (crs + nlines > total)
	      nlines = total - crs;

	    util_range_msg (crs, crs + nlines,
			    MSG_NODELETED|MSG_SILENT, mail_from0, NULL);
	    return 1;
	  }
	else if (crs + nlines > total)
	  nlines = total - crs + 1;
      }
      break;
    }

  cursor = crs;
  end = cursor + nlines - 1;
  i = 0;
  do
    {
      int cnt = util_range_msg (crs, end,
				MSG_NODELETED|MSG_SILENT, mail_from0, NULL);
      if (cnt == 0)
	break;
      i += cnt;
      crs += nlines;
    }
  while (i < nlines && crs <= total);

  return 1;
}