/*
 *	aegis - project change supervisor
 *	Copyright (C) 1999, 2001 Peter Miller;
 *	All rights reserved.
 *
 *	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 of the License, 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., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 * MANIFEST: functions to manipulate quotes
 */

#include <ac/ctype.h>

#include <str.h>
#include <stracc.h>
#include <trace.h>


string_ty *
str_quote_shell(s)
	string_ty	*s;
{
	const char	*cp;
	int		needs_quoting;
	static stracc_t	buffer;
	int		mode;

	/*
	 * Convert the work list to a single string.
	 */
	trace(("str_quote()\n{\n"));

	/*
	 * Work out if the string needs quoting.
	 *
	 * The empty string is not quoted, even though it could be argued
	 * that it needs to be.  It has proven more useful in the present
	 * form, because it allows empty filename lists to pass through
	 * and remain empty.
	 */
	needs_quoting = 0;
	mode = 0;
	for (cp = s->str_text; *cp; ++cp)
	{
		if (isspace(*cp))
		{
			needs_quoting = 1;
			break;
		}
		switch (*cp)
		{
		default:
			continue;

		case '!':
			/* special for bash and csh */
			if (!mode)
				mode = '\'';
			needs_quoting = 1;
			break;

		case '\'':
			if (!mode)
				mode = '"';
			needs_quoting = 1;
			break;

		case '"': case '#': case '$': case '&':
		case '(': case ')': case '*': case ':': case ';': case '<':
		case '=': case '>': case '?': case '[': case '\\': case ']':
		case '^': case '`': case '{': case '|': case '}': case '~':
			needs_quoting = 1;
			break;
		}
		break;
	}

	/*
	 * If it doesn't need quoting, return immediately.
	 */
	if (!needs_quoting)
	{
		s = str_copy(s);
		trace(("return %8.8lX;\n", (long)s));
		trace(("}\n"));
		return s;
	}

	/*
	 * If we have a choice, use single quote mode,
	 * it's shorter and easier to read.
	 */
	if (!mode)
		mode ='\'';

	/*
	 * Form the quoted string, using the minimum number of escapes.
	 *
	 * The gotcha here is the backquote: the `blah` substitution is
	 * still active within double quotes.  And so are a few others. 
	 *
	 * Also, there are some difficulties: the single quote can't be
	 * quoted within single quotes, and the exclamation mark can't
	 * be quoted by anything *except* single quotes.  Sheesh.
	 *
	 * Also, the rules change depending on which style of quoting
	 * is in force at the time.
	 */
	stracc_open(&buffer);
	stracc_char(&buffer, mode);
	for (cp = s->str_text; *cp; ++cp)
	{
		if (mode == '\'')
		{
			/* within single quotes */
			if (*cp == '\'')
			{
				/*
				 * You can't quote a single quote within
				 * single quotes.  Need to change to
				 * double quote mode.
				 */
				stracc_chars(&buffer, "'\"'", 3);
				mode = '"';
			}
			else
				stracc_char(&buffer, *cp);
		}
		else
		{
			/* within double quotes */
			switch (*cp)
			{
			case '!':
				/*
				 * You can't quote an exclamation mark
				 * within double quotes.  Need to change
				 * to single quote mode.
				 */
				stracc_chars(&buffer, "\"'!", 3);
				mode = '\'';
				break;

			case '\n':
			case '"':
			case '\\':
			case '`': /* stop command substitutions */
			case '$': /* stop variable substitutions */
				stracc_char(&buffer, '\\');
				/* fall through... */

			default:
				stracc_char(&buffer, *cp);
				break;
			}
		}
	}
	stracc_char(&buffer, mode);
	s = stracc_close(&buffer);

	/*
	 * all done
	 */
	trace(("return %8.8lX;\n", (long)s));
	trace(("}\n"));
	return s;
}