/* $OpenBSD: gnum4.c,v 1.5 2000/03/11 15:54:44 espie Exp $ */

/*
 * Copyright (c) 1999 Marc Espie
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* 
 * functions needed to support gnu-m4 extensions, including a fake freezing
 */

#include <sys/param.h>
#include <sys/types.h>
#include <ctype.h>
#include <regex.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include "mdef.h"
#include "stdd.h"
#include "extern.h"


int mimic_gnu = 0;

/*
 * Support for include path search
 * First search in the the current directory.
 * If not found, and the path is not absolute, include path kicks in.
 * First, -I options, in the order found on the command line.
 * Then M4PATH env variable
 */

struct path_entry {
	char *name;
	struct path_entry *next;
} *first, *last;

static struct path_entry *new_path_entry __P((const char *));
static void ensure_m4path __P((void));
static struct input_file *dopath __P((struct input_file *, const char *));

static struct path_entry *
new_path_entry(dirname)
	const char *dirname;
{
	struct path_entry *n;

	n = malloc(sizeof(struct path_entry));
	if (!n)
		errx(1, "out of memory");
	n->name = strdup(dirname);
	if (!n->name)
		errx(1, "out of memory");
	n->next = 0;
	return n;
}
	
void 
addtoincludepath(dirname)
	const char *dirname;
{
	struct path_entry *n;

	n = new_path_entry(dirname);

	if (last) {
		last->next = n;
		last = n;
	}
	else
		last = first = n;
}

static void
ensure_m4path()
{
	static int envpathdone = 0;
	char *envpath;
	char *sweep;
	char *path;

	if (envpathdone)
		return;
	envpathdone = TRUE;
	envpath = getenv("M4PATH");
	if (!envpath) 
		return;
	/* for portability: getenv result is read-only */
	envpath = strdup(envpath);
	if (!envpath)
		errx(1, "out of memory");
	for (sweep = envpath; 
	    (path = strsep(&sweep, ":")) != NULL;)
	    addtoincludepath(path);
	free(envpath);
}

static
struct input_file *
dopath(i, filename)
	struct input_file *i;
	const char *filename;
{
	char path[MAXPATHLEN];
	struct path_entry *pe;
	FILE *f;

	for (pe = first; pe; pe = pe->next) {
		snprintf(path, sizeof(path), "%s/%s", pe->name, filename);
		if ((f = fopen(path, "r")) != 0) {
			set_input(i, f, path);
			return i;
		}
	}
	return NULL;
}

struct input_file *
fopen_trypath(i, filename)
	struct input_file *i;
	const char *filename;
{
	FILE *f;

	f = fopen(filename, "r");
	if (f != NULL) {
		set_input(i, f, filename);
		return i;
	}
	if (filename[0] == '/')
		return NULL;

	ensure_m4path();

	return dopath(i, filename);
}

void 
doindir(argv, argc)
	const char *argv[];
	int argc;
{
	ndptr p;

	p = lookup(argv[2]);
	if (p == NULL)
		errx(1, "undefined macro %s", argv[2]);
	argv[1] = p->defn;
	if (p->type == MACRTYPE)
		expand(argv+1, argc-1);
	else
		eval(argv+1, argc-1, p->type);
}

void 
dobuiltin(argv, argc)
	const char *argv[];
	int argc;
{
	int n;
	argv[1] = NULL;
	n = builtin_type(argv[2]);
	if (n != -1)
		eval(argv+1, argc, n);
	else
		errx(1, "unknown builtin %s", argv[2]);
} 


/* We need some temporary buffer space, as pb pushes BACK and substitution
 * proceeds forward... */
static char *buffer;
static size_t bufsize = 0;
static size_t current = 0;

static void addchars __P((const char *, size_t));
static void addchar __P((char));
static char *twiddle __P((const char *));
static char *getstring __P((void));
static void exit_regerror __P((int, regex_t *));
static void do_subst __P((const char *, regex_t *, const char *, regmatch_t *));
static void do_regexpindex __P((const char *, regex_t *, regmatch_t *));
static void do_regexp __P((const char *, regex_t *, const char *, regmatch_t *));
static void add_sub __P((int, const char *, regex_t *, regmatch_t *));
static void add_replace __P((const char *, regex_t *, const char *, regmatch_t *));

static void 
addchars(c, n)
	const char *c;
	size_t n;
{
	if (n == 0)
		return;
	if (current + n > bufsize) {
		if (bufsize == 0)
			bufsize = 1024;
		else
			bufsize *= 2;
		buffer = realloc(buffer, bufsize);
		if (buffer == NULL)
			errx(1, "out of memory");
	}
	memcpy(buffer+current, c, n);
	current += n;
}

static void 
addchar(c)
	char c;
{
	if (current +1 > bufsize) {
		if (bufsize == 0)
			bufsize = 1024;
		else
			bufsize *= 2;
		buffer = realloc(buffer, bufsize);
		if (buffer == NULL)
			errx(1, "out of memory");
	}
	buffer[current++] = c;
}

static char *
getstring()
{
	addchar('\0');
	current = 0;
	return buffer;
}


static void 
exit_regerror(er, re)
	int er;
	regex_t *re;
{
	size_t 	errlen;
	char 	*errbuf;

	errlen = regerror(er, re, NULL, 0);
	errbuf = xalloc(errlen);
	regerror(er, re, errbuf, errlen);
	errx(1, "regular expression error: %s", errbuf);
}

static void
add_sub(n, string, re, pm)
	int n;
	const char *string;
	regex_t *re;
	regmatch_t *pm;
{
	if (n > re->re_nsub)
		warnx("No subexpression %d", n);
	/* Subexpressions that did not match are
	 * not an error.  */
	else if (pm[n].rm_so != -1 &&
	    pm[n].rm_eo != -1) {
		addchars(string + pm[n].rm_so,
			pm[n].rm_eo - pm[n].rm_so);
	}
}

/* Add replacement string to the output buffer, recognizing special
 * constructs and replacing them with substrings of the original string.
 */
static void 
add_replace(string, re, replace, pm)
	const char *string;
	regex_t *re;
	const char *replace;
	regmatch_t *pm;
{
	const char *p;

	for (p = replace; *p != '\0'; p++) {
		if (*p == '&' && !mimic_gnu) {
			add_sub(0, string, re, pm);
			continue;
		}
		if (*p == '\\') {
			if (p[1] == '\\') {
				addchar(p[1]);
				continue;
			}
			if (p[1] == '&') {
				if (mimic_gnu)
					add_sub(0, string, re, pm);
				else
					addchar(p[1]);
				p++;
				continue;
			}
			if (isdigit(p[1])) {
				add_sub(*(++p) - '0', string, re, pm);
				continue;
			}
		}
	    	addchar(*p);
	}
}

static void 
do_subst(string, re, replace, pm)
	const char *string;
	regex_t *re;
	const char *replace;
	regmatch_t *pm;
{
	int error;
	regoff_t last_match = -1;

	while ((error = regexec(re, string, re->re_nsub+1, pm, 0)) == 0) {

		/* NULL length matches are special... We use the `vi-mode' 
		 * rule: don't allow a NULL-match at the last match
		 * position. 
		 */
		if (pm[0].rm_so == pm[0].rm_eo && pm[0].rm_so == last_match) {
			if (*string == '\0')
				return;
			addchar(*string);
			string++;
			continue;
		}
		last_match = pm[0].rm_so;
		addchars(string, last_match);
		add_replace(string, re, replace, pm);
		string += pm[0].rm_eo;
	}
	if (error != REG_NOMATCH)
		exit_regerror(error, re);
	pbstr(string);
}

static void 
do_regexp(string, re, replace, pm)
	const char *string;
	regex_t *re;
	const char *replace;
	regmatch_t *pm;
{
	int error;
	const char *p;

	switch(error = regexec(re, string, re->re_nsub+1, pm, 0)) {
	case 0: 
		add_replace(string, re, replace, pm);
		pbstr(getstring());
		break;
	case REG_NOMATCH:
		break;
	default:
		exit_regerror(error, re);
	}
}

static void 
do_regexpindex(string, re, pm)
	const char *string;
	regex_t *re;
	regmatch_t *pm;
{
	int error;

	switch(error = regexec(re, string, re->re_nsub+1, pm, 0)) {
	case 0:
		pbunsigned(pm[0].rm_so);
		break;
	case REG_NOMATCH:
		pbnum(-1);
		break;
	default:
		exit_regerror(error, re);
	}
}

/* In Gnu m4 mode, parentheses for backmatch don't work like POSIX 1003.2
 * says. So we twiddle with the regexp before passing it to regcomp.
 */
static char *
twiddle(p)
	const char *p;
{
	/* This could use strcspn for speed... */
	while (*p != '\0') {
		if (*p == '\\' && (p[1] == '(' || p[1] == ')')) {
			addchar(p[1]);
			p+=2;
			continue;
		}
		if (*p == '(' || *p == ')')
			addchar('\\');

		addchar(*p);
		p++;
	}
	return getstring();
}

/* patsubst(string, regexp, opt replacement) */
/* argv[2]: string
 * argv[3]: regexp
 * argv[4]: opt rep
 */
void
dopatsubst(argv, argc)
	const char *argv[];
	int argc;
{
	int error;
	regex_t re;
	regmatch_t *pmatch;

	if (argc <= 3) {
		warnx("Too few arguments to patsubst");
		return;
	}
	error = regcomp(&re, mimic_gnu ? twiddle(argv[3]) : argv[3], 
	    REG_EXTENDED);
	if (error != 0)
		exit_regerror(error, &re);
	
	pmatch = xalloc(sizeof(regmatch_t) * (re.re_nsub+1));
	do_subst(argv[2], &re, argv[4] != NULL ? argv[4] : "", pmatch);
	pbstr(getstring());
	free(pmatch);
	regfree(&re);
}

void
doregexp(argv, argc)
	const char *argv[];
	int argc;
{
	int error;
	regex_t re;
	regmatch_t *pmatch;

	if (argc <= 3) {
		warnx("Too few arguments to patsubst");
		return;
	}
	error = regcomp(&re, mimic_gnu ? twiddle(argv[3]) : argv[3], 
	    REG_EXTENDED);
	if (error != 0)
		exit_regerror(error, &re);
	
	pmatch = xalloc(sizeof(regmatch_t) * (re.re_nsub+1));
	if (argv[4] == NULL)
		do_regexpindex(argv[2], &re, pmatch);
	else
		do_regexp(argv[2], &re, argv[4], pmatch);
	free(pmatch);
	regfree(&re);
}