/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2020 Baptiste Daroussin <bapt@FreeBSD.org>
 *
 * 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 AUTHOR 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>

#include <ctype.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define NELEMS(a) (sizeof(a) / sizeof(a[0]))

static const char *
parse_config(const char *conffile, const char *cctype)
{
	FILE *conf;
	char *line = NULL;
	size_t linecap = 0;
	ssize_t linelen;
	char *walk, *value;
	int confline = 0;
	char ccpathbuf[MAXPATHLEN];
	const char *ccpath = NULL;
	
	if ((conf = fopen(conffile, "r")) == NULL)
		return (NULL);

	while ((linelen = getline(&line, &linecap, conf)) > 0) {
		confline++;
		walk = line;
		walk += strspn(walk, " \t\n\r");
		if (*walk == '\0')
			continue;
		/* consider # as a comment line */
		if (*walk == '#')
			continue;

		value = strchr(walk, '=');
		if (value == NULL)
			value = strchr(walk, ':');
		if (value == NULL)
			errx(1, "Malformed line in the configuration file: %s line: %d",
			    conffile, confline);

		*value = '\0';
		value++;

		/* ignore lines not concernant if cctype we are looking for */
		if (strncmp(walk, cctype, strlen(cctype)) != 0)
			continue;
		walk += strlen(cctype);

		/*
		 * allow space and tabs after the key, if anything else if found, then
		 * skip the line we consider the key not to be our cctype
		 */
		if (strspn(walk, " \t") != strlen(walk))
			continue;

		value += strspn(value, " \t");
		if (*value == '\0' || *value == '\n')
			errx(1, "Invalid value for %s, line %d in the configuration file %s",
			    cctype, confline, conffile);

		/* trim space an the end of the value */
		walk = value + strlen(value) - 1;
		while (walk > value && isspace(*walk)) {
			*walk = '\0';
			walk--;
		}
		strlcpy(ccpathbuf, value, MAXPATHLEN);
		ccpath = ccpathbuf;
		break;
	}

	free(line);
	fclose(conf);
	return (ccpath);
}

static const char *
get_cc_from_config(const char *cctype)
{
	char confpath[MAXPATHLEN];
	unsigned int i;
	const char *confpaths[] = {
		NULL,
		NULL,
		"/etc/compiler.conf",
		"/etc/defaults/compiler.conf",
	};
	const char *ccpath;
	const char *localbase;

	/*
	 * In order we first try to get the configuration from 
	 * LOCALBASE/etc/compiler.conf then from /etc/compiler.conf
	 * only then we try to fallback on /etc/defaults/compiler.conf
	 */

	localbase = getenv("LOCALBASE");
	if (localbase == NULL)
		localbase = "/usr/local";
	snprintf(confpath, MAXPATHLEN, "%s/etc/compiler.conf", localbase);
	confpaths[1] = getenv("COMPILER_CONF");
	confpaths[0] = confpath;
	for (i = 0; i < NELEMS(confpaths); i++) {
		if (confpaths[i] == NULL)
			continue;
		ccpath = parse_config(confpaths[i], cctype);
		if (ccpath != NULL)
			return (ccpath);
	}

	return (NULL);
}

int
main(int argc __unused, char *argv[])
{
	const char *ccpath = NULL;
	const char *cctype = NULL;
	const char *progname = getprogname();

	if (strcmp(progname, "cc") == 0) {
		cctype = "CC";
	} else if (strcmp(progname, "cpp") == 0) {
		cctype = "CPP";
	} else if (strcmp(progname, "c++") == 0) {
		cctype = "CXX";
	} else {
		errx(1, "Invalid progname, this can only be used as cc, c++ or cpp");
	}
	ccpath = get_cc_from_config(cctype);
	if (ccpath == NULL)
		errx(1, "Unable to determine the value of %s", getprogname());

	execvp(ccpath, argv);
	err(1, "%s", ccpath);
}