/*
 * This helper program generates the set of *.cfg header files, based on a
 * template file and environment variables for the non-constant settings.
 */

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

char *infname;
FILE *inf, *outf;
char include_guard_symbol[32];
char linebuf[256];
int lineno;

make_include_guard_symbol(fname)
	char *fname;
{
	char *sp, *dp;
	int c;

	sp = fname;
	dp = include_guard_symbol;
	*dp++ = '_';
	*dp++ = '_';
	while (c = *sp++) {
		if (islower(c))
			c = toupper(c);
		else if (c == '.')
			c = '_';
		*dp++ = c;
	}
	*dp++ = '_';
	*dp++ = '_';
	*dp = '\0';
}

close_output()
{
	if (outf) {
		fprintf(outf, "#endif /* %s */\n", include_guard_symbol);
		fclose(outf);
		outf = 0;
	}
}

bracket_line()
{
	char *cp;

	close_output();
	cp = index(linebuf+1, ']');
	if (!cp) {
		fprintf(stderr, "%s line %d: unterminated bracket line\n",
			infname, lineno);
		exit(1);
	}
	*cp = '\0';
	outf = fopen(linebuf+1, "w");
	if (!outf) {
		perror(linebuf+1);
		exit(1);
	}
	make_include_guard_symbol(linebuf+1);
	fprintf(outf, "#ifndef %s\n", include_guard_symbol);
	fprintf(outf, "#define %s\n", include_guard_symbol);
}

process_line()
{
	char *cp, *symbol, *value;

	if (linebuf[0] == '[')
		return bracket_line();
	for (cp = linebuf; isspace(*cp); cp++)
		;
	if (*cp == '\0' || *cp == '#')
		return;
	for (symbol = cp; *cp && !isspace(*cp); cp++)
		;
	if (!*cp) {
inv:		fprintf(stderr, "%s line %d: expected two fields\n",
			infname, lineno);
		exit(1);
	}
	*cp++ = '\0';
	while (isspace(*cp))
		cp++;
	if (*cp == '\0' || *cp == '#')
		goto inv;
	for (value = cp; *cp && !isspace(*cp); cp++)
		;
	if (*cp)
		*cp++ = '\0';
	while (isspace(*cp))
		cp++;
	if (*cp != '\0' && *cp != '#')
		goto inv;
	if (!strcmp(value, "var")) {
		value = getenv(symbol);
		if (!value) {
			fprintf(stderr,
			"%s line %d: no environment variable named %s\n",
				infname, lineno, symbol);
			exit(1);
		}
	}
	if (!outf) {
		fprintf(stderr, "%s line %d: no open output file\n",
			infname, lineno);
		exit(1);
	}
	fprintf(outf, "#define %s %s\n", symbol, value);
}

main(argc, argv)
	char **argv;
{
	if (argc != 3) {
		fprintf(stderr, "usage: %s template-file output-dir\n",
			argv[0]);
		exit(1);
	}
	infname = argv[1];
	inf = fopen(infname, "r");
	if (!inf) {
		perror(infname);
		exit(1);
	}
	if (chdir(argv[2]) < 0) {
		perror(argv[2]);
		exit(1);
	}
	for (lineno = 1; fgets(linebuf, sizeof linebuf, inf); lineno++)
		process_line();
	close_output();
	exit(0);
}