/*
*
*	env /bin/python2.4 ...
*	or simply
*	env python2.4 ...
*	then "env" reads namespace file "/sys/lib/env/python2.4"
*
*	env is designed to be used in the first line in the executables
*		#!/bin/env paython2.4
*/

#include <u.h>
#include <libc.h>
#include <bio.h>
int atime = 0;

static void nsop(int argc, char *argv[]);


void
usage(void)
{
	fprint(2,"usage: env [-a time] path arg ...\n");
	exits("usage");
}


/*	bind only addns
*	original source: /sys/src/libauth/newns.c	*/
#define NARG	5
int
chgns(char *file)
{
	Biobuf *spec;
	int argc;
	char *cmd, *argv[NARG];

	spec = Bopen(file, OREAD);
	if(spec == 0)
		return -1;

	while(cmd = Brdline(spec, '\n')){
		cmd[Blinelen(spec)-1] = '\0';
		while(*cmd==' ' || *cmd=='\t')
			cmd++;
		if(*cmd == '#')
			continue;
		/* we need not support '#' tree	*/
		argc = getfields(cmd, argv, NARG, 1, " \t");
		if(argc)
			nsop(argc, argv);
	}
	Bterm(spec);
	return 0;
}

/* 	bind only nsop
*	original source: /sys/src/libauth/newns.c	*/
static void
nsop(int argc, char *argv[])
{
	char *argv0;
	ulong flags;

	flags = 0;
	argv0 = 0;
	ARGBEGIN{
	case 'a':
		flags |= MAFTER;
		break;
	case 'b':
		flags |= MBEFORE;
		break;
	case 'c':
		flags |= MCREATE;
		break;
	case 'C':
		// flags |= MCACHE;
		break;
	}ARGEND

	if(!(flags & (MAFTER|MBEFORE)))
		flags |= MREPL;
	if(strcmp(argv0, "bind") == 0 && argc == 2)
		bind(argv[0], argv[1], flags);
	else if(strcmp(argv0, "cd") == 0 && argc == 1)
		chdir(argv[0]);
}

void
main(int argc, char *argv[])
{
	char *ns, *path, *p, *q;
	int n;

	ARGBEGIN{
	case 'a':
		atime = atoi(EARGF(usage())); // alarm time
		break;
	default: usage();
	}ARGEND


	path = argv[0];
	if(path == nil)
		usage();

	/*	path is /bin/python2.4 */
	p = strrchr(path,'/');
	if(p == nil){
		n = strlen(path)+10;
		q = malloc(n);
		snprint(q, n, "/bin/%s", path);
		p = path;
		path = q;
	}

	n = strlen(p)+20;
	ns = malloc(n);
	snprint(ns, n, "/sys/lib/env/%s", p);

	chgns(ns);

	if(atime)
		alarm(1000*atime);
	if(*argv)
		exec(path, argv);
}