#ifndef lint
static char sccsid[] = "@(#)abspath.c 9.3 88/01/19 Copyright 1984 Sun Micro";
#endif
/*
 * Copyright (c) 1984 by Sun Microsystems, Inc. 
 */

/*-Convert a pathname to an absolute one, if it is absolute already,
   it is returned in the buffer unchanged, otherwise leading "./"s
   will be removed, the name of the current working directory will be
   prepended, and "../"s will be resolved.
  
   In a moment of weakness, I have implemented the cshell ~ filename
   convention.  ~/foobar will have the ~ replaced by the home directory of
   the current user.  ~user/foobar will have the ~user replaced by the
   home directory of the named user.  This should really be in the kernel
   (or be replaced by a better kernel mechanism).  Doing file name
   expansion like this in a user-level program leads to some very
   distasteful non-uniformities.
  
   Another fit of dementia has led me to implement the expansion of shell
   environment variables.  $HOME/mbox is the same as ~/mbox.  If the
   environment variable a = "foo" and b = "bar" then:
	$a	=>	foo
	$a$b	=>	foobar
	$a.c	=>	foo.c
	xxx$a	=>	xxxfoo
	${a}!	=>	foo!
  
   To handle a bizarre remote file name syntax, if a file name begins with 
   '[' abspath won't change it.
 */

#include <sys/types.h>
#ifdef REF
#include <ref/config.h>
#endif
#include <sys/stat.h>
#include <pwd.h>
#include <ctype.h>

static char curwd[200];		/* the current working directory is
				 * remembered here.  chdir()'s are trapped
				 * and this gets updated. */


abspath(nm, buf)		/* input name in nm, absolute pathname
				 * output to buf.  returns -1 if the
				 * pathname cannot be successfully
				 * converted (only happens if the current
				 * directory cannot be found) */
    char       *nm,
               *buf;
{
    register char *s,
               *d;
    char        lnm[1000];
    s = nm;
    d = lnm;
    while (*d++ = *s)
	if (*s++ == '$') {
	    register char *start = d;
	    register    braces = *s == '{';
	    register char *value;
	    while (*d++ = *s)
		if (braces ? *s == '}' : !isalnum(*s))
		    break;
		else
		    s++;
	    *--d = 0;
	    value = (char *) getenv(braces ? start + 1 : start);
	    if (value) {
		for (d = start - 1; *d++ = *value++;);
		d--;
		if (braces && *s)
		    s++;
	    }
	}
    d = buf;
    nm = lnm;
    if (nm[0] == '~')		/* prefix ~ */
	if (nm[1] == '/' || nm[1] == 0)	/* ~/filename */
	    if (s = (char *) getenv("HOME")) {
		if (*++nm)
		    nm++;
	    }
	    else
		s = "";
	else {			/* ~user/filename */
	    register char *nnm;
	    register struct passwd *pw;
	    for (s = nm; *s && *s != '/'; s++);
	    nnm = *s ? s + 1 : s;
	    *s = 0;
	    pw = (struct passwd *) getpwnam(nm + 1);
	    if (pw == 0)
		s = "";
	    else {
		nm = nnm;
		s = pw->pw_dir;
	    }
	}
    else {
	s = curwd;
	if (*s == 0)
	    getwd(curwd);
    }
    while (*d++ = *s++);
    *(d - 1) = '/';
    s = nm;
    if (*s == '/' || *s == '[')
	d = buf;
    while (*d++ = *s++);
    *(d - 1) = '/';
    *d = '\0';
    d = buf;
    s = buf;
    while (*s)
	if ((*d++ = *s++) == '/' && d > buf + 1) {
	    register char *t = d - 2;
	    switch (*t) {
		case '/':	/* found // in the name */
		    --d;
		    break;
		case '.':
		    switch (*--t) {
			case '/':	/* found /./ in the name */
			    d -= 2;
			    break;
			case '.':
			    if (*--t == '/') {	/* found /../ */
				while (t > buf && *--t != '/');
				d = t + 1;
			    }
			    break;
		    }
		    break;
	    }
	}
    if (*(d - 1) == '/' && d > buf + 1)
	d--;
    *d = '\0';
    return 0;
}