/* flook.c -- implements flook.h */
#include "flook.h"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#include "defines.h"
#include "fileio.h"


/*	possible names and paths of help files under different OSs	*/
const char *pathname[] = {
#if	BSD | USG
	".emacsrc",
	"emacs.hlp",
#if	PKCODE
	"/usr/global/lib/", "/usr/local/bin/", "/usr/local/lib/",
#endif
	"/usr/local/", "/usr/lib/", ""
#endif
} ;

#define PATHNAME_SIZE (sizeof pathname / sizeof pathname[ 0])


/*
 * does <fname> exist on disk?
 *
 * char *fname;     file to check for existance
 */
boolean fexist( const char *fname)
{
    FILE *fp;

    /* try to open the file for reading */
    fp = fopen(fname, "r");

    /* if it fails, just return false! */
    if (fp == NULL)
        return FALSE;

    /* otherwise, close it and report true */
    fclose(fp);
    return TRUE;
}

/*
 * Look up the existance of a file along the normal or PATH
 * environment variable. Look first in the HOME directory if
 * asked and possible
 *
 * char *fname;		base file name to search for
 * boolean hflag;		Look in the HOME environment variable first?
 */
char *flook( const char *fname, boolean hflag)
{
	unsigned i ;	/* index */
	int len ;
	static char fspec[NSTRING];	/* full path spec to search */

#if	ENVFUNC
	char *path;	/* environmental PATH variable */
#endif

	len = sizeof fspec - strlen( fname) - 1 ;
	if( len < 0)
		return NULL ;

#if	ENVFUNC
	if (hflag) {
		char *home;	/* path to home directory */

		home = getenv("HOME");
		if (home != NULL) {
			if( len > (int) strlen( home) + 1) {
			/* build home dir file spec */
				strcpy( fspec, home) ;
				strcat(fspec, "/");
				strcat(fspec, fname);

			/* and try it out */
				if( fexist( fspec))
					return fspec ;
			}
		}
	}
#endif

	/* always try the current directory first */
	if( len >= 0) {
		strcpy( fspec, fname) ;
		if( fexist( fspec))
			return fspec ;
	}

#if	ENVFUNC
#if	USG | BSD
#define	PATHCHR	':'
#else
#define	PATHCHR	';'
#endif

	/* get the PATH variable */
	path = getenv("PATH");
	if (path != NULL)
		while (*path) {
			char *sp;	/* pointer into path spec */
			int cnt ;

			cnt = len ;
			/* build next possible file spec */
			sp = fspec;
			while( *path && (*path != PATHCHR)) {
				if( cnt-- > 0)
					*sp++ = *path ;

				path += 1 ;
			}

			if( cnt >= 0) {
			/* add a terminating dir separator if we need it */
				if (sp != fspec)
					*sp++ = '/';
				*sp = 0;
				strcat(fspec, fname);

			/* and try it out */
				if( fexist( fspec))
					return fspec ;
			}

			if (*path == PATHCHR)
				++path;
		}
#endif

	/* look it up via the old table method */
	for( i = 2; i < PATHNAME_SIZE ; i++)
		if( len >= (int) strlen( pathname[ i])) {
			strcpy( fspec, pathname[ i]) ;
			strcat( fspec, fname);

		/* and try it out */
			if( fexist( fspec))
				return fspec ;
		}

	return NULL;		/* no such luck */
}