/*
 * @(#)path.c	1.1	10/21/84
 *
 * These routines implement a path mechanism for the SUN Gremlin
 * picture editor.  It provides facilities whereby several directories
 * may be searched for files and a defaulting mechanism for file name
 * extensions.
 *
 * Mark Opperman (opcode@monet.BERKELEY)
 *
 */

#include "gremlin.h"
#include <pwd.h>
#include <ctype.h>

/* imports from main.c */

extern char GLibrary[];

/* imports from C */

extern char *strcpy();
extern char *strncpy();
extern char *index();
extern char *sprintf();
extern char *malloc();

/* 
 * The following string holds the current path, consisting of a bunch
 * of directory names separated by spaces.
 */

#define PATHSIZE 400

static char path[PATHSIZE] = ".";

/* 
 * The following string pointers constitute a cache of recently
 * referenced tilde names.
 */

#define NTILDE 10

static char *tildename[NTILDE] = { NULL, NULL, NULL, NULL, NULL,
				   NULL, NULL, NULL, NULL, NULL };
static char *realname[NTILDE]  = { NULL, NULL, NULL, NULL, NULL,
				   NULL, NULL, NULL, NULL, NULL };
static int discard = 0;


/*
 * This routine converts tilde notation into standard directory names.
 *
 * If the conversion was done successfully, then TRUE is returned.
 * If a user name couldn't be found in the password file, then
 * FALSE is returned.
 *
 * If the first character of the string indicated by psource is a
 * tilde ("~") then the subsequent user name is converted to a login
 * directory name and stored in the string indicated by pdest.  Then
 * remaining characters in the file name at psource are copied to
 * pdest and both pointers are updated.  Upon return, psource points
 * to the terminating character in the source file name and pdest
 * points to the next character after the last character in the file
 * name at that location.  If a tilde cannot be converted because the
 * user name cannot be found, psource is still advanced past the current
 * entry, but pdest is unaffected.  At most size characters will be
 * stored at pdest, and the size is decremented by the number of
 * characters we actually stored.
 *
 * mro 7/28/84 
 * fixed NULL pointer bugs
 */
PConvertTilde(psource, pdest, size)
char **psource;		/* Pointer to a pointer to the source string */
char **pdest;		/* Pointer to a pointer to the dest. string */
int *size;		/* Pointer to no. bytes available at pdest */
{
    register char *ps, *pd;
    struct passwd *passwd, *getpwnam();
    char username[17], *string;
    int i, length;

    ps = *psource;
    string = NULL;

    if (*ps == '~') {
	/* Copy the user name into a string (at most 16 characters).  If we 
	   don't have a cached entry for this name, then read the password 
	   file entry for the user and grab out the login directory. */

	pd = username;
	for (i=0; ; i++) {
	    *pd = *++ps;
	    if (isspace(*pd) || (*pd == '\0') || (*pd == '/') || (*pd == ':'))
		break;
	    if (i < 16) 
		pd++;
	}

	*pd = '\0';
	for (i=0;  i<NTILDE; i++) {
	    if (tildename[i] != NULL) {
		if (strcmp(tildename[i], username) == 0) {
		    string = realname[i];
		    break;
		}
	    }
	}

	if (string == NULL) { 			/* didn't find cached entry */
	    passwd = getpwnam(username);	/* check password file */
	    if (passwd != NULL) {		/* got it! */
		string = passwd->pw_dir;
		if (++discard >= NTILDE) 
		    discard = 0;
		if (tildename[discard] != NULL) {
		    free(tildename[discard]);
		    free(realname[discard]);
		}
		tildename[discard] = malloc((unsigned) strlen(username)+1);
		strcpy(tildename[discard], username);
		realname[discard] = malloc((unsigned) strlen(string)+1);
		strcpy(realname[discard], string);
	    }
	    else {				/* illegal user name */
		/* skip the source entry and return */
		while ((*ps != '\0') && !isspace(*ps) && (*ps != ':')) 
		    ps++;
		*psource = ps;
		return(FALSE);
	    }
	}

	length = strlen(string);
	if (length > *size) 
	    length = *size;
	strncpy(*pdest, string, length);
	*size -= length;
	pd = *pdest+length;
    }
    else 
	pd = *pdest;

    /* Copy the rest of the directory name from the source to the dest. */

    while ((*ps != '\0') && !isspace(*ps) && (*ps != ':'))
	if (*size > 0) {
	    *pd++ = *ps++;
	    (*size)--;
	}
	else 
	    ps++;
    *psource = ps;
    *pdest = pd;
    return(TRUE);
}


/*
 * PSetPath sets up the current search path.
 *
 * (-1) is returned if one or more of the paths contained a tilde
 * notation that couldn't be converted.  (-2) is returned if the
 * path space was exhausted.  Otherwise, a value >= 0 is returned.
 *
 * The string is stored as the current path, and all entries with
 * tilde notation are converted to non-tilde notation.  Tilde entries
 * that cannot be converted are ignored.  Note:  only PATHSIZE total
 * bytes of path are stored, after tilde conversion.  Excess bytes
 * are truncated.
 */
PSetPath(string)
char *string;	/* Pointer to a string that is to become the new file 
		   search path.  Must consist of one or more directory 
		   names separated by white space or colons.  Two adjacent 
		   colons are the same as ":.:".  Tilde notation is ok.  */
{
    int result, spaceleft;
    char *p;

    result = 0;
    spaceleft = PATHSIZE-1;
    p = path;

    if (*string == '\0') {
	strcpy(path, ".");
	return(0);
    }
	
    while (*string != '\0') {
	if (*string == ':')
	    if ((*++string == ':') && (spaceleft >= 2)) {
		*p++ = '.';
		*p++ = ' ';
		spaceleft -= 2;
	    }
	if (spaceleft <= 0) 
	    break;
	while ((*string == ':') || isspace(*string)) 
	    string++;
	if (!PConvertTilde(&string, &p, &spaceleft)) 
	    result = -1;
	else if (spaceleft-- > 0) 
	    *p++ = ' ';
    }
    *p = '\0';

    if (spaceleft < 2) 
	return(-2);

    return(result);
}


/*
 *  This routine merely returns a poiner to the current path.
 */
char *
PGetPath()
{
    return(path);
}


/*
 *  This routine does a file lookup using the current path and
 *  supplying a default extension.
 *
 *  Returns a pointer to a FILE, or NULL if the file couldn't be found.
 *
 *  If the first character of the
 *  file name is "~" or "/" or if search is FALSE, then we try
 *  to look up the file with the original name, doing tilde
 *  expansion of course and returning that result.  If none of 
 *  these conditions is met, we go through the current path
 *  trying to look up the file once for each path
 *  entry by prepending the path entry to the original file name.
 *  This concatenated name is stored in a static string and made
 *  available to the caller through prealname if the open succeeds.
 *  Note: the static string will be trashed on the next call to this
 *  routine.  Also, note that no individual file name is allowed to
 *  be more than NAMESIZE characters long.  Excess characters are lost.
 */
FILE *
POpen(file, prealname, search)
char *file;			/* Name of the file to be opened. */
char **prealname;		/* Pointer to a location that will be filled
				   in with the address of the real name of
				   the file that was successfully opened.
				   If NULL, then nothing is stored.  */
int search;			/* If FALSE, then the search path business
				   doesn't happen.  A default extension
				   will still be added.  */
{
#define NAMESIZE 128
    static char realname[NAMESIZE];
    char extendedname[NAMESIZE], *p, *p2;
    int length, spaceleft, size;
    FILE *f;

    if ((file == NULL) || (file[0] == '\0'))
	return((FILE *) NULL);

    if (prealname != NULL) 
	*prealname = realname;

    /* Now try the original name.  If it starts with a ~ or / look 
       it up directly.  */

    if (file[0] == '~') {
	p = realname;
	length = NAMESIZE-1;
	if (!PConvertTilde(&file, &p, &length)) 
	    return(NULL);
	*p = '\0';
	return(fopen(realname, "r"));
    }

    if ((file[0] == '/') || (search == FALSE)) {
	strncpy(realname, file, NAMESIZE-1);
	realname[NAMESIZE-1] = '\0';
	return(fopen(realname, "r"));
    }

    /* Now try going through the path. */

    p = path;
    while (*p != '\0') {
	spaceleft = NAMESIZE-1;
	p2 = realname;
	while (isspace(*p)) 
	    p++;
	while ((*p != '\0') && !isspace(*p)) {
	    if (spaceleft-- > 0) 
		*p2++ = *p++;
	    else 
		p++;
	}
	if (spaceleft-- > 0) 
	    *p2++ = '/';
	if (spaceleft > 0) 
	    strncpy(p2, file, spaceleft);
	realname[NAMESIZE-1] = '\0';
	f = fopen(realname, "r");
	if (f != NULL) {
	    /* if file in current directory fix up prealname */
	    if ((strncmp(realname, "./", 2) == 0) && (prealname != NULL))
		    (*prealname) += 2;
	    return(f);
	}
    }

    /* We've tried the path and that didn't work.  As a last shot,
       try the library area.  Only use the library for reads.  */

    p = GLibrary;
    p2 = realname;
    size = NAMESIZE;
    if (!PConvertTilde(&p, &p2, &size)) 
	return(FALSE);
    (void) strncpy(p2, file, size);
    realname[NAMESIZE-1] = '\0';
    return(fopen(realname, "r"));
}