#include "libshell.h"

char **
getpaths(void)
{
	char *p;
	char **q;
	char *path;
	size_t path_s;
	char *path_temp;
	char **paths;
	size_t paths_s;

	if((path_temp = getenv(PATH_NAME)) == NULL){
		errno = ENOMEM; /* Cannot allocate memory */
		return NULL;
	}

	/* How long is path? */
	for(path_s = 0; path_temp[path_s] != '\0'; ++path_s);
	/* path_s has the size of the path string, not including the null
	 * terminator */

	/* getenv's return value mustn't be modified so copy it into memory we
	 * control */
	if((path = malloc(sizeof(char) * (path_s + 1))) == NULL){
		errno = ENOMEM; /* Cannot allocate memory */
		return NULL;
	}
	memcpy(path, path_temp, path_s + 1);
	path_temp = NULL;
	path_s = 0; /* This shouldn't be necessary anymore */

	/* How many paths in $PATH? */
	for(paths_s = 1, p = path; *p != '\0'; paths_s += *p++ == PATH_DELIMITER);

	if((paths = malloc(sizeof(char *) * (paths_s + 1))) == NULL){
		free(path);
		errno = ENOMEM; /* Cannot allocate memory */
		return NULL;
	}

	/* Replace all instances of the path delimiter with 0, and then put the
	 * next path beginning into paths. */
	/* This way we can get multiple strings out of one span of memory. */
	for(*paths = p = path, q = paths + 1; *p != '\0';)
		if(*p++ == PATH_DELIMITER){
			*(p - 1) = '\0';
			*q++ = p;
		}
	
	paths[path_s] = NULL;

	/* Because paths[0] will always be path, we can just free(*paths) at
	 * the end and discard path */
	path = NULL;

	return paths;
}