/*
 * POSIX directory-stream wrappers.
 *
 * opendir(3), fdopendir(3), readdir(3), closedir(3), and rewinddir(3) expose
 * three different failure conventions between them. These wrappers turn all
 * three into error contexts and make end-of-directory an explicit AKERR_EOF.
 */
#include <akstdlib.h>

#include <errno.h>

#include "aksl_internal.h"

/*
 * opendir(3) returns NULL for failure. Clear *dest first so a failed open
 * cannot leave the caller holding a stale directory stream.
 */
akerr_ErrorContext AKERR_NOIGNORE *aksl_opendir(const char *pathname, DIR **dest)
{
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, dest, AKERR_NULLPOINTER, "pathname=%p, dest=%p",
		     (void *)pathname, (void *)dest);
    *dest = NULL;
    FAIL_ZERO_RETURN(e, pathname, AKERR_NULLPOINTER, "pathname=%p, dest=%p",
		     (void *)pathname, (void *)dest);
    errno = 0;
    *dest = opendir(pathname);
    FAIL_ZERO_RETURN(e, *dest, AKSL_ERRNO_OR(AKERR_IO), "pathname=%s", pathname);
    SUCCEED_RETURN(e);
}

/*
 * fdopendir(3) takes ownership of fd only when it succeeds. On success the
 * matching aksl_closedir call closes both the stream and its descriptor.
 */
akerr_ErrorContext AKERR_NOIGNORE *aksl_fdopendir(int fd, DIR **dest)
{
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, dest, AKERR_NULLPOINTER, "fd=%d, dest=%p", fd, (void *)dest);
    *dest = NULL;
    errno = 0;
    *dest = fdopendir(fd);
    FAIL_ZERO_RETURN(e, *dest, AKSL_ERRNO_OR(AKERR_IO), "fd=%d", fd);
    SUCCEED_RETURN(e);
}

/*
 * readdir(3) owns and may reuse its returned storage. Copy the entry into the
 * caller's destination, and use errno to distinguish failure from exhaustion.
 */
akerr_ErrorContext AKERR_NOIGNORE *aksl_readdir(DIR *dirp, struct dirent *dest)
{
    struct dirent *entry = NULL;
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, dirp, AKERR_NULLPOINTER, "dirp=%p, dest=%p",
		     (void *)dirp, (void *)dest);
    FAIL_ZERO_RETURN(e, dest, AKERR_NULLPOINTER, "dirp=%p, dest=%p",
		     (void *)dirp, (void *)dest);

    /* readdir uses errno to distinguish failure from end-of-directory. */
    errno = 0;
    entry = readdir(dirp);
    if ( entry == NULL ) {
	FAIL_NONZERO_RETURN(e, errno, AKSL_ERRNO_OR(AKERR_IO), "readdir failed");
	FAIL_RETURN(e, AKERR_EOF, "end of directory");
    }
    *dest = *entry;
    SUCCEED_RETURN(e);
}

/* closedir(3) reports its failure directly and invalidates dirp on success. */
akerr_ErrorContext AKERR_NOIGNORE *aksl_closedir(DIR *dirp)
{
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, dirp, AKERR_NULLPOINTER, "dirp=%p", (void *)dirp);
    errno = 0;
    FAIL_NONZERO_RETURN(e, closedir(dirp), AKSL_ERRNO_OR(AKERR_IO),
			"closedir failed");
    SUCCEED_RETURN(e);
}

/*
 * rewinddir(3) has no failure return. Preserve that contract after rejecting
 * a NULL stream, which would otherwise be undefined behaviour.
 */
akerr_ErrorContext AKERR_NOIGNORE *aksl_rewinddir(DIR *dirp)
{
    PREPARE_ERROR(e);
    FAIL_ZERO_RETURN(e, dirp, AKERR_NULLPOINTER, "dirp=%p", (void *)dirp);
    rewinddir(dirp);
    SUCCEED_RETURN(e);
}