use super::open_parent;
use crate::fs::{read_link_unchecked, MaybeOwnedFile};
use std::{
    fs, io,
    path::{Path, PathBuf},
};

/// Implement `read_link` by `open`ing up the parent component of the path and
/// then calling `read_link_unchecked` on the last component.
///
/// Note that this technique doesn't work in all cases on Windows. In
/// particular, a directory symlink such as `C:\Documents and Settings` may not
/// grant any access other than what is needed to resolve the symlink, so
/// `open_parent`'s technique of returning a relative path of `.` from that
/// point doesn't work, because opening `.` within such a directory is denied.
/// Consequently, we use a different implementation on Windows.
pub(crate) fn read_link(start: &fs::File, path: &Path) -> io::Result<PathBuf> {
    let start = MaybeOwnedFile::borrowed(start);

    let (dir, basename) = open_parent(start, path)?;

    read_link_unchecked(&dir, basename.as_ref(), PathBuf::new())
}
