use cap_fs_ext::DirExt;
use cap_std::fs::Dir;
use std::ffi::OsString;
use std::io;
use std::path::{Component, Path, PathBuf};

pub fn parent(path: &Path) -> io::Result<(Dir, OsString)> {
    let mut root = PathBuf::new();
    let mut names = Vec::new();
    for component in path.components() {
        match component {
            Component::Prefix(_) | Component::RootDir => root.push(component.as_os_str()),
            Component::Normal(name) => names.push(name),
            _ => {
                return Err(io::Error::new(
                    io::ErrorKind::InvalidInput,
                    "Expected a resolved filesystem path",
                ));
            }
        }
    }
    let name = names.pop().unwrap_or_else(|| std::ffi::OsStr::new("."));
    let mut directory = Dir::open_ambient_dir(root, cap_std::ambient_authority())?;
    for name in names {
        directory = match directory.open_dir_nofollow(name) {
            Ok(directory) => directory,
            Err(_)
                if directory
                    .symlink_metadata(name)
                    .is_ok_and(|metadata| metadata.is_symlink()) =>
            {
                return Err(io::Error::new(
                    io::ErrorKind::NotFound,
                    "Symbolic link changed or has a missing target",
                ));
            }
            Err(error) => return Err(error),
        };
    }
    Ok((directory, name.to_owned()))
}