use std::fs;
use std::future::Future;
use std::io;
use std::path::Path;
use std::pin::Pin;
use std::task::Context;
use std::task::Poll;

/// Changes the permissions found on a file or a directory.
///
/// This is an async version of [`std::fs::set_permissions`][std]
///
/// [std]: https://doc.rust-lang.org/std/fs/fn.set_permissions.html
pub fn set_permissions<P: AsRef<Path>>(path: P, perm: fs::Permissions) -> SetPermissionsFuture<P> {
    SetPermissionsFuture::new(path, perm)
}

/// Future returned by `set_permissions`.
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct SetPermissionsFuture<P>
where
    P: AsRef<Path>,
{
    path: P,
    perm: fs::Permissions,
}

impl<P> SetPermissionsFuture<P>
where
    P: AsRef<Path>,
{
    fn new(path: P, perm: fs::Permissions) -> SetPermissionsFuture<P> {
        SetPermissionsFuture { path, perm }
    }
}

impl<P> Future for SetPermissionsFuture<P>
where
    P: AsRef<Path>,
{
    type Output = io::Result<()>;

    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
        crate::blocking_io(|| fs::set_permissions(&self.path, self.perm.clone()))
    }
}