#[cfg(unix)]
pub(crate) const FDS_MAX: usize = 1024; // this is hardcoded in sdbus - nothing in the spec

pub(crate) fn padding_for_8_bytes(value: usize) -> usize {
    padding_for_n_bytes(value, 8)
}

pub(crate) fn padding_for_n_bytes(value: usize, align: usize) -> usize {
    let len_rounded_up = value.wrapping_add(align).wrapping_sub(1) & !align.wrapping_sub(1);

    len_rounded_up.wrapping_sub(value)
}

/// Helper trait for macro-generated code.
///
/// This trait allows macros to refer to the `Ok` and `Err` types of a [Result] that is behind a
/// type alias.  This is currently required because the macros for properties expect a Result
/// return value, but the macro-generated `receive_` functions need to refer to the actual
/// type without the associated error.
pub trait ResultAdapter {
    type Ok;
    type Err;
}

impl<T, E> ResultAdapter for Result<T, E> {
    type Ok = T;
    type Err = E;
}

#[cfg(feature = "async-io")]
pub(crate) fn block_on<F: std::future::Future>(future: F) -> F::Output {
    async_io::block_on(future)
}

#[cfg(all(not(feature = "async-io"), feature = "tokio"))]
lazy_static::lazy_static! {
    static ref TOKIO_RT: tokio::runtime::Runtime = {
        tokio::runtime::Builder::new_current_thread()
            .enable_io()
            .build()
            .expect("launch of single-threaded tokio runtime")
    };
}

#[cfg(all(not(feature = "async-io"), feature = "tokio"))]
pub(crate) fn block_on<F: std::future::Future>(future: F) -> F::Output {
    TOKIO_RT.block_on(future)
}

#[cfg(feature = "async-io")]
pub(crate) async fn run_in_thread<F, T>(f: F) -> T
where
    F: FnOnce() -> T,
    F: Send + 'static,
    T: Send + 'static,
{
    let (s, r) = async_channel::bounded(1);

    std::thread::spawn(move || {
        let res = f();

        s.try_send(res).expect("Failed to send result");
    });

    r.recv().await.expect("Failed to receive result")
}
