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#![forbid(unsafe_code)]
#![deny(
    missing_copy_implementations,
    missing_crate_level_docs,
    missing_debug_implementations,
    missing_docs,
    nonstandard_style,
    unused_qualifications
)]

//! This crate provides a common interface for server-side tls
//! acceptors, abstracting over various implementations

pub use async_trait::async_trait;
pub use futures_io::{AsyncRead, AsyncWrite};
use std::convert::Infallible;

/// This trait provides a common interface for server-side tls
/// acceptors, abstracting over various implementations.
///
/// The only implementation provided by this crate is `()`, which is
/// a noop acceptor, and passes through the `Input` type.
///
/// Implementing this trait looks like:
/// ```rust,ignore
/// #[async_trait]
/// impl<Input> Acceptor<Input> for my_tls_impl::Acceptor
/// where
///     Input: AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static,
/// {
///     type Output = my_tls_impl::TlsStream<Input>;
///     type Error = my_tls_impl::Error;
///     async fn accept(&self, input: Input) -> Result<Self::Output, Self::Error> {
///         self.accept(input).await
///     }
/// }
/// ```
#[async_trait]
pub trait Acceptor<Input>: Clone + Send + Sync + 'static
where
    Input: AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static,
{
    /// The stream type. For example, `TlsStream<Input>`
    type Output: AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static;

    /// An error type that [`Acceptor::accept`] may return
    type Error: std::fmt::Debug + Send + Sync;

    /// Transform an Input (`AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static`) into Self::Output
    ///
    /// Async trait signature:
    /// ```rust,ignore
    /// async fn accept(&self, input: Input) -> Result<Self::Output, Self::Error>;
    /// ```
    async fn accept(&self, input: Input) -> Result<Self::Output, Self::Error>;
}

#[async_trait]
impl<Input> Acceptor<Input> for ()
where
    Input: AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static,
{
    type Output = Input;
    type Error = Infallible;
    async fn accept(&self, input: Input) -> Result<Self::Output, Self::Error> {
        Ok(input)
    }
}