//! An extension trait for Futures that provides a variety of convenient adapters.

mod with_cancellation_token;

use with_cancellation_token::{WithCancellationTokenFuture, WithCancellationTokenFutureOwned};

use std::future::Future;

use crate::sync::CancellationToken;

/// A trait which contains a variety of convenient adapters and utilities for `Future`s.

pub trait FutureExt: Future {

    cfg_time! {

        /// A wrapper around [`tokio::time::timeout`], with the advantage that it is easier to write

        /// fluent call chains.

        ///

        /// # Examples

        ///

        /// ```rust

        /// use tokio::{sync::oneshot, time::Duration};

        /// use tokio_util::future::FutureExt;

        ///

        /// # async fn dox() {

        /// let (_tx, rx) = oneshot::channel::<()>();

        ///

        /// let res = rx.timeout(Duration::from_millis(10)).await;

        /// assert!(res.is_err());

        /// # }

        /// ```

        fn timeout(self, timeout: std::time::Duration) -> tokio::time::Timeout<Self>

        where

            Self: Sized,

        {

            tokio::time::timeout(timeout, self)

        }

        /// A wrapper around [`tokio::time::timeout_at`], with the advantage that it is easier to write

        /// fluent call chains.

        ///

        /// # Examples

        ///

        /// ```rust

        /// use tokio::{sync::oneshot, time::{Duration, Instant}};

        /// use tokio_util::future::FutureExt;

        ///

        /// # async fn dox() {

        /// let (_tx, rx) = oneshot::channel::<()>();

        /// let deadline = Instant::now() + Duration::from_millis(10);

        ///

        /// let res = rx.timeout_at(deadline).await;

        /// assert!(res.is_err());

        /// # }

        /// ```

        fn timeout_at(self, deadline: tokio::time::Instant) -> tokio::time::Timeout<Self>

        where

            Self: Sized,

        {

            tokio::time::timeout_at(deadline, self)

        }

    }

    /// Similar to [`CancellationToken::run_until_cancelled`],

    /// but with the advantage that it is easier to write fluent call chains,

    /// and biased towards waiting for [`CancellationToken`] to complete.

    ///

    /// # Fairness

    ///

    /// Calling this on an already-cancelled token directly returns `None`.

    /// For all subsequent polls, in case of concurrent completion and

    /// cancellation, this is biased towards the future completion.

    ///

    /// # Examples

    ///

    /// ```rust

    /// use tokio::sync::oneshot;

    /// use tokio_util::future::FutureExt;

    /// use tokio_util::sync::CancellationToken;

    ///

    /// # async fn dox() {

    /// let (_tx, rx) = oneshot::channel::<()>();

    /// let token = CancellationToken::new();

    /// let token_clone = token.clone();

    /// tokio::spawn(async move {

    ///     tokio::time::sleep(std::time::Duration::from_millis(10)).await;

    ///     token.cancel();

    /// });

    /// assert!(rx.with_cancellation_token(&token_clone).await.is_none())

    /// # }

    /// ```

    fn with_cancellation_token(

        self,

        cancellation_token: &CancellationToken,

    ) -> WithCancellationTokenFuture<'_, Self>

    where

        Self: Sized,

    {

        WithCancellationTokenFuture::new(cancellation_token, self)

    }

    /// Similar to [`CancellationToken::run_until_cancelled_owned`],

    /// but with the advantage that it is easier to write fluent call chains,

    /// and biased towards waiting for [`CancellationToken`] to complete.

    ///

    /// # Fairness

    ///

    /// Calling this on an already-cancelled token directly returns `None`.

    /// For all subsequent polls, in case of concurrent completion and

    /// cancellation, this is biased towards the future completion.

    ///

    /// # Examples

    ///

    /// ```rust

    /// use tokio::sync::oneshot;

    /// use tokio_util::future::FutureExt;

    /// use tokio_util::sync::CancellationToken;

    ///

    /// # async fn dox() {

    /// let (_tx, rx) = oneshot::channel::<()>();

    /// let token = CancellationToken::new();

    /// let token_clone = token.clone();

    /// tokio::spawn(async move {

    ///     tokio::time::sleep(std::time::Duration::from_millis(10)).await;

    ///     token.cancel();

    /// });

    /// assert!(rx.with_cancellation_token_owned(token_clone).await.is_none())

    /// # }

    /// ```

    fn with_cancellation_token_owned(

        self,

        cancellation_token: CancellationToken,

    ) -> WithCancellationTokenFutureOwned<Self>

    where

        Self: Sized,

    {

        WithCancellationTokenFutureOwned::new(cancellation_token, self)

    }

}

impl<T: Future + ?Sized> FutureExt for T {}