matrix-rust-sdk

// Copyright 2022 The Matrix.org Foundation C.I.C.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use std::{error::Error, fmt, time::Duration};

use futures_core::Future;

#[cfg(target_family = "wasm")]

use futures_util::future::{Either, select};

#[cfg(target_family = "wasm")]

use gloo_timers::future::TimeoutFuture;

#[cfg(not(target_family = "wasm"))]

use tokio::time::timeout as tokio_timeout;

/// Error type notifying that a timeout has elapsed.

#[derive(Clone, Copy, Debug, PartialEq, Eq)]

pub struct ElapsedError();

impl fmt::Display for ElapsedError {

    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

        write!(f, "time waiting for future has elapsed!")

    }

}

impl Error for ElapsedError {}

/// Wait for `future` to be completed. `future` needs to return

/// a `Result`.

///

/// If the given timeout has elapsed the method will stop waiting and return

/// an error.

pub async fn timeout<F, T>(future: F, duration: Duration) -> Result<T, ElapsedError>

where

    F: Future<Output = T>,

{

    #[cfg(not(target_family = "wasm"))]

    return tokio_timeout(duration, future).await.map_err(|_| ElapsedError());

    #[cfg(target_family = "wasm")]

    {

        let timeout_future =

            TimeoutFuture::new(u32::try_from(duration.as_millis()).expect("Overlong duration"));

        match select(std::pin::pin!(future), timeout_future).await {

            Either::Left((res, _)) => Ok(res),

            Either::Right((_, _)) => Err(ElapsedError()),

        }

    }

}

#[cfg(test)]

pub(crate) mod tests {

    use std::{future, time::Duration};

    use matrix_sdk_test_macros::async_test;

    use super::timeout;

    #[cfg(target_family = "wasm")]

    wasm_bindgen_test::wasm_bindgen_test_configure!(run_in_browser);

    #[async_test]

    async fn test_without_timeout() {

        timeout(future::ready(()), Duration::from_millis(100))

            .await

            .expect("future should have completed without ElapsedError");

    }

    #[async_test]

    async fn test_with_timeout() {

        timeout(future::pending::<()>(), Duration::from_millis(100))

            .await

            .expect_err("future should return an ElapsedError");

    }

}