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// Copyright 2018 MaidSafe.net limited.
//
// This SAFE Network Software is licensed to you under The General Public License (GPL), version 3.
// Unless required by applicable law or agreed to in writing, the SAFE Network Software distributed
// under the GPL Licence is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. Please review the Licences for the specific language governing
// permissions and limitations relating to use of the SAFE Network Software.

use futures::Future;

/// This is the equivalent `try!` adapted to deal with futures. It is to be
/// read as `future-try`.  This will convert errors from `Result` into a `done`
/// future with corresponding error and return.
#[macro_export]
macro_rules! fry {
    ($res:expr) => {
        match $res {
            Ok(elt) => elt,
            Err(e) => {
                use $crate::utils::FutureExt;
                return ::futures::future::err(From::from(e)).into_box();
            }
        }
    };
}

/// This is the equivalent of `Result::Ok()` adapted to deal with futures. This
/// should be used to construct the return type equivalent of `Result::Ok` in
/// futures paradigm.
#[macro_export]
macro_rules! ok {
    ($elt:expr) => {{
        use $crate::utils::FutureExt;
        ::futures::future::ok($elt).into_box()
    }};
}

/// This is the equivalent of `Result::Ok()` adapted to deal with futures. This
/// should be used to construct the return type equivalent of `Result::Err` in
/// futures paradigm.
#[macro_export]
macro_rules! err {
    ($elt:expr) => {{
        use $crate::utils::FutureExt;
        ::futures::future::err(From::from($elt)).into_box()
    }};
}

/// Additional future combinators.
pub trait FutureExt: Future + Sized {
    /// Box this future. Similar to `boxed` combinator, but does not require
    /// the future to implement `Send`.
    fn into_box(self) -> Box<dyn Future<Item = Self::Item, Error = Self::Error>>;
}

impl<F: Future + 'static> FutureExt for F {
    // TODO: when trait/impl specialization lands, try to implement this so that
    // it's a no-op when called on already boxed futures.
    fn into_box(self) -> Box<dyn Future<Item = Self::Item, Error = Self::Error>> {
        Box::new(self)
    }
}