layered 0.3.2

Build composable async services with layered middleware.
Documentation 
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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

use std::fmt::Debug;
use std::sync::Arc;

use crate::Service;
use crate::service::DynService;

/// Extension trait for converting services to [`DynamicService`].
///
/// Provides type erasure for services, useful when working with complex service
/// compositions or storing services of different types.
pub trait DynamicServiceExt<In, Out>: Sized {
    /// Converts this service into a type-erased [`DynamicService`].
    fn into_dynamic(self) -> DynamicService<In, Out>;
}

impl<In: Send + 'static, Out: Send + 'static, T> DynamicServiceExt<In, Out> for T
where
    T: Service<In, Out = Out> + 'static,
{
    fn into_dynamic(self) -> DynamicService<In, Out> {
        DynamicService::new(self)
    }
}

/// Type-erased wrapper for [`Service`] that hides the concrete type.
///
/// Use `DynamicService` when working with complex service compositions where the
/// concrete type becomes unwieldy, or when storing services of different types in
/// collections.
///
/// Type erasure adds some overhead, but it's typically negligible compared to the
/// actual service work (network calls, database queries, etc.).
///
/// # Examples
///
/// ```
/// use layered::{DynamicService, DynamicServiceExt, Execute, Service};
///
/// async fn example() {
///     // Create a concrete service that doubles an integer and uses a closure.
///     let service = Execute::new(|v: i32| async move { v * 2 });
///
///     // Create a type-erased service
///     let service: DynamicService<i32, i32> = service.into_dynamic();
///
///     // Use it like any other service
///     let result = service.execute(42).await;
///     println!("Result: {}", result);
/// }
/// ```
pub struct DynamicService<In, Out>(Arc<DynService<'static, In, Out>>);

impl<In: Send + 'static, Out: Send + 'static> DynamicService<In, Out> {
    pub(crate) fn new<T>(strategy: T) -> Self
    where
        T: Service<In, Out = Out> + Send + Sync + 'static,
    {
        Self(DynService::new_arc(strategy))
    }
}

impl<In: Send, Out: Send> Service<In> for DynamicService<In, Out> {
    type Out = Out;

    async fn execute(&self, input: In) -> Self::Out {
        self.0.execute(input).await
    }
}

impl<In, Out> Debug for DynamicService<In, Out> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("DynamicService").finish()
    }
}

impl<In, Out> Clone for DynamicService<In, Out> {
    fn clone(&self) -> Self {
        Self(Arc::clone(&self.0))
    }
}

#[cfg_attr(coverage_nightly, coverage(off))]
#[cfg(test)]
mod tests {
    use std::sync::Mutex;

    use futures::executor::block_on;
    use static_assertions::assert_impl_all;

    use super::*;
    use crate::Execute;

    #[test]
    fn assert_types() {
        assert_impl_all!(DynamicService<(), ()>: Send, Sync, Clone, Debug);

        // If non-clonable types are used, ensure the DynamicService is still cloneable
        assert_impl_all!(DynamicService<Mutex<()>, Mutex<()>>: Send, Sync, Clone, Debug);
    }

    #[test]
    fn into_dynamic() {
        let dynamic_service: DynamicService<i32, i32> = Execute::new(|v| async move { v }).into_dynamic();

        assert_eq!(block_on(dynamic_service.execute(42)), 42);
    }

    #[test]
    fn clone_and_debug() {
        let svc: DynamicService<i32, i32> = Execute::new(|v| async move { v }).into_dynamic();
        let cloned = svc.clone();
        assert_eq!(block_on(cloned.execute(1)), 1);
        assert_eq!(format!("{svc:?}"), "DynamicService");
    }
}