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/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

use super::{HttpMarker, ModelMarker, Plugin};
use std::fmt::Debug;

/// A wrapper struct which composes an `Inner` and an `Outer` [`Plugin`].
///
/// The `Inner::map` is run _then_ the `Outer::map`.
///
/// Note that the primary tool for composing HTTP plugins is
/// [`HttpPlugins`](crate::plugin::HttpPlugins), and the primary tool for composing HTTP plugins is
/// [`ModelPlugins`](crate::plugin::ModelPlugins); if you are an application writer, you should
/// prefer composing plugins using these.
#[derive(Debug)]
pub struct PluginStack<Inner, Outer> {
    inner: Inner,
    outer: Outer,
}

impl<Inner, Outer> PluginStack<Inner, Outer> {
    /// Creates a new [`PluginStack`].
    pub fn new(inner: Inner, outer: Outer) -> Self {
        PluginStack { inner, outer }
    }
}

impl<Ser, Op, T, Inner, Outer> Plugin<Ser, Op, T> for PluginStack<Inner, Outer>
where
    Inner: Plugin<Ser, Op, T>,
    Outer: Plugin<Ser, Op, Inner::Output>,
{
    type Output = Outer::Output;

    fn apply(&self, input: T) -> Self::Output {
        let svc = self.inner.apply(input);
        self.outer.apply(svc)
    }
}

impl<Inner, Outer> HttpMarker for PluginStack<Inner, Outer>
where
    Inner: HttpMarker,
    Outer: HttpMarker,
{
}

impl<Inner, Outer> ModelMarker for PluginStack<Inner, Outer>
where
    Inner: ModelMarker,
    Outer: ModelMarker,
{
}