1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

use futures_core::TryFuture;
use futures_util::{future, TryFutureExt};
use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use tower_layer::Layer;
use tower_service::Service;

/// Service returned by the [`and_then`] combinator.
///
/// [`and_then`]: crate::util::ServiceExt::and_then
#[derive(Clone)]
pub struct AndThen<S, F> {
    inner: S,
    f: F,
}

impl<S, F> fmt::Debug for AndThen<S, F>
where
    S: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("AndThen")
            .field("inner", &self.inner)
            .field("f", &format_args!("{}", std::any::type_name::<F>()))
            .finish()
    }
}

pin_project_lite::pin_project! {
    /// Response future from [`AndThen`] services.
    ///
    /// [`AndThen`]: crate::util::AndThen
    pub struct AndThenFuture<F1, F2: TryFuture, N> {
        #[pin]
        inner: future::AndThen<future::ErrInto<F1, F2::Error>, F2, N>,
    }
}

impl<F1, F2: TryFuture, N> AndThenFuture<F1, F2, N> {
    pub(crate) fn new(inner: future::AndThen<future::ErrInto<F1, F2::Error>, F2, N>) -> Self {
        Self { inner }
    }
}

impl<F1, F2: TryFuture, N> std::fmt::Debug for AndThenFuture<F1, F2, N> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_tuple("AndThenFuture")
            .field(&format_args!("..."))
            .finish()
    }
}

impl<F1, F2: TryFuture, N> Future for AndThenFuture<F1, F2, N>
where
    future::AndThen<future::ErrInto<F1, F2::Error>, F2, N>: Future,
{
    type Output = <future::AndThen<future::ErrInto<F1, F2::Error>, F2, N> as Future>::Output;

    #[inline]
    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        self.project().inner.poll(cx)
    }
}

/// A [`Layer`] that produces a [`AndThen`] service.
///
/// [`Layer`]: tower_layer::Layer
#[derive(Clone, Debug)]
pub struct AndThenLayer<F> {
    f: F,
}

impl<S, F> AndThen<S, F> {
    /// Creates a new `AndThen` service.
    pub fn new(inner: S, f: F) -> Self {
        AndThen { f, inner }
    }

    /// Returns a new [`Layer`] that produces [`AndThen`] services.
    ///
    /// This is a convenience function that simply calls [`AndThenLayer::new`].
    ///
    /// [`Layer`]: tower_layer::Layer
    pub fn layer(f: F) -> AndThenLayer<F> {
        AndThenLayer { f }
    }
}

impl<S, F, Request, Fut> Service<Request> for AndThen<S, F>
where
    S: Service<Request>,
    S::Error: Into<Fut::Error>,
    F: FnOnce(S::Response) -> Fut + Clone,
    Fut: TryFuture,
{
    type Response = Fut::Ok;
    type Error = Fut::Error;
    type Future = AndThenFuture<S::Future, Fut, F>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx).map_err(Into::into)
    }

    fn call(&mut self, request: Request) -> Self::Future {
        AndThenFuture::new(self.inner.call(request).err_into().and_then(self.f.clone()))
    }
}

impl<F> AndThenLayer<F> {
    /// Creates a new [`AndThenLayer`] layer.
    pub fn new(f: F) -> Self {
        AndThenLayer { f }
    }
}

impl<S, F> Layer<S> for AndThenLayer<F>
where
    F: Clone,
{
    type Service = AndThen<S, F>;

    fn layer(&self, inner: S) -> Self::Service {
        AndThen {
            f: self.f.clone(),
            inner,
        }
    }
}