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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169

use std::{error::Error, fmt::Display, future::Future, pin::Pin};

use crate::{layer::FactoryLayer, MakeService, Service};

#[derive(Debug, Clone)]
pub enum Either<A, B> {
    Left(A),
    Right(B),
}

impl<C, F, T> FactoryLayer<C, F> for Option<T>
where
    T: FactoryLayer<C, F>,
{
    type Factory = Either<T::Factory, F>;

    #[inline]
    fn layer(&self, config: &C, inner: F) -> Self::Factory {
        match self {
            Some(fl) => Either::Left(fl.layer(config, inner)),
            None => Either::Right(inner),
        }
    }
}

impl<C, F, FLA, FLB> FactoryLayer<C, F> for Either<FLA, FLB>
where
    FLA: FactoryLayer<C, F>,
    FLB: FactoryLayer<C, F>,
{
    type Factory = Either<FLA::Factory, FLB::Factory>;

    #[inline]
    fn layer(&self, config: &C, inner: F) -> Self::Factory {
        match self {
            Either::Left(fl) => Either::Left(fl.layer(config, inner)),
            Either::Right(fl) => Either::Right(fl.layer(config, inner)),
        }
    }
}

impl<A, B> MakeService for Either<A, B>
where
    A: MakeService,
    B: MakeService,
{
    type Service = Either<A::Service, B::Service>;
    type Error = Either<A::Error, B::Error>;

    fn make_via_ref(&self, old: Option<&Self::Service>) -> Result<Self::Service, Self::Error> {
        match self {
            Either::Left(f) => match old.as_ref() {
                Some(Either::Left(left_svc)) => f.make_via_ref(Some(left_svc)),
                _ => f.make(),
            }
            .map(Either::Left)
            .map_err(Either::Left),
            Either::Right(f) => match old.as_ref() {
                Some(Either::Right(right_svc)) => f.make_via_ref(Some(right_svc)),
                _ => f.make(),
            }
            .map(Either::Right)
            .map_err(Either::Right),
        }
    }
}

impl<A, B, R> Service<R> for Either<A, B>
where
    A: Service<R>,
    B: Service<R, Response = A::Response, Error = A::Error>,
{
    type Response = A::Response;
    type Error = A::Error;
    type Future<'cx> = Either<A::Future<'cx>, B::Future<'cx>>
    where
        Self: 'cx,
        R: 'cx;

    #[inline]
    fn call(&self, req: R) -> Self::Future<'_> {
        match self {
            Either::Left(s) => Either::Left(s.call(req)),
            Either::Right(s) => Either::Right(s.call(req)),
        }
    }
}

impl<A, B> Future for Either<A, B>
where
    A: Future,
    B: Future<Output = A::Output>,
{
    type Output = A::Output;

    #[inline]
    fn poll(
        self: std::pin::Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> std::task::Poll<Self::Output> {
        match self.as_pin_mut() {
            Either::Left(fut) => fut.poll(cx),
            Either::Right(fut) => fut.poll(cx),
        }
    }
}

// Copied from futures-util.
impl<A, B> Either<A, B> {
    /// Convert `Pin<&Either<A, B>>` to `Either<Pin<&A>, Pin<&B>>`,
    /// pinned projections of the inner variants.
    #[inline]
    pub fn as_pin_ref(self: Pin<&Self>) -> Either<Pin<&A>, Pin<&B>> {
        // SAFETY: We can use `new_unchecked` because the `inner` parts are
        // guaranteed to be pinned, as they come from `self` which is pinned.
        unsafe {
            match *Pin::get_ref(self) {
                Either::Left(ref inner) => Either::Left(Pin::new_unchecked(inner)),
                Either::Right(ref inner) => Either::Right(Pin::new_unchecked(inner)),
            }
        }
    }

    /// Convert `Pin<&mut Either<A, B>>` to `Either<Pin<&mut A>, Pin<&mut B>>`,
    /// pinned projections of the inner variants.
    #[inline]
    pub fn as_pin_mut(self: Pin<&mut Self>) -> Either<Pin<&mut A>, Pin<&mut B>> {
        // SAFETY: `get_unchecked_mut` is fine because we don't move anything.
        // We can use `new_unchecked` because the `inner` parts are guaranteed
        // to be pinned, as they come from `self` which is pinned, and we never
        // offer an unpinned `&mut A` or `&mut B` through `Pin<&mut Self>`. We
        // also don't have an implementation of `Drop`, nor manual `Unpin`.
        unsafe {
            match *Pin::get_unchecked_mut(self) {
                Either::Left(ref mut inner) => Either::Left(Pin::new_unchecked(inner)),
                Either::Right(ref mut inner) => Either::Right(Pin::new_unchecked(inner)),
            }
        }
    }
}

impl<A: Display, B: Display> Display for Either<A, B> {
    #[inline]
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Either::Left(inner) => inner.fmt(f),
            Either::Right(inner) => inner.fmt(f),
        }
    }
}

impl<A: Error, B: Error> Error for Either<A, B> {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        match self {
            Either::Left(inner) => inner.source(),
            Either::Right(inner) => inner.source(),
        }
    }
}

impl<T> Either<T, T> {
    #[inline]
    pub fn into_inner(self) -> T {
        match self {
            Either::Left(t) => t,
            Either::Right(t) => t,
        }
    }
}