1use super::Layer;
2use std::fmt;
3
4/// Two middlewares chained together.
5#[derive(Clone)]
6pub struct Stack<Inner, Outer> {
7 inner: Inner,
8 outer: Outer,
9}
10
11impl<Inner, Outer> Stack<Inner, Outer> {
12 /// Create a new `Stack`.
13 pub const fn new(inner: Inner, outer: Outer) -> Self {
14 Stack { inner, outer }
15 }
16}
17
18impl<S, Inner, Outer> Layer<S> for Stack<Inner, Outer>
19where
20 Inner: Layer<S>,
21 Outer: Layer<Inner::Service>,
22{
23 type Service = Outer::Service;
24
25 fn layer(&self, service: S) -> Self::Service {
26 let inner: >::Service = self.inner.layer(inner:service);
27
28 self.outer.layer(inner)
29 }
30}
31
32impl<Inner, Outer> fmt::Debug for Stack<Inner, Outer>
33where
34 Inner: fmt::Debug,
35 Outer: fmt::Debug,
36{
37 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
38 // The generated output of nested `Stack`s is very noisy and makes
39 // it harder to understand what is in a `ServiceBuilder`.
40 //
41 // Instead, this output is designed assuming that a `Stack` is
42 // usually quite nested, and inside a `ServiceBuilder`. Therefore,
43 // this skips using `f.debug_struct()`, since each one would force
44 // a new layer of indentation.
45 //
46 // - In compact mode, a nested stack ends up just looking like a flat
47 // list of layers.
48 //
49 // - In pretty mode, while a newline is inserted between each layer,
50 // the `DebugStruct` used in the `ServiceBuilder` will inject padding
51 // to that each line is at the same indentation level.
52 //
53 // Also, the order of [outer, inner] is important, since it reflects
54 // the order that the layers were added to the stack.
55 if f.alternate() {
56 // pretty
57 write!(f, "{:#?},\n{:#?}", self.outer, self.inner)
58 } else {
59 write!(f, "{:?}, {:?}", self.outer, self.inner)
60 }
61 }
62}
63