burger 0.1.0-rc.1

An experimental service framework.
Documentation 
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

//! The [`ServiceExt::map`](crate::ServiceExt::map) combinator returns [`Map`], which extends a
//! service with a specified closure from the modifying the [`Service::Response`].
//!
//! For an asynchronous version of this combinator see [then](mod@crate::then) module.
//!
//! # Example
//!
//! ```rust
//! use burger::*;
//!
//! # #[tokio::main]
//! # async fn main() {
//! let svc = service_fn(|x: u32| async move { x.to_string() }).map(|x: String| x.parse());
//! let response: usize = svc.oneshot(32).await.unwrap();
//! assert_eq!(response, 32);
//! # }
//! ```
//!
//! # Load
//!
//! [`Load`](crate::load::Load) measurements defer to the inner service.

use std::{any, fmt};

use crate::{Middleware, Service};

/// A wrapper [`Service`] for the [`ServiceExt::map`](crate::ServiceExt::map) combinator.
///
/// See the [module](crate::map) for more information.
#[derive(Clone, Debug)]
pub struct Map<S, F> {
    inner: S,
    closure: F,
}

impl<S, F> Map<S, F> {
    pub(crate) fn new(inner: S, closure: F) -> Self {
        Self { inner, closure }
    }
}

/// The [`Service::Permit`] type for [Map].
pub struct MapPermit<'a, S, F, Request>
where
    S: Service<Request> + 'a,
{
    inner: S::Permit<'a>,
    closure: &'a F,
}

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

impl<Request, S, F, Output> Service<Request> for Map<S, F>
where
    S: Service<Request>,
    F: Fn(S::Response) -> Output,
{
    type Response = Output;
    type Permit<'a> = MapPermit<'a, S, F, Request> where S: 'a, F: 'a;

    async fn acquire(&self) -> Self::Permit<'_> {
        MapPermit {
            inner: self.inner.acquire().await,
            closure: &self.closure,
        }
    }

    async fn call(permit: Self::Permit<'_>, request: Request) -> Self::Response {
        (permit.closure)(S::call(permit.inner, request).await)
    }
}

impl<S, T, F> Middleware<S> for Map<T, F>
where
    T: Middleware<S>,
{
    type Service = Map<T::Service, F>;

    fn apply(self, svc: S) -> Self::Service {
        let Self { inner, closure } = self;
        Map {
            inner: inner.apply(svc),
            closure,
        }
    }
}