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//! Types and utilities for working with `HttpService`

mod as_service;
mod into_service;

pub use self::as_service::AsService;
pub use self::into_service::IntoService;

use futures::{Future, Poll};
use http::{Request, Response};
use http_body::Body;
use tower_service::Service;

use crate::sealed::Sealed;

/// An HTTP service
///
/// This is not intended to be implemented directly. Instead, it is a trait
/// alias of sorts. Implements the `tower_service::Service` trait using
/// `http::Request` and `http::Response` types.
pub trait HttpService<RequestBody>: Sealed<RequestBody> {
    /// Response payload.
    type ResponseBody: Body;

    /// Errors produced by the service.
    type Error;

    /// The future response value.
    type Future: Future<Item = Response<Self::ResponseBody>, Error = Self::Error>;

    /// Returns `Ready` when the service is able to process requests.
    fn poll_ready(&mut self) -> Poll<(), Self::Error>;

    /// Process the request and return the response asynchronously.
    fn call(&mut self, request: Request<RequestBody>) -> Self::Future;

    /// Wrap the HttpService so that it implements tower_service::Service
    /// directly.
    ///
    /// Since `HttpService` does not directly implement `Service`, if an
    /// `HttpService` instance needs to be used where a `T: Service` is
    /// required, it must be wrapped with a type that provides that
    /// implementation. `IntoService` does this.
    fn into_service(self) -> IntoService<Self>
    where
        Self: Sized,
    {
        IntoService::new(self)
    }

    /// Same as `into_service` but operates on an HttpService reference.
    fn as_service(&mut self) -> AsService<Self>
    where
        Self: Sized,
    {
        AsService::new(self)
    }
}

impl<T, B1, B2> HttpService<B1> for T
where
    T: Service<Request<B1>, Response = Response<B2>>,
    B2: Body,
{
    type ResponseBody = B2;
    type Error = T::Error;
    type Future = T::Future;

    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
        Service::poll_ready(self)
    }

    fn call(&mut self, request: Request<B1>) -> Self::Future {
        Service::call(self, request)
    }
}

impl<T, B1, B2> Sealed<B1> for T
where
    T: Service<Request<B1>, Response = Response<B2>>,
    B2: Body,
{
}