actix-web/src/responder.rs

use actix_http::{dev::ResponseBuilder, http::StatusCode, Error, Response};
use bytes::{Bytes, BytesMut};
use futures::future::{err, ok, Either as EitherFuture, FutureResult};
use futures::{Future, IntoFuture, Poll};

use crate::request::HttpRequest;

/// Trait implemented by types that can be converted to a http response.
///
/// Types that implement this trait can be used as the return type of a handler.
pub trait Responder {
    /// The associated error which can be returned.
    type Error: Into<Error>;

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

    /// Convert itself to `AsyncResult` or `Error`.
    fn respond_to(self, req: &HttpRequest) -> Self::Future;
}

impl Responder for Response {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    #[inline]
    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(self)
    }
}

impl<T> Responder for Option<T>
where
    T: Responder,
{
    type Error = T::Error;
    type Future = EitherFuture<
        <T::Future as IntoFuture>::Future,
        FutureResult<Response, T::Error>,
    >;

    fn respond_to(self, req: &HttpRequest) -> Self::Future {
        match self {
            Some(t) => EitherFuture::A(t.respond_to(req).into_future()),
            None => EitherFuture::B(ok(Response::build(StatusCode::NOT_FOUND).finish())),
        }
    }
}

impl<T, E> Responder for Result<T, E>
where
    T: Responder,
    E: Into<Error>,
{
    type Error = Error;
    type Future = EitherFuture<
        ResponseFuture<<T::Future as IntoFuture>::Future>,
        FutureResult<Response, Error>,
    >;

    fn respond_to(self, req: &HttpRequest) -> Self::Future {
        match self {
            Ok(val) => {
                EitherFuture::A(ResponseFuture::new(val.respond_to(req).into_future()))
            }
            Err(e) => EitherFuture::B(err(e.into())),
        }
    }
}

impl Responder for ResponseBuilder {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    #[inline]
    fn respond_to(mut self, _: &HttpRequest) -> Self::Future {
        ok(self.finish())
    }
}

impl Responder for () {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK).finish())
    }
}

impl Responder for &'static str {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("text/plain; charset=utf-8")
            .body(self))
    }
}

impl Responder for &'static [u8] {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("application/octet-stream")
            .body(self))
    }
}

impl Responder for String {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("text/plain; charset=utf-8")
            .body(self))
    }
}

impl<'a> Responder for &'a String {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("text/plain; charset=utf-8")
            .body(self))
    }
}

impl Responder for Bytes {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("application/octet-stream")
            .body(self))
    }
}

impl Responder for BytesMut {
    type Error = Error;
    type Future = FutureResult<Response, Error>;

    fn respond_to(self, _: &HttpRequest) -> Self::Future {
        ok(Response::build(StatusCode::OK)
            .content_type("application/octet-stream")
            .body(self))
    }
}

/// Combines two different responder types into a single type
///
/// ```rust
/// # use futures::future::{ok, Future};
/// use actix_web::{Either, Error, HttpResponse};
///
/// type RegisterResult =
///     Either<HttpResponse, Box<Future<Item = HttpResponse, Error = Error>>>;
///
/// fn index() -> RegisterResult {
///     if is_a_variant() {
///         // <- choose left variant
///         Either::A(HttpResponse::BadRequest().body("Bad data"))
///     } else {
///         Either::B(
///             // <- Right variant
///             Box::new(ok(HttpResponse::Ok()
///                 .content_type("text/html")
///                 .body("Hello!")))
///         )
///     }
/// }
/// # fn is_a_variant() -> bool { true }
/// # fn main() {}
/// ```
#[derive(Debug, PartialEq)]
pub enum Either<A, B> {
    /// First branch of the type
    A(A),
    /// Second branch of the type
    B(B),
}

impl<A, B> Responder for Either<A, B>
where
    A: Responder,
    B: Responder,
{
    type Error = Error;
    type Future = EitherResponder<
        <A::Future as IntoFuture>::Future,
        <B::Future as IntoFuture>::Future,
    >;

    fn respond_to(self, req: &HttpRequest) -> Self::Future {
        match self {
            Either::A(a) => EitherResponder::A(a.respond_to(req).into_future()),
            Either::B(b) => EitherResponder::B(b.respond_to(req).into_future()),
        }
    }
}

pub enum EitherResponder<A, B>
where
    A: Future<Item = Response>,
    A::Error: Into<Error>,
    B: Future<Item = Response>,
    B::Error: Into<Error>,
{
    A(A),
    B(B),
}

impl<A, B> Future for EitherResponder<A, B>
where
    A: Future<Item = Response>,
    A::Error: Into<Error>,
    B: Future<Item = Response>,
    B::Error: Into<Error>,
{
    type Item = Response;
    type Error = Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        match self {
            EitherResponder::A(ref mut fut) => Ok(fut.poll().map_err(|e| e.into())?),
            EitherResponder::B(ref mut fut) => Ok(fut.poll().map_err(|e| e.into())?),
        }
    }
}

impl<I, E> Responder for Box<Future<Item = I, Error = E>>
where
    I: Responder + 'static,
    E: Into<Error> + 'static,
{
    type Error = Error;
    type Future = Box<Future<Item = Response, Error = Error>>;

    #[inline]
    fn respond_to(self, req: &HttpRequest) -> Self::Future {
        let req = req.clone();
        Box::new(
            self.map_err(|e| e.into())
                .and_then(move |r| ResponseFuture(r.respond_to(&req).into_future())),
        )
    }
}

pub struct ResponseFuture<T>(T);

impl<T> ResponseFuture<T> {
    pub fn new(fut: T) -> Self {
        ResponseFuture(fut)
    }
}

impl<T> Future for ResponseFuture<T>
where
    T: Future<Item = Response>,
    T::Error: Into<Error>,
{
    type Item = Response;
    type Error = Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        Ok(self.0.poll().map_err(|e| e.into())?)
    }
}