# handler.rs.html -- source
Source to the Rust file `src/handler.rs`.
Keywords: rust, rustlang, rust-lang

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    use std::marker::PhantomData;
    use std::ops::Deref;

    use futures::future::{err, ok, Future};
    use futures::{Async, Poll};

    use error::Error;
    use http::StatusCode;
    use httprequest::HttpRequest;
    use httpresponse::HttpResponse;
    use resource::DefaultResource;

    /// Trait defines object that could be registered as route handler
    #[allow(unused_variables)]
    pub trait Handler<S>: 'static {
        /// The type of value that handler will return.
        type Result: Responder;

        /// Handle request
        fn handle(&self, req: &HttpRequest<S>) -> Self::Result;
    }

    /// Trait implemented by types that generate responses for clients.
    ///
    /// Types that implement this trait can be used as the return type of a handler.
    pub trait Responder {
        /// The associated item which can be returned.
        type Item: Into<AsyncResult<HttpResponse>>;

        /// The associated error which can be returned.
        type Error: Into<Error>;

        /// Convert itself to `AsyncResult` or `Error`.
        fn respond_to<S: 'static>(
            self, req: &HttpRequest<S>,
        ) -> Result<Self::Item, Self::Error>;
    }

    /// Trait implemented by types that can be extracted from request.
    ///
    /// Types that implement this trait can be used with `Route::with()` method.
    pub trait FromRequest<S>: Sized {
        /// Configuration for conversion process
        type Config: Default;

        /// Future that resolves to a Self
        type Result: Into<AsyncResult<Self>>;

        /// Convert request to a Self
        fn from_request(req: &HttpRequest<S>, cfg: &Self::Config) -> Self::Result;

        /// Convert request to a Self
        ///
        /// This method uses default extractor configuration
        fn extract(req: &HttpRequest<S>) -> Self::Result {
            Self::from_request(req, &Self::Config::default())
        }
    }

    /// Combines two different responder types into a single type
    ///
    /// ```rust
    /// # extern crate actix_web;
    /// # extern crate futures;
    /// # use futures::future::Future;
    /// use actix_web::{AsyncResponder, Either, Error, HttpRequest, HttpResponse};
    /// use futures::future::result;
    ///
    /// type RegisterResult =
    ///     Either<HttpResponse, Box<Future<Item = HttpResponse, Error = Error>>>;
    ///
    /// fn index(req: HttpRequest) -> RegisterResult {
    ///     if is_a_variant() {
    ///         // <- choose variant A
    ///         Either::A(HttpResponse::BadRequest().body("Bad data"))
    ///     } else {
    ///         Either::B(
    ///             // <- variant B
    ///             result(Ok(HttpResponse::Ok()
    ///                 .content_type("text/html")
    ///                 .body("Hello!")))
    ///                 .responder(),
    ///         )
    ///     }
    /// }
    /// # fn is_a_variant() -> bool { true }
    /// # fn main() {}
    /// ```
    #[derive(Debug)]
    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 Item = AsyncResult<HttpResponse>;
        type Error = Error;

        fn respond_to<S: 'static>(
            self, req: &HttpRequest<S>,
        ) -> Result<AsyncResult<HttpResponse>, Error> {
            match self {
                Either::A(a) => match a.respond_to(req) {
                    Ok(val) => Ok(val.into()),
                    Err(err) => Err(err.into()),
                },
                Either::B(b) => match b.respond_to(req) {
                    Ok(val) => Ok(val.into()),
                    Err(err) => Err(err.into()),
                },
            }
        }
    }

    impl<A, B, I, E> Future for Either<A, B>
    where
        A: Future<Item = I, Error = E>,
        B: Future<Item = I, Error = E>,
    {
        type Item = I;
        type Error = E;

        fn poll(&mut self) -> Poll<I, E> {
            match *self {
                Either::A(ref mut fut) => fut.poll(),
                Either::B(ref mut fut) => fut.poll(),
            }
        }
    }

    impl<T> Responder for Option<T>
    where
        T: Responder,
    {
        type Item = AsyncResult<HttpResponse>;
        type Error = Error;

        fn respond_to<S: 'static>(
            self, req: &HttpRequest<S>,
        ) -> Result<AsyncResult<HttpResponse>, Error> {
            match self {
                Some(t) => match t.respond_to(req) {
                    Ok(val) => Ok(val.into()),
                    Err(err) => Err(err.into()),
                },
                None => Ok(req.build_response(StatusCode::NOT_FOUND).finish().into()),
            }
        }
    }

    /// Convenience trait that converts `Future` object to a `Boxed` future
    ///
    /// For example loading json from request's body is async operation.
    ///
    /// ```rust
    /// # extern crate actix_web;
    /// # extern crate futures;
    /// # #[macro_use] extern crate serde_derive;
    /// use actix_web::{
    ///     App, AsyncResponder, Error, HttpMessage, HttpRequest, HttpResponse,
    /// };
    /// use futures::future::Future;
    ///
    /// #[derive(Deserialize, Debug)]
    /// struct MyObj {
    ///     name: String,
    /// }
    ///
    /// fn index(mut req: HttpRequest) -> Box<Future<Item = HttpResponse, Error = Error>> {
    ///     req.json()                   // <- get JsonBody future
    ///        .from_err()
    ///        .and_then(|val: MyObj| {  // <- deserialized value
    ///            Ok(HttpResponse::Ok().into())
    ///        })
    ///     // Construct boxed future by using `AsyncResponder::responder()` method
    ///     .responder()
    /// }
    /// # fn main() {}
    /// ```
    pub trait AsyncResponder<I, E>: Sized {
        /// Convert to a boxed future
        fn responder(self) -> Box<Future<Item = I, Error = E>>;
    }

    impl<F, I, E> AsyncResponder<I, E> for F
    where
        F: Future<Item = I, Error = E> + 'static,
        I: Responder + 'static,
        E: Into<Error> + 'static,
    {
        fn responder(self) -> Box<Future<Item = I, Error = E>> {
            Box::new(self)
        }
    }

    /// Handler<S> for Fn()
    impl<F, R, S> Handler<S> for F
    where
        F: Fn(&HttpRequest<S>) -> R + 'static,
        R: Responder + 'static,
    {
        type Result = R;

        fn handle(&self, req: &HttpRequest<S>) -> R {
            (self)(req)
        }
    }

    /// Represents async result
    ///
    /// Result could be in tree different forms.
    /// * Ok(T) - ready item
    /// * Err(E) - error happen during reply process
    /// * Future<T, E> - reply process completes in the future
    pub struct AsyncResult<I, E = Error>(Option<AsyncResultItem<I, E>>);

    impl<I, E> Future for AsyncResult<I, E> {
        type Item = I;
        type Error = E;

        fn poll(&mut self) -> Poll<I, E> {
            let res = self.0.take().expect("use after resolve");
            match res {
                AsyncResultItem::Ok(msg) => Ok(Async::Ready(msg)),
                AsyncResultItem::Err(err) => Err(err),
                AsyncResultItem::Future(mut fut) => match fut.poll() {
                    Ok(Async::NotReady) => {
                        self.0 = Some(AsyncResultItem::Future(fut));
                        Ok(Async::NotReady)
                    }
                    Ok(Async::Ready(msg)) => Ok(Async::Ready(msg)),
                    Err(err) => Err(err),
                },
            }
        }
    }

    pub(crate) enum AsyncResultItem<I, E> {
        Ok(I),
        Err(E),
        Future(Box<Future<Item = I, Error = E>>),
    }

    impl<I, E> AsyncResult<I, E> {
        /// Create async response
        #[inline]
        pub fn async(fut: Box<Future<Item = I, Error = E>>) -> AsyncResult<I, E> {
            AsyncResult(Some(AsyncResultItem::Future(fut)))
        }

        /// Send response
        #[inline]
        pub fn ok<R: Into<I>>(ok: R) -> AsyncResult<I, E> {
            AsyncResult(Some(AsyncResultItem::Ok(ok.into())))
        }

        /// Send error
        #[inline]
        pub fn err<R: Into<E>>(err: R) -> AsyncResult<I, E> {
            AsyncResult(Some(AsyncResultItem::Err(err.into())))
        }

        #[inline]
        pub(crate) fn into(self) -> AsyncResultItem<I, E> {
            self.0.expect("use after resolve")
        }

        #[cfg(test)]
        pub(crate) fn as_msg(&self) -> &I {
            match self.0.as_ref().unwrap() {
                &AsyncResultItem::Ok(ref resp) => resp,
                _ => panic!(),
            }
        }

        #[cfg(test)]
        pub(crate) fn as_err(&self) -> Option<&E> {
            match self.0.as_ref().unwrap() {
                &AsyncResultItem::Err(ref err) => Some(err),
                _ => None,
            }
        }
    }

    impl Responder for AsyncResult<HttpResponse> {
        type Item = AsyncResult<HttpResponse>;
        type Error = Error;

        fn respond_to<S>(
            self, _: &HttpRequest<S>,
        ) -> Result<AsyncResult<HttpResponse>, Error> {
            Ok(self)
        }
    }

    impl Responder for HttpResponse {
        type Item = AsyncResult<HttpResponse>;
        type Error = Error;

        #[inline]
        fn respond_to<S>(
            self, _: &HttpRequest<S>,
        ) -> Result<AsyncResult<HttpResponse>, Error> {
            Ok(AsyncResult(Some(AsyncResultItem::Ok(self))))
        }
    }

    impl<T> From<T> for AsyncResult<T> {
        #[inline]
        fn from(resp: T) -> AsyncResult<T> {
            AsyncResult(Some(AsyncResultItem::Ok(resp)))
        }
    }

    impl<T: Responder, E: Into<Error>> Responder for Result<T, E> {
        type Item = <T as Responder>::Item;
        type Error = Error;

        fn respond_to<S: 'static>(self, req: &HttpRequest<S>) -> Result<Self::Item, Error> {
            match self {
                Ok(val) => match val.respond_to(req) {
                    Ok(val) => Ok(val),
                    Err(err) => Err(err.into()),
                },
                Err(err) => Err(err.into()),
            }
        }
    }

    impl<T, E: Into<Error>> From<Result<AsyncResult<T>, E>> for AsyncResult<T> {
        #[inline]
        fn from(res: Result<AsyncResult<T>, E>) -> Self {
            match res {
                Ok(val) => val,
                Err(err) => AsyncResult(Some(AsyncResultItem::Err(err.into()))),
            }
        }
    }

    impl<T, E: Into<Error>> From<Result<T, E>> for AsyncResult<T> {
        #[inline]
        fn from(res: Result<T, E>) -> Self {
            match res {
                Ok(val) => AsyncResult(Some(AsyncResultItem::Ok(val))),
                Err(err) => AsyncResult(Some(AsyncResultItem::Err(err.into()))),
            }
        }
    }

    impl<T, E: Into<Error>> From<Result<Box<Future<Item = T, Error = Error>>, E>>
        for AsyncResult<T>
    {
        #[inline]
        fn from(res: Result<Box<Future<Item = T, Error = Error>>, E>) -> Self {
            match res {
                Ok(fut) => AsyncResult(Some(AsyncResultItem::Future(fut))),
                Err(err) => AsyncResult(Some(AsyncResultItem::Err(err.into()))),
            }
        }
    }

    impl<T> From<Box<Future<Item = T, Error = Error>>> for AsyncResult<T> {
        #[inline]
        fn from(fut: Box<Future<Item = T, Error = Error>>) -> AsyncResult<T> {
            AsyncResult(Some(AsyncResultItem::Future(fut)))
        }
    }

    /// Convenience type alias
    pub type FutureResponse<I, E = Error> = Box<Future<Item = I, Error = E>>;

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

        #[inline]
        fn respond_to<S: 'static>(
            self, req: &HttpRequest<S>,
        ) -> Result<AsyncResult<HttpResponse>, Error> {
            let req = req.clone();
            let fut = self
                .map_err(|e| e.into())
                .then(move |r| match r.respond_to(&req) {
                    Ok(reply) => match reply.into().into() {
                        AsyncResultItem::Ok(resp) => ok(resp),
                        _ => panic!("Nested async replies are not supported"),
                    },
                    Err(e) => err(e),
                });
            Ok(AsyncResult::async(Box::new(fut)))
        }
    }

    pub(crate) trait RouteHandler<S>: 'static {
        fn handle(&self, &HttpRequest<S>) -> AsyncResult<HttpResponse>;

        fn has_default_resource(&self) -> bool {
            false
        }

        fn default_resource(&mut self, _: DefaultResource<S>) {}

        fn finish(&mut self) {}
    }

    /// Route handler wrapper for Handler
    pub(crate) struct WrapHandler<S, H, R>
    where
        H: Handler<S, Result = R>,
        R: Responder,
        S: 'static,
    {
        h: H,
        s: PhantomData<S>,
    }

    impl<S, H, R> WrapHandler<S, H, R>
    where
        H: Handler<S, Result = R>,
        R: Responder,
        S: 'static,
    {
        pub fn new(h: H) -> Self {
            WrapHandler { h, s: PhantomData }
        }
    }

    impl<S, H, R> RouteHandler<S> for WrapHandler<S, H, R>
    where
        H: Handler<S, Result = R>,
        R: Responder + 'static,
        S: 'static,
    {
        fn handle(&self, req: &HttpRequest<S>) -> AsyncResult<HttpResponse> {
            match self.h.handle(req).respond_to(req) {
                Ok(reply) => reply.into(),
                Err(err) => AsyncResult::err(err.into()),
            }
        }
    }

    /// Async route handler
    pub(crate) struct AsyncHandler<S, H, F, R, E>
    where
        H: Fn(&HttpRequest<S>) -> F + 'static,
        F: Future<Item = R, Error = E> + 'static,
        R: Responder + 'static,
        E: Into<Error> + 'static,
        S: 'static,
    {
        h: Box<H>,
        s: PhantomData<S>,
    }

    impl<S, H, F, R, E> AsyncHandler<S, H, F, R, E>
    where
        H: Fn(&HttpRequest<S>) -> F + 'static,
        F: Future<Item = R, Error = E> + 'static,
        R: Responder + 'static,
        E: Into<Error> + 'static,
        S: 'static,
    {
        pub fn new(h: H) -> Self {
            AsyncHandler {
                h: Box::new(h),
                s: PhantomData,
            }
        }
    }

    impl<S, H, F, R, E> RouteHandler<S> for AsyncHandler<S, H, F, R, E>
    where
        H: Fn(&HttpRequest<S>) -> F + 'static,
        F: Future<Item = R, Error = E> + 'static,
        R: Responder + 'static,
        E: Into<Error> + 'static,
        S: 'static,
    {
        fn handle(&self, req: &HttpRequest<S>) -> AsyncResult<HttpResponse> {
            let req = req.clone();
            let fut = (self.h)(&req).map_err(|e| e.into()).then(move |r| {
                match r.respond_to(&req) {
                    Ok(reply) => match reply.into().into() {
                        AsyncResultItem::Ok(resp) => Either::A(ok(resp)),
                        AsyncResultItem::Err(e) => Either::A(err(e)),
                        AsyncResultItem::Future(fut) => Either::B(fut),
                    },
                    Err(e) => Either::A(err(e)),
                }
            });
            AsyncResult::async(Box::new(fut))
        }
    }

    /// Access an application state
    ///
    /// `S` - application state type
    ///
    /// ## Example
    ///
    /// ```rust
    /// # extern crate bytes;
    /// # extern crate actix_web;
    /// # extern crate futures;
    /// #[macro_use] extern crate serde_derive;
    /// use actix_web::{http, App, Path, State};
    ///
    /// /// Application state
    /// struct MyApp {
    ///     msg: &'static str,
    /// }
    ///
    /// #[derive(Deserialize)]
    /// struct Info {
    ///     username: String,
    /// }
    ///
    /// /// extract path info using serde
    /// fn index(data: (State<MyApp>, Path<Info>)) -> String {
    ///     let (state, path) = data;
    ///     format!("{} {}!", state.msg, path.username)
    /// }
    ///
    /// fn main() {
    ///     let app = App::with_state(MyApp { msg: "Welcome" }).resource(
    ///         "/{username}/index.html", // <- define path parameters
    ///         |r| r.method(http::Method::GET).with(index),
    ///     ); // <- use `with` extractor
    /// }
    /// ```
    pub struct State<S>(HttpRequest<S>);

    impl<S> Deref for State<S> {
        type Target = S;

        fn deref(&self) -> &S {
            self.0.state()
        }
    }

    impl<S> FromRequest<S> for State<S> {
        type Config = ();
        type Result = State<S>;

        #[inline]
        fn from_request(req: &HttpRequest<S>, _: &Self::Config) -> Self::Result {
            State(req.clone())
        }
    }

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