Implement actix-web FromRequest and Responder

Fixes #130

I'm not entirely sure why this works, but the compiler seems to like
it! :D

The example is intentionally as simple as it gets, but a "real" app
should probably return Result<Event, Error> from its handlers.

Signed-off-by: Jim Crossley <jim@crossleys.org>

example-projects/actix-web-example/src/main.rs

@@ -1,31 +1,25 @@
-use actix_web::{get, post, web, App, HttpRequest, HttpResponse, HttpServer};
-use cloudevents::actix::{HttpRequestExt, HttpResponseBuilderExt};
-use cloudevents::{EventBuilder, EventBuilderV10};
+use actix_web::{get, post, App, HttpServer};
+use cloudevents::{Event, EventBuilder, EventBuilderV10};
 use serde_json::json;
 
 #[post("/")]
-async fn post_event(req: HttpRequest, payload: web::Payload) -> Result<String, actix_web::Error> {
-    let event = req.to_event(payload).await?;
+async fn post_event(event: Event) -> Event {
     println!("Received Event: {:?}", event);
-    Ok(format!("{:?}", event))
+    event
 }
 
 #[get("/")]
-async fn get_event() -> Result<HttpResponse, actix_web::Error> {
+async fn get_event() -> Event {
     let payload = json!({"hello": "world"});
 
-    Ok(HttpResponse::Ok()
-        .event(
-            EventBuilderV10::new()
-                .id("0001")
-                .ty("example.test")
-                .source("http://localhost/")
-                .data("application/json", payload)
-                .extension("someint", "10")
-                .build()
-                .unwrap(),
-        )
-        .await?)
+    EventBuilderV10::new()
+        .id("0001")
+        .ty("example.test")
+        .source("http://localhost/")
+        .data("application/json", payload)
+        .extension("someint", "10")
+        .build()
+        .unwrap()
 }
 
 #[actix_web::main]

src/actix/server_request.rs

@@ -9,7 +9,8 @@ use actix_web::http::HeaderName;
 use actix_web::web::{Bytes, BytesMut};
 use actix_web::{web, HttpMessage, HttpRequest};
 use async_trait::async_trait;
-use futures::StreamExt;
+use futures::future::LocalBoxFuture;
+use futures::{FutureExt, StreamExt};
 use std::convert::TryFrom;
 
 /// Wrapper for [`HttpRequest`] that implements [`MessageDeserializer`] trait.
@@ -112,6 +113,19 @@ pub async fn request_to_event(
         .map_err(actix_web::error::ErrorBadRequest)
 }
 
+/// So that an actix-web handler may take an Event parameter
+impl actix_web::FromRequest for Event {
+    type Config = ();
+    type Error = actix_web::Error;
+    type Future = LocalBoxFuture<'static, std::result::Result<Self, Self::Error>>;
+
+    fn from_request(r: &HttpRequest, p: &mut actix_web::dev::Payload) -> Self::Future {
+        let payload = web::Payload(p.take());
+        let request = r.to_owned();
+        async move { request_to_event(&request, payload).await }.boxed_local()
+    }
+}
+
 /// Extention Trait for [`HttpRequest`] which acts as a wrapper for the function [`request_to_event()`].
 ///
 /// This trait is sealed and cannot be implemented for types outside of this crate.

src/actix/server_response.rs

@@ -5,9 +5,11 @@ use crate::message::{
 };
 use crate::Event;
 use actix_web::dev::HttpResponseBuilder;
-use actix_web::http::{HeaderName, HeaderValue};
+use actix_web::http::{HeaderName, HeaderValue, StatusCode};
 use actix_web::HttpResponse;
 use async_trait::async_trait;
+use futures::future::LocalBoxFuture;
+use futures::FutureExt;
 use std::str::FromStr;
 
 /// Wrapper for [`HttpResponseBuilder`] that implements [`StructuredSerializer`] and [`BinarySerializer`].
@@ -76,6 +78,16 @@ pub async fn event_to_response(
         .map_err(actix_web::error::ErrorBadRequest)
 }
 
+/// So that an actix-web handler may return an Event
+impl actix_web::Responder for Event {
+    type Error = actix_web::Error;
+    type Future = LocalBoxFuture<'static, std::result::Result<HttpResponse, Self::Error>>;
+
+    fn respond_to(self, _: &actix_web::HttpRequest) -> Self::Future {
+        async { HttpResponse::build(StatusCode::OK).event(self).await }.boxed_local()
+    }
+}
+
 /// Extension Trait for [`HttpResponseBuilder`] which acts as a wrapper for the function [`event_to_response()`].
 ///
 /// This trait is sealed and cannot be implemented for types outside of this crate.