Add nonfunctional complex example to diesel (#63)

diesel/Cargo.toml

@@ -5,6 +5,7 @@ authors = ["Nikolay Kim <fafhrd91@gmail.com>"]
 workspace = "../"
 
 [dependencies]
+bytes = "0.4"
 env_logger = "0.5"
 
 actix = "0.7"

diesel/src/main.rs

@@ -16,16 +16,20 @@ extern crate env_logger;
 extern crate futures;
 extern crate r2d2;
 extern crate uuid;
+extern crate bytes;
+// extern crate json;
 
+
+use bytes::BytesMut;
 use actix::prelude::*;
 use actix_web::{
-    http, middleware, server, App, AsyncResponder, FutureResponse, HttpResponse, Path,
+    http, middleware, server, App, AsyncResponder, FutureResponse, HttpResponse, Path, Error, HttpRequest,
-    State,
+    State, HttpMessage, error, Json
 };
 
 use diesel::prelude::*;
 use diesel::r2d2::ConnectionManager;
-use futures::Future;
+use futures::{future, Future, Stream};
 
 mod db;
 mod models;
@@ -39,7 +43,7 @@ struct AppState {
 }
 
 /// Async request handler
-fn index(
+fn add(
     (name, state): (Path<String>, State<AppState>),
 ) -> FutureResponse<HttpResponse> {
     // send async `CreateUser` message to a `DbExecutor`
@@ -56,6 +60,73 @@ fn index(
         .responder()
 }
 
+#[derive(Debug, Serialize, Deserialize)]
+struct MyUser {
+    name: String
+}
+
+const MAX_SIZE: usize = 262_144; // max payload size is 256k
+
+/// This handler manually load request payload and parse json object
+fn index_add((req, state): (HttpRequest<AppState>, State<AppState>)) -> impl Future<Item = HttpResponse, Error = Error> {
+    // HttpRequest::payload() is stream of Bytes objects
+    req.payload()
+        // `Future::from_err` acts like `?` in that it coerces the error type from
+        // the future into the final error type
+        .from_err()
+
+        // `fold` will asynchronously read each chunk of the request body and
+        // call supplied closure, then it resolves to result of closure
+        .fold(BytesMut::new(), move |mut body, chunk| {
+            // limit max size of in-memory payload
+            if (body.len() + chunk.len()) > MAX_SIZE {
+                Err(error::ErrorBadRequest("overflow"))
+            } else {
+                body.extend_from_slice(&chunk);
+                Ok(body)
+            }
+        })
+        // `Future::and_then` can be used to merge an asynchronous workflow with a
+        // synchronous workflow
+        //
+        // Douman NOTE:
+        // The return value in this closure helps, to clarify result for compiler
+        // as otheriwse it cannot understand it
+        .and_then(move |body| -> Box<Future<Item = HttpResponse, Error = Error>> {
+            // body is loaded, now we can deserialize serde-json
+            let r_obj = serde_json::from_slice::<MyUser>(&body);
+
+            // Send to the db for create
+            match r_obj {
+                Ok(obj) => {
+                let res = state.db.send(CreateUser { name: obj.name, })
+                               .from_err()
+                               .and_then(|res| match res {
+                                   Ok(user) => Ok(HttpResponse::Ok().json(user)),
+                                   Err(_) => Ok(HttpResponse::InternalServerError().into()),
+                               });
+
+                Box::new(res)
+                }
+                Err(_) => Box::new(future::err(error::ErrorBadRequest("Json Decode Failed")))
+            }
+        })
+}
+
+fn add2((item, state): (Json<MyUser>, State<AppState>)) -> impl Future<Item = HttpResponse, Error = Error> {
+    state.db
+         .send(CreateUser {
+            // into_inner to move into the reference, then accessing name to
+            // move the name out.
+             name: item.into_inner().name,
+         })
+         .from_err()
+         .and_then(|res| match res {
+             Ok(user) => Ok(HttpResponse::Ok().json(user)),
+             Err(_) => Ok(HttpResponse::InternalServerError().into()),
+         })
+}
+
 fn main() {
     ::std::env::set_var("RUST_LOG", "actix_web=info");
     env_logger::init();
@@ -74,7 +145,21 @@ fn main() {
         App::with_state(AppState{db: addr.clone()})
             // enable logger
             .middleware(middleware::Logger::default())
-            .resource("/{name}", |r| r.method(http::Method::GET).with(index))
+            // This can be called with:
+            // curl -S --header "Content-Type: application/json" --request POST --data '{"name":"xyz"}'  http://127.0.0.1:8080/add
+            // Use of the extractors makes some post conditions simpler such
+            // as size limit protections and built in json validation.
+            .resource("/add2", |r| {
+                r.method(http::Method::POST)
+                    .with_async_config(add2, |(json_cfg, )| {
+                        json_cfg.0.limit(4096); // <- limit size of the payload
+                    })
+            })
+            //  Manual parsing would allow custom error construction, use of
+            //  other parsers *beside* json (for example CBOR, protobuf, xml), and allows
+            //  an application to standardise on a single parser implementation.
+            .resource("/add", |r| r.method(http::Method::POST).with_async(index_add))
+            .resource("/add/{name}", |r| r.method(http::Method::GET).with(add))
     }).bind("127.0.0.1:8080")
         .unwrap()
         .start();