New feature: NATS bindings (#185)

* feat: add NATS protocol bindings

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* chore: run cargo fix & fmt

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* fix: issues with docs

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* Apply suggestions from code review

Co-authored-by: Lazzaretti <fabrizio@lazzaretti.me>

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* feat: apply suggestions from code review

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* feat: add test for v0.3 deserialization

Signed-off-by: Jakub Noga <jakub.noga@softchameleon.io>

* chore: run cargo fmt

Signed-off-by: Fabrizio Lazzaretti <fabrizio@lazzaretti.me>

Co-authored-by: Jakub Noga <jakub.noga@softchameleon.io>
Co-authored-by: Lazzaretti <fabrizio@lazzaretti.me>

.github/workflows/rust_tests.yml

@@ -146,3 +146,10 @@ jobs:
         toolchain: ${{ matrix.toolchain }}
         args: --target ${{ matrix.target }} --manifest-path ./example-projects/poem-example/Cargo.toml
 
+    - uses: actions-rs/cargo@v1
+      name: "Build nats-example"
+      if: matrix.target == 'x86_64-unknown-linux-gnu' && matrix.toolchain == 'stable'
+      with:
+        command: build
+        toolchain: ${{ matrix.toolchain }}
+        args: --target ${{ matrix.target }} --manifest-path ./example-projects/nats-example/Cargo.toml

.gitignore

@@ -1,4 +1,6 @@
 **/target
 
 .idea
+.vscode
+.DS_Store
 **/Cargo.lock

Cargo.toml

@@ -24,6 +24,7 @@ rdkafka = ["rdkafka-lib", "bytes", "futures"]
 warp = ["warp-lib", "bytes", "http", "hyper"]
 axum = ["bytes", "http", "hyper", "axum-lib", "http-body", "async-trait"]
 poem = ["bytes", "http", "poem-lib", "hyper", "async-trait"]
+nats = ["nats-lib"]
 
 [dependencies]
 serde = { version = "^1.0", features = ["derive"] }
@@ -50,6 +51,7 @@ hyper = { version = "^0.14", optional = true }
 axum-lib = { version = "^0.5", optional = true , package="axum"}
 http-body = { version = "^0.4", optional = true }
 poem-lib = { version = "=1.2.34", optional = true, package = "poem" }
+nats-lib = { version = "0.21.0", optional = true, package = "nats" }
 
 [target."cfg(not(target_arch = \"wasm32\"))".dependencies]
 hostname = "^0.3"

README.md

@@ -15,7 +15,7 @@ Note: This project is WIP under active development, hence all APIs are considere
 | JSON Event Format             | ✓ | ✓ |
 | Kafka Protocol Binding        | ✓ | ✓ |
 | MQTT Protocol Binding         | ✕ | ✕ |
-| NATS Protocol Binding         | ✕ | ✕ |
+| NATS Protocol Binding         | ✓ | ✓ |
 | Web hook                      | ✕ | ✕ |
 
 ## Crate Structure
@@ -30,6 +30,7 @@ enabled by a specific [feature flag]:
 * `warp`: Integration with [warp](https://github.com/seanmonstar/warp/).
 * `reqwest`: Integration with [reqwest](https://github.com/seanmonstar/reqwest).
 * `rdkafka`: Integration with [rdkafka](https://fede1024.github.io/rust-rdkafka).
+* `nats`: Integration with [nats](https://github.com/nats-io/nats.rs)
 
 This crate is continuously tested to work with GNU libc, WASM and musl
 toolchains.
@@ -64,6 +65,7 @@ Checkout the examples using our integrations to learn how to send and receive ev
 * [Reqwest/WASM Example](example-projects/reqwest-wasm-example)
 * [Kafka Example](example-projects/rdkafka-example)
 * [Warp Example](example-projects/warp-example)
+* [NATS Example](example-projects/nats-example)
 
 ## Development & Contributing
 

example-projects/nats-example/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "nats-example"
+version = "0.1.0"
+authors = ["Jakub Noga <jakub.noga@softchameleon.io>"]
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+cloudevents-sdk = { path = "../..", features = ["nats"] }
+serde_json = "^1.0"
+nats = "0.21.0"

example-projects/nats-example/src/main.rs

@@ -0,0 +1,47 @@
+use std::{error::Error, thread};
+
+use cloudevents::binding::nats::{MessageExt, NatsCloudEvent};
+use cloudevents::{Event, EventBuilder, EventBuilderV10};
+use serde_json::json;
+
+/// First spin up a nats server i.e.
+/// ```bash
+/// docker run -p 4222:4222 -ti nats:latest
+/// ```
+fn main() -> Result<(), Box<dyn Error>> {
+    let nc = nats::connect("localhost:4222").unwrap();
+
+    let event = EventBuilderV10::new()
+        .id("123".to_string())
+        .ty("example.test")
+        .source("http://localhost/")
+        .data("application/json", json!({"hello": "world"}))
+        .build()
+        .unwrap();
+
+    let n_msg = NatsCloudEvent::from_event(event).unwrap();
+
+    let sub = nc.subscribe("test").unwrap();
+
+    let t = thread::spawn(move || -> Result<Event, String> {
+        match sub.next() {
+            Some(msg) => match msg.to_event() {
+                Ok(evt) => Ok(evt),
+                Err(e) => Err(e.to_string()),
+            },
+            None => Err("Unsubed or disconnected".to_string()),
+        }
+    });
+
+    nc.publish("test", n_msg)?;
+
+    let maybe_event = t.join().unwrap();
+
+    if let Ok(evt) = maybe_event {
+        println!("{}", evt.to_string());
+    } else {
+        println!("{}", maybe_event.unwrap_err().to_string());
+    }
+
+    Ok(())
+}

src/binding/mod.rs

@@ -13,6 +13,8 @@ pub mod axum;
     feature = "poem"
 ))]
 pub mod http;
+#[cfg(feature = "nats")]
+pub mod nats;
 #[cfg(feature = "poem")]
 pub mod poem;
 #[cfg(feature = "rdkafka")]

src/binding/nats/deserializer.rs

@@ -0,0 +1,77 @@
+use crate::{
+    message::{Result, StructuredDeserializer},
+    Event,
+};
+
+use nats_lib as nats;
+
+impl StructuredDeserializer for nats::Message {
+    fn deserialize_structured<R: Sized, V: crate::message::StructuredSerializer<R>>(
+        self,
+        serializer: V,
+    ) -> crate::message::Result<R> {
+        serializer.set_structured_event(self.data.to_vec())
+    }
+}
+
+/// Trait implemented by [`nats::Message`] to enable convenient deserialization to [`Event`]
+///
+/// Trait sealed <https://rust-lang.github.io/api-guidelines/future-proofing.html#sealed-traits-protect-against-downstream-implementations-c-sealed>
+pub trait MessageExt: private::Sealed {
+    fn to_event(&self) -> Result<Event>;
+}
+
+impl MessageExt for nats::Message {
+    fn to_event(&self) -> Result<Event> {
+        StructuredDeserializer::into_event(self.to_owned())
+    }
+}
+
+mod private {
+    use nats_lib as nats;
+
+    // Sealing the MessageExt
+    pub trait Sealed {}
+    impl Sealed for nats::Message {}
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test::fixtures;
+    use nats_lib as nats;
+    use serde_json::json;
+
+    use super::*;
+
+    #[test]
+    fn test_structured_deserialize_v10() {
+        let expected = fixtures::v10::full_json_data_string_extension();
+
+        let nats_message = nats::Message::new(
+            "not_relevant",
+            None,
+            json!(expected.clone()).to_string().as_bytes().to_vec(),
+            None,
+        );
+
+        let actual = nats_message.to_event().unwrap();
+
+        assert_eq!(expected, actual)
+    }
+
+    #[test]
+    fn test_structured_deserialize_v03() {
+        let expected = fixtures::v03::full_json_data();
+
+        let nats_message = nats::Message::new(
+            "not_relevant",
+            None,
+            json!(expected.clone()).to_string().as_bytes().to_vec(),
+            None,
+        );
+
+        let actual = nats_message.to_event().unwrap();
+
+        assert_eq!(expected, actual)
+    }
+}

src/binding/nats/mod.rs

@@ -0,0 +1,43 @@
+//! This module provides bindings between [cloudevents-sdk](https://docs.rs/cloudevents-sdk) and [nats](https://docs.rs/nats)
+//! ## Examples
+//! Deserialize [nats::Message](https://docs.rs/nats/0.21.0/nats/struct.Message.html) into [Event](https://docs.rs/cloudevents-sdk/latest/cloudevents/event/struct.Event.html)
+//! ```
+//!     use nats_lib as nats;
+//!     use cloudevents::binding::nats::MessageExt;
+//!     
+//!     fn consume() {
+//!       let nc = nats::connect("localhost:4222").unwrap();
+//!       let sub = nc.subscribe("test").unwrap();
+//!       let nats_message = sub.next().unwrap();
+//!       let cloud_event = nats_message.to_event().unwrap();
+//!
+//!       println!("{}", cloud_event.to_string());
+//!     }
+//! ```
+//!
+//! Serialize [Event](https://docs.rs/cloudevents-sdk/latest/cloudevents/event/struct.Event.html) into [NatsCloudEvent] and publish to nats subject
+//! ```
+//!     use nats_lib as nats;
+//!     use cloudevents::binding::nats::NatsCloudEvent;
+//!     use cloudevents::{EventBuilder, EventBuilderV10, Event};
+//!     use serde_json::json;
+//!
+//!     fn publish() {
+//!       let nc = nats::connect("localhost:4222").unwrap();
+//!
+//!       let event = EventBuilderV10::new()
+//!           .id("123".to_string())
+//!           .ty("example.test")
+//!           .source("http://localhost/")
+//!           .data("application/json", json!({"hello": "world"}))
+//!           .build()
+//!           .unwrap();
+//!
+//!       nc.publish("whatever.subject.you.like", NatsCloudEvent::from_event(event).unwrap()).unwrap();
+//!     }
+//! ```
+mod deserializer;
+mod serializer;
+
+pub use deserializer::MessageExt;
+pub use serializer::NatsCloudEvent;

src/binding/nats/serializer.rs

@@ -0,0 +1,26 @@
+use crate::{
+    message::{Error, Result},
+    Event,
+};
+
+/// Helper struct containing text data bytes of JSON serialized [Event]
+///
+/// Implements [`AsRef`] so it can be directly passed to [`nats::Connection`](https://docs.rs/nats/0.21.0/nats/struct.Connection.html) methods as payload.
+pub struct NatsCloudEvent {
+    pub payload: Vec<u8>,
+}
+
+impl AsRef<[u8]> for NatsCloudEvent {
+    fn as_ref(&self) -> &[u8] {
+        &self.payload.as_ref()
+    }
+}
+
+impl NatsCloudEvent {
+    pub fn from_event(event: Event) -> Result<Self> {
+        match serde_json::to_vec(&event) {
+            Ok(payload) => Ok(Self { payload }),
+            Err(e) => Err(Error::SerdeJsonError { source: e }),
+        }
+    }
+}