Implemented mock fountain code protocol (#45)

nomos-core/Cargo.toml

@@ -24,3 +24,4 @@ tokio = { version = "1.23", features = ["macros", "rt"] }
 [features]
 default = []
 raptor = ["raptorq"]
+mock = []

nomos-core/src/fountain/mock.rs

@@ -0,0 +1,38 @@
+// std
+// crates
+use async_trait::async_trait;
+use bytes::Bytes;
+use futures::{Stream, StreamExt};
+// internal
+use crate::fountain::{FountainCode, FountainError};
+
+/// Fountain code that does no protocol at all.
+/// Just bypasses the raw bytes into a single chunk and reconstruct from it.
+pub struct MockFountain;
+
+#[async_trait]
+impl FountainCode for MockFountain {
+    type Settings = ();
+
+    fn new(_: Self::Settings) -> Self {
+        Self
+    }
+
+    fn encode(&self, block: &[u8]) -> Box<dyn Stream<Item = Bytes> + Send + Sync + Unpin> {
+        let data = block.to_vec();
+        Box::new(futures::stream::once(Box::pin(
+            async move { Bytes::from(data) },
+        )))
+    }
+
+    async fn decode(
+        &self,
+        mut stream: impl Stream<Item = Bytes> + Send + Sync + Unpin,
+    ) -> Result<Bytes, FountainError> {
+        if let Some(chunk) = stream.next().await {
+            Ok(chunk)
+        } else {
+            Err("Stream ended before decoding was complete".into())
+        }
+    }
+}

nomos-core/src/fountain/mod.rs

@@ -1,3 +1,5 @@
+#[cfg(feature = "mock")]
+pub mod mock;
 #[cfg(feature = "raptor")]
 pub mod raptorq;