decouple simulation test from mycelium

1 files changed, 31 insertions, 14 deletions

diff --git a/src/transport/sim.rs b/src/transport/sim.rs
index 2410bba..a558e9f 100644
--- a/src/transport/sim.rs
+++ b/src/transport/sim.rs
@@ -1,9 +1,9 @@
 //! A simulated network for tests: many nodes in one process, each with a
 //! [`SimTransport`] on a shared [`SimNet`].
 //!
-//! Messages go through the Mycelium wire encoding (`mycelium::encode_message`), so the
-//! codec is exercised as in production; without the mycelium feature, through the wire
-//! encoding alone, as libp2p and Tor send it. The net delays, loses and duplicates them per
+//! Messages go through the wire encoding (`WIRE`, as libp2p and Tor send it), so the
+//! codec is exercised as in production; a net can use a transport's envelope instead
+//! (`SimNet::with_codec`; Mycelium's tests run a swarm on its envelope). The net delays, loses and duplicates them per
 //! link, from a seeded generator; nodes can be taken down (everything to and from them
 //! is lost) and brought up again; and a test can inject a message as if a node had sent
 //! it, e.g. one that arrives late.
@@ -25,8 +25,6 @@ use bytes::Bytes;
 use tokio::sync::{mpsc, oneshot};
 use tracing::{debug, warn};
 
-#[cfg(feature = "mycelium")]
-pub(crate) use super::mycelium::{decode_message, encode_message};
 use super::{EncodedMessage, MessageHandler, MessageKind, ParsedMessage, Transport};
 use crate::locks::MutexExt;
 use crate::testrand::Rng;
@@ -88,11 +86,19 @@ struct NetInner {
 #[derive(Clone)]
 pub(crate) struct SimNet {
     inner: Arc<Mutex<NetInner>>,
+    codec: Codec,
 }
 
 impl SimNet {
+    /// Messages in the wire encoding alone (`WIRE`).
     pub(crate) fn new(seed: u64) -> Self {
+        Self::with_codec(seed, WIRE)
+    }
+
+    /// Messages put into bytes by `codec`.
+    pub(crate) fn with_codec(seed: u64, codec: Codec) -> Self {
         Self {
+            codec,
             inner: Arc::new(Mutex::new(NetInner {
                 rng: Rng::new(seed),
                 default_link: LinkParams::default(),
@@ -217,7 +223,7 @@ impl SimNet {
     /// net. For messages a real node wouldn't send at that moment, e.g. one sent long
     /// ago and delivered late.
     pub(crate) async fn inject(&self, from: &str, to: &str, message: &ParsedMessage) -> Result<()> {
-        let encoded = encode_message(to, message)?;
+        let encoded = (self.codec.encode)(to, message)?;
         let (handled_tx, handled_rx) = oneshot::channel();
         let delivery = Delivery {
             from: from.to_owned(),
@@ -251,9 +257,22 @@ pub(crate) struct SimTransport {
     inbox: tokio::sync::Mutex<Option<mpsc::UnboundedReceiver<Delivery>>>,
 }
 
-/// Without Mycelium: a message in the wire encoding alone, as libp2p and Tor send it.
-#[cfg(not(feature = "mycelium"))]
-pub(crate) fn encode_message(peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
+/// How a simulated net puts messages into bytes and back (`SimNet::with_codec`): the
+/// wire encoding alone (`WIRE`, as libp2p and Tor send it), or a transport's envelope
+/// around it (Mycelium's: `mycelium::CODEC`), so a whole swarm runs on that envelope.
+#[derive(Clone, Copy)]
+pub(crate) struct Codec {
+    pub(crate) encode: fn(&str, &ParsedMessage) -> Result<EncodedMessage>,
+    pub(crate) decode: fn(&[u8]) -> Result<ParsedMessage>,
+}
+
+/// The wire encoding alone (`transport::wire`).
+pub(crate) const WIRE: Codec = Codec {
+    encode: wire_encode,
+    decode: wire_decode,
+};
+
+fn wire_encode(peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
     let body = super::wire::encode(message)?;
     Ok(EncodedMessage {
         peer: peer.to_owned(),
@@ -265,9 +284,7 @@ pub(crate) fn encode_message(peer: &str, message: &ParsedMessage) -> Result<Enco
     })
 }
 
-/// The message in a body made by [`encode_message`].
-#[cfg(not(feature = "mycelium"))]
-pub(crate) fn decode_message(body: &[u8]) -> Result<ParsedMessage> {
+fn wire_decode(body: &[u8]) -> Result<ParsedMessage> {
     Ok(super::wire::decode(body)?)
 }
 
@@ -296,7 +313,7 @@ impl Transport for SimTransport {
     }
 
     fn encode(&self, peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
-        encode_message(peer, message)
+        (self.net.codec.encode)(peer, message)
     }
 
     /// Always accepted: the net loses messages silently, like Mycelium once it has
@@ -312,7 +329,7 @@ impl Transport for SimTransport {
             bail!("consumer of {} already started", self.id);
         };
         while let Some(delivery) = inbox.recv().await {
-            match decode_message(&delivery.body) {
+            match (self.net.codec.decode)(&delivery.body) {
                 Ok(message) => {
                     debug!(node = %self.id, from = %delivery.from, message = ?message, "Simulated delivery");
                     if let Err(error) = handler(delivery.from, message, delivery.payload_len).await