Make `ask` field of `Rate` private

swap/src/asb/fixed_rate.rs

@@ -13,8 +13,8 @@ impl FixedRate {
 
 impl Default for FixedRate {
     fn default() -> Self {
-        Self(Rate {
-            ask: bitcoin::Amount::from_btc(Self::RATE).expect("Static value should never fail"),
-        })
+        let ask = bitcoin::Amount::from_btc(Self::RATE).expect("Static value should never fail");
+
+        Self(Rate::new(ask))
     }
 }

swap/src/asb/rate.rs

@@ -9,7 +9,7 @@ use std::fmt::{Debug, Display, Formatter};
 /// sell 1 XMR.
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Rate {
-    pub ask: bitcoin::Amount,
+    ask: bitcoin::Amount,
 }
 
 impl Rate {
@@ -17,6 +17,14 @@ impl Rate {
         ask: bitcoin::Amount::ZERO,
     };
 
+    pub fn new(ask: bitcoin::Amount) -> Self {
+        Self { ask }
+    }
+
+    pub fn ask(&self) -> bitcoin::Amount {
+        self.ask
+    }
+
     // This function takes the quote amount as it is what Bob sends to Alice in the
     // swap request
     pub fn sell_quote(&self, quote: bitcoin::Amount) -> Result<monero::Amount> {

swap/src/kraken.rs

@@ -31,7 +31,7 @@ pub fn connect() -> Result<RateUpdateStream> {
                     let mut stream = connection::new().await?;
 
                     while let Some(update) = stream.try_next().await.map_err(to_backoff)? {
-                        let send_result = rate_update.send(Ok(update));
+                        let send_result = rate_update.send(Ok(Rate::new(update.ask)));
 
                         if send_result.is_err() {
                             return Err(backoff::Error::Permanent(anyhow!(
@@ -120,7 +120,7 @@ mod connection {
     use futures::stream::BoxStream;
     use tokio_tungstenite::tungstenite;
 
-    pub async fn new() -> Result<BoxStream<'static, Result<Rate, Error>>> {
+    pub async fn new() -> Result<BoxStream<'static, Result<wire::PriceUpdate, Error>>> {
         let (mut rate_stream, _) = tokio_tungstenite::connect_async("wss://ws.kraken.com")
             .await
             .context("Failed to connect to Kraken websocket API")?;
@@ -134,12 +134,12 @@ mod connection {
         Ok(stream)
     }
 
-    /// Parse a websocket message into a [`Rate`].
+    /// Parse a websocket message into a [`wire::PriceUpdate`].
     ///
     /// Messages which are not actually ticker updates are ignored and result in
     /// `None` being returned. In the context of a [`TryStream`], these will
     /// simply be filtered out.
-    async fn parse_message(msg: tungstenite::Message) -> Result<Option<Rate>, Error> {
+    async fn parse_message(msg: tungstenite::Message) -> Result<Option<wire::PriceUpdate>, Error> {
         let msg = match msg {
             tungstenite::Message::Text(msg) => msg,
             tungstenite::Message::Close(close_frame) => {
@@ -182,7 +182,7 @@ mod connection {
                 return Ok(None);
             }
             // if the message is not an event, it is a ticker update or an unknown event
-            Err(_) => match serde_json::from_str::<wire::TickerUpdate>(&msg) {
+            Err(_) => match serde_json::from_str::<wire::PriceUpdate>(&msg) {
                 Ok(ticker) => ticker,
                 Err(e) => {
                     tracing::warn!(%e, "Failed to deserialize message '{}' as ticker update", msg);
@@ -192,8 +192,6 @@ mod connection {
             },
         };
 
-        let update = Rate::try_from(update)?;
-
         Ok(Some(update))
     }
 
@@ -247,6 +245,13 @@ mod wire {
         BitcoinParseAmount(#[from] ParseAmountError),
     }
 
+    /// Represents an update within the price ticker.
+    #[derive(Debug, Deserialize)]
+    #[serde(try_from = "TickerUpdate")]
+    pub struct PriceUpdate {
+        pub ask: bitcoin::Amount,
+    }
+
     #[derive(Debug, Deserialize)]
     #[serde(transparent)]
     pub struct TickerUpdate(Vec<TickerField>);
@@ -273,7 +278,7 @@ mod wire {
         Number(u64),
     }
 
-    impl TryFrom<TickerUpdate> for Rate {
+    impl TryFrom<TickerUpdate> for PriceUpdate {
         type Error = Error;
 
         fn try_from(value: TickerUpdate) -> Result<Self, Error> {
@@ -293,7 +298,7 @@ mod wire {
                 _ => return Err(Error::UnexpectedAskRateElementType),
             };
 
-            Ok(Self { ask })
+            Ok(PriceUpdate { ask })
         }
     }
 

swap/src/protocol/alice/event_loop.rs

@@ -278,7 +278,7 @@ where
             .context("Failed to get latest rate")?;
 
         Ok(BidQuote {
-            price: rate.ask,
+            price: rate.ask(),
             max_quantity: max_buy,
         })
     }