Copy euph-api-related parts from cove

Also includes the required dependencies and some minor changes to the
module structure, as well as all the clippy and rustc warnings.

src/replies.rs

@@ -0,0 +1,68 @@
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::result;
+use std::time::Duration;
+
+use tokio::sync::oneshot::{self, Receiver, Sender};
+use tokio::time;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("timed out")]
+    TimedOut,
+    #[error("canceled")]
+    Canceled,
+}
+
+pub type Result<T> = result::Result<T, Error>;
+
+#[derive(Debug)]
+pub struct PendingReply<R> {
+    timeout: Duration,
+    result: Receiver<R>,
+}
+
+impl<R> PendingReply<R> {
+    pub async fn get(self) -> Result<R> {
+        let result = time::timeout(self.timeout, self.result).await;
+        match result {
+            Err(_) => Err(Error::TimedOut),
+            Ok(Err(_)) => Err(Error::Canceled),
+            Ok(Ok(value)) => Ok(value),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Replies<I, R> {
+    timeout: Duration,
+    pending: HashMap<I, Sender<R>>,
+}
+
+impl<I: Eq + Hash, R> Replies<I, R> {
+    pub fn new(timeout: Duration) -> Self {
+        Self {
+            timeout,
+            pending: HashMap::new(),
+        }
+    }
+
+    pub fn wait_for(&mut self, id: I) -> PendingReply<R> {
+        let (tx, rx) = oneshot::channel();
+        self.pending.insert(id, tx);
+        PendingReply {
+            timeout: self.timeout,
+            result: rx,
+        }
+    }
+
+    pub fn complete(&mut self, id: &I, result: R) {
+        if let Some(tx) = self.pending.remove(id) {
+            let _ = tx.send(result);
+        }
+    }
+
+    pub fn purge(&mut self) {
+        self.pending.retain(|_, tx| !tx.is_closed());
+    }
+}