Add Simulation::add_async_party

Signed-off-by: Denis Varlakov <denis@dfns.co>

Author: survived

round-based/src/simulation/mod.rs

@@ -248,8 +248,7 @@ where
     {
         let mut sim = Self::with_capacity(n);
         for i in 0..n {
-            let party = crate::state_machine::wrap_protocol(|party| init(i, party));
-            sim.add_party(party)
+            sim.add_async_party(|party| init(i, party))
         }
         sim
     }
@@ -282,6 +281,24 @@ where
         })
     }
 
+    /// Adds new party, defined as an async function, into the protocol
+    ///
+    /// New party will be assigned index `i = n - 1` where `n` is amount of parties in the
+    /// simulation after this party was added.
+    ///
+    /// Async function will be converted into a [state machine](crate::state_machine). Because of that,
+    /// it cannot await on any futures that aren't provided by `MpcParty` (that is given as an argument
+    /// to this function).
+    pub fn add_async_party<F>(&mut self, party: impl FnOnce(crate::state_machine::MpcParty<M>) -> F)
+    where
+        F: core::future::Future<Output = O> + 'a,
+    {
+        self.parties.push(Party::Active {
+            party: Box::new(crate::state_machine::wrap_protocol(party)),
+            wants_one_more_msg: false,
+        })
+    }
+
     /// Returns amount of parties in the simulation
     pub fn parties_amount(&self) -> usize {
         self.parties.len()