sim-lib: add clock trait to mock time with default impl

Add a trait to mock time so that when we get to using
simulation time, we don't need to refactor. At present,
this is just a wrapper over system time.

Author: carlaKC

simln-lib/src/clock.rs

@@ -0,0 +1,24 @@
+use async_trait::async_trait;
+use std::time::{Duration, SystemTime};
+use tokio::time;
+
+#[async_trait]
+pub trait Clock: Send + Sync {
+    fn now(&self) -> SystemTime;
+    async fn sleep(&self, wait: Duration);
+}
+
+/// Provides a wall clock implementation of the Clock trait.
+#[derive(Clone)]
+pub struct SystemClock {}
+
+#[async_trait]
+impl Clock for SystemClock {
+    fn now(&self) -> SystemTime {
+        SystemTime::now()
+    }
+
+    async fn sleep(&self, wait: Duration) {
+        time::sleep(wait).await;
+    }
+}

simln-lib/src/lib.rs

@@ -29,6 +29,7 @@ use self::defined_activity::DefinedPaymentActivity;
 use self::random_activity::{NetworkGraphView, RandomPaymentActivity};
 
 pub mod cln;
+pub mod clock;
 mod defined_activity;
 pub mod eclair;
 pub mod lnd;