Finished getting the project to work.

Just needs clean up and commenting/documenting.

src/main.rs

@@ -4,10 +4,12 @@ mod commands;
 
 
 use std::io::Write;
+use std::pin::Pin;
+use std::future::Future;
 
+use tokio::io::AsyncWriteExt;
 use tokio::sync::{mpsc, watch};
 use tokio::time::{Duration, Interval};
-use tokio::io::AsyncWriteExt;
 
 use crate::commands::Command;
 
@@ -79,7 +81,8 @@ fn read_user_input(command_sender: mpsc::Sender<Command>,
                   else
                   {
                      let larger_seconds: u64 = seconds as u64;
-                     let delay_duration: Duration = Duration::from_secs(larger_seconds);
+                     let delay_duration: Duration =
+                        Duration::from_secs(larger_seconds);
                      match command_sender.try_send(Command::Propulsion { delay: delay_duration })
                      {
                         Ok(_) =>
@@ -106,10 +109,22 @@ fn read_user_input(command_sender: mpsc::Sender<Command>,
    Ok(())
 }
 
+///
+fn maybe_tick<'a>(interval: Option<&'a mut Interval>)
+                  -> Pin<Box<dyn Future<Output = ()> + Send + 'a>>
+{
+   match interval
+   {
+      Some(interval) => Box::pin(async move { interval.tick().await; () }),
+      None => Box::pin(std::future::pending())
+   }
+}
+
 async fn process_commands(mut command_receiver: mpsc::Receiver<Command>,
                           mut term_receiver: watch::Receiver<bool>)
                           -> IoResult<()>
 {
+   let mut propulsion_interval: Option<Interval> = None;
    let mut stdout = tokio::io::stdout();
 
    let mut running: bool = true;
@@ -124,6 +139,7 @@ async fn process_commands(mut command_receiver: mpsc::Receiver<Command>,
                 {
                    stdout.write_all(b"Received: Cancel\n").await?;
                    stdout.flush().await?;
+                   propulsion_interval = None;
                 }
 
                 Command::Propulsion { delay } =>
@@ -132,13 +148,27 @@ async fn process_commands(mut command_receiver: mpsc::Receiver<Command>,
                    writeln!(&mut buffer, "Received: {:?} delay", delay);
                    stdout.write_all(&buffer).await?;
                    stdout.flush().await?;
+
+                   propulsion_interval = Some(tokio::time::interval(delay));
+
+                   // Skip the first immediate tick
+                   if let Some(interval) = propulsion_interval.as_mut()
+                   {
+                      interval.tick().await; // skip first tick
                    }
 
-                _ => {}
+                }
              }
           }
 
-          _ = term_receiver.changed() => {
+          _ = maybe_tick(propulsion_interval.as_mut()) =>
+          {
+            stdout.write_all(b"firing now!\n").await?;
+            stdout.flush().await?;
+          }
+
+          _ = term_receiver.changed() =>
+          {
               stdout.write_all(b"Communication task received shutdown message.").await?;
                    stdout.flush().await?;
               running = *term_receiver.borrow_and_update();