create an mqtt_dummy that sends string every second

src/mqtt_dummy.gleam

@@ -0,0 +1,48 @@
+import gleam/erlang/process
+import gleam/list
+import gleam/otp/actor
+
+pub type Subscriber =
+  process.Subject(String)
+
+pub type Message {
+  Subscribe(subscriber: Subscriber)
+  Proc
+}
+
+pub type Subscribers =
+  List(Subscriber)
+
+fn handle_message(
+  subscribers: Subscribers,
+  message: Message,
+) -> actor.Next(Subscribers, Message) {
+  case message {
+    Subscribe(subscriber) -> {
+      let new_subscribers = [subscriber, ..subscribers]
+      actor.continue(new_subscribers)
+    }
+    Proc -> {
+      list.each(subscribers, fn(subscriber) {
+        process.send(subscriber, "Hello from dummy mqtt action")
+      })
+      actor.continue(subscribers)
+    }
+  }
+}
+
+// Subscribe to receive ticks from the dummy actor
+pub fn subscribe(actor_ref: process.Subject(Message)) -> Subscriber {
+  let mailbox = process.new_subject()
+  process.send(actor_ref, Subscribe(mailbox))
+  mailbox
+}
+
+// Start the actor
+pub fn start() -> Result(process.Subject(Message), actor.StartError) {
+  let assert Ok(started) =
+    actor.new([])
+    |> actor.on_message(handle_message)
+    |> actor.start
+  Ok(started.data)
+}