Keanu (#7)

* simple EventBus

build.sbt

@@ -94,10 +94,18 @@ lazy val blammo = {
     .dependsOn(macaroni, lzy, friday, veil)
 }
 
+lazy val keanu =
+  project
+    .in(file("keanu"))
+    .settings(
+      name := "keanu"
+    )
+    .dependsOn(macaroni, lzy, blammo)
+
 lazy val example =
   project
     .in(file("example"))
-    .dependsOn(macaroni, lzy, spider, piggy, friday, veil, blammo)
+    .dependsOn(macaroni, lzy, spider, piggy, friday, veil, blammo, keanu)
     .settings(
       name := "example",
       libraryDependencies ++= Seq( // Examples and tests are allowed to have dependencies :-)

example/src/main/scala/app/wishingtree/KeanuExample.scala

@@ -0,0 +1,26 @@
+package app.wishingtree
+
+import dev.wishingtree.branch.keanu.eventbus.{EventBus, EventMessage, Subscriber}
+
+object IntEventBus extends EventBus[Int]
+
+object KeanuExample extends Subscriber[Int] { self =>
+
+  override def onMessage(msg: Int): Unit =
+    println(s"Got Int = $msg")
+
+  def main(args: Array[String]): Unit = {
+
+    IntEventBus.subscribe(self, _.payload > 5)
+    IntEventBus.subscribe(self, _.payload % 2 == 0)
+
+    IntEventBus.subscribe((msg: Int) => println(s"Got message $msg"))
+
+    IntEventBus.publish(EventMessage[Int]("tinyInts", 4))
+    IntEventBus.publish(EventMessage[Int]("tinyInts", 6))
+    IntEventBus.publish(EventMessage[Int]("tinyInts", 10))
+    IntEventBus.publish(EventMessage[Int]("tinyInts", 9))
+
+  }
+
+}

keanu/src/main/scala/dev/wishingtree/branch/keanu/eventbus/EventBus.scala

@@ -0,0 +1,54 @@
+package dev.wishingtree.branch.keanu.eventbus
+
+import java.util
+import java.util.UUID
+import scala.collection.mutable
+import scala.collection.mutable.ArrayBuffer
+import scala.util.Try
+
+trait EventBus[T] {
+
+  private case class Subscription(
+      id: UUID,
+      subscriber: Subscriber[T],
+      filter: EventMessage[T] => Boolean
+  )
+
+  private val subscribers: mutable.ArrayBuffer[Subscription] =
+    ArrayBuffer.empty
+
+  def publish(msg: EventMessage[T]): Unit = synchronized {
+    subscribers.foreach { sub =>
+      if sub.filter(msg) then Try(sub.subscriber.onMessage(msg.payload))
+    }
+  }
+
+  def subscribe(subscriber: Subscriber[T]): UUID =
+    synchronized {
+      val sub = Subscription(UUID.randomUUID(), subscriber, _ => true)
+      subscribers.addOne(sub)
+      sub.id
+    }
+
+  def subscribe(
+      subscriber: Subscriber[T],
+      filter: EventMessage[T] => Boolean
+  ): UUID = {
+    synchronized {
+      val sub = Subscription(UUID.randomUUID(), subscriber, filter)
+      subscribers.addOne(sub)
+      sub.id
+    }
+  }
+
+  def unsubscribe(subscriber: Subscriber[T]): Unit =
+    synchronized {
+      subscribers.filterInPlace(sub => sub.subscriber != subscriber)
+    }
+
+  def unsubscribe(ids: UUID*): Unit =
+    synchronized {
+      subscribers.filterInPlace(sub => !ids.contains(sub.id))
+    }
+}
+

keanu/src/main/scala/dev/wishingtree/branch/keanu/eventbus/EventMessage.scala

@@ -0,0 +1,3 @@
+package dev.wishingtree.branch.keanu.eventbus
+
+case class EventMessage[T](topic: String, payload: T)

keanu/src/main/scala/dev/wishingtree/branch/keanu/eventbus/Subscriber.scala

@@ -0,0 +1,5 @@
+package dev.wishingtree.branch.keanu.eventbus
+
+trait Subscriber[T] {
+  def onMessage(msg: T): Unit
+}

site/src/SUMMARY.md

@@ -8,4 +8,5 @@
 - [Friday](./friday/index.md)
 - [Macaroni](./macaroni/index.md)
 - [Veil](./veil/index.md)
-- [Blammo](./blammo/index.md)
+- [Blammo](./blammo/index.md)
+- [Keanu](./keanu/index.md)

site/src/index.md

@@ -16,12 +16,12 @@ things done quickly! Think of it as the framework for your side-project, not you
 - **Macaroni** - Some re-usable helpers and meta-programming utilities.
 - **Veil** - `.env` / (Json based) Config utilities.
 - **Blammo** - It's better than bad, it's (Json) logging!
+- **Keanu** - A simple *typed* EventBus implementation, and where Actors will eventually live
 
 ... and *more to come*!
 
 A list of other things important to this framework's goals are (but not limited to):
 
 - Web Sockets
-- Event Bus
 - Actors, even if it kills me.
 - (HTML) Templating

site/src/keanu/index.md

@@ -0,0 +1,12 @@
+# Keanu
+
+This module currently contains a simple *typed* EventBus.
+
+Have an object extend `EventBus[T]` for your type, e.g.
+
+```scala 3
+object IntEventBus extends EventBus[Int]
+```
+
+Then, you can have some implementation extend `Subsciber[T]` and subscribe, or pass in an anonymous implementation (e.g.
+`IntEventBus.subscribe((msg: Int) => println(s"Got message $msg"))`)