initial commit

utils/bus.rb

@@ -0,0 +1,57 @@
+class EventBus
+  def initialize
+    # store callbacks with owner: {event => [ {callback:, owner:} ] }
+    @events = Hash.new { |h, k| h[k] = [] }
+    @retrievable_events = {}
+  end
+
+  # Emit an event
+  def emit(event, *args)
+    @events[event].each do |h|
+      h[:callback].call(*args)
+    end
+  end
+
+  # Subscribe to an event
+  def on(event, owner: nil, &callback)
+    owner ||= callback.binding.eval("self")
+    @events[event] << { callback: callback, owner: owner }
+  end
+
+  # Subscribe to an event that should only be called once
+  def once(event, owner = nil, &callback)
+    wrapper = nil
+    wrapper = proc do |*args|
+      callback.call(*args)
+      off(event, &wrapper)
+    end
+    on(event, owner: owner, &wrapper)
+  end
+
+  def off(event, &callback)
+    @events[event].reject! { |h| h[:callback] == callback }
+  end
+
+  # Register a retrievable event (only one allowed)
+  def on_retrievable(event, owner = nil, &callback)
+    owner ||= callback.binding.eval("self")
+    @retrievable_events[event] = { callback: callback, owner: owner }
+  end
+
+  # Get data from a retrievable event
+  def get(event, *args)
+    if @retrievable_events[event]
+      @retrievable_events[event][:callback].call(*args)
+    else
+      nil
+    end
+  end
+
+  # Unsubscribe from an object's events
+  def unlisten_owner(owner)
+    @events.each do |event, handlers|
+      handlers.reject! { |h| h[:owner] == owner }
+    end
+    @retrievable_events.delete_if { |_, h| h[:owner] == owner }
+  end
+end