From f1b354e6aa6c4b0330e35ae9011784ff1a0b01ab Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Sun, 2 Mar 2014 02:22:20 +0100
Subject: [PATCH] Reactor implemented

---
 ethutil/reactor.go      | 77 +++++++++++++++++++++++++++++++++++++++++
 ethutil/reactor_test.go | 30 ++++++++++++++++
 2 files changed, 107 insertions(+)
 create mode 100644 ethutil/reactor.go
 create mode 100644 ethutil/reactor_test.go

diff --git a/ethutil/reactor.go b/ethutil/reactor.go
new file mode 100644
index 0000000000..b3f8b9b5b7
--- /dev/null
+++ b/ethutil/reactor.go
@@ -0,0 +1,77 @@
+package ethutil
+
+import (
+	"sync"
+)
+
+type ReactorEvent struct {
+	mut   sync.Mutex
+	event string
+	chans []chan React
+}
+
+// Post the specified reactor resource on the channels
+// currently subscribed
+func (e *ReactorEvent) Post(react React) {
+	for _, ch := range e.chans {
+		go func(ch chan React) {
+			ch <- react
+		}(ch)
+	}
+}
+
+// Add a subscriber to this event
+func (e *ReactorEvent) Add(ch chan React) {
+	e.chans = append(e.chans, ch)
+}
+
+// Remove a subscriber
+func (e *ReactorEvent) Remove(ch chan React) {
+	for i, c := range e.chans {
+		if c == ch {
+			e.chans = append(e.chans[:i], e.chans[i+1:]...)
+		}
+	}
+}
+
+// Basic reactor resource
+type React struct {
+	Resource interface{}
+}
+
+// The reactor basic engine. Acts as bridge
+// between the events and the subscribers/posters
+type ReactorEngine struct {
+	patterns map[string]*ReactorEvent
+}
+
+func NewReactorEngine() *ReactorEngine {
+	return &ReactorEngine{patterns: make(map[string]*ReactorEvent)}
+}
+
+// Subscribe a channel to the specified event
+func (reactor *ReactorEngine) Subscribe(event string, ch chan React) {
+	ev := reactor.patterns[event]
+	// Create a new event if one isn't available
+	if ev == nil {
+		ev = &ReactorEvent{event: event}
+		reactor.patterns[event] = ev
+	}
+
+	// Add the channel to reactor event handler
+	ev.Add(ch)
+}
+
+func (reactor *ReactorEngine) Unsubscribe(event string, ch chan React) {
+	ev := reactor.patterns[event]
+	if ev != nil {
+		ev.Remove(ch)
+	}
+}
+
+func (reactor *ReactorEngine) Post(event string, resource interface{}) {
+	ev := reactor.patterns[event]
+	if ev != nil {
+		ev.Post(React{Resource: resource})
+	}
+}
diff --git a/ethutil/reactor_test.go b/ethutil/reactor_test.go
new file mode 100644
index 0000000000..48c2f0df35
--- /dev/null
+++ b/ethutil/reactor_test.go
@@ -0,0 +1,30 @@
+package ethutil
+
+import "testing"
+
+func TestReactorAdd(t *testing.T) {
+	engine := NewReactorEngine()
+	ch := make(chan React)
+	engine.Subscribe("test", ch)
+	if len(engine.patterns) != 1 {
+		t.Error("Expected patterns to be 1, got", len(engine.patterns))
+	}
+}
+
+func TestReactorEvent(t *testing.T) {
+	engine := NewReactorEngine()
+
+	// Buffer 1, so it doesn't block for this test
+	ch := make(chan React, 1)
+	engine.Subscribe("test", ch)
+	engine.Post("test", "hello")
+
+	value := <-ch
+	if val, ok := value.Resource.(string); ok {
+		if val != "hello" {
+			t.Error("Expected Resource to be 'hello', got", val)
+		}
+	} else {
+		t.Error("Unable to cast")
+	}
+}