Working on new (blocking) event machine.

The new event machine will be used for loose coupling and handle the
communications between the services:

1) Block pool finds blocks which "links" with our current canonical
chain
2) Posts the blocks on to the event machine
3) State manager receives blocks & processes them
4) Broadcasts new post block event

eventer/eventer.go

@@ -0,0 +1,79 @@
+package eventer
+
+// Basic receiver interface.
+type Receiver interface {
+	Send(Event)
+}
+
+// Receiver as channel
+type Channel chan Event
+
+func (self Channel) Send(ev Event) {
+	self <- ev
+}
+
+// Receiver as function
+type Function func(ev Event)
+
+func (self Function) Send(ev Event) {
+	self(ev)
+}
+
+type Event struct {
+	Type string
+	Data interface{}
+}
+
+type Channels map[string][]Receiver
+
+type EventMachine struct {
+	channels Channels
+}
+
+func New() *EventMachine {
+	return &EventMachine{
+		channels: make(Channels),
+	}
+}
+
+func (self *EventMachine) add(typ string, r Receiver) {
+	self.channels[typ] = append(self.channels[typ], r)
+}
+
+// Generalised methods for the known receiver types
+// * Channel
+// * Function
+func (self *EventMachine) On(typ string, r interface{}) {
+	if eventFunc, ok := r.(func(Event)); ok {
+		self.RegisterFunc(typ, eventFunc)
+	} else if eventChan, ok := r.(Channel); ok {
+		self.RegisterChannel(typ, eventChan)
+	} else {
+		panic("Invalid type for EventMachine::On")
+	}
+}
+
+func (self *EventMachine) RegisterChannel(typ string, c Channel) {
+	self.add(typ, c)
+}
+
+func (self *EventMachine) RegisterFunc(typ string, f Function) {
+	self.add(typ, f)
+}
+
+func (self *EventMachine) Register(typ string) Channel {
+	c := make(Channel, 1)
+	self.add(typ, c)
+
+	return c
+}
+
+func (self *EventMachine) Post(typ string, data interface{}) {
+	if self.channels[typ] != nil {
+		ev := Event{typ, data}
+		for _, receiver := range self.channels[typ] {
+			// Blocking is OK. These are internals and need to be handled
+			receiver.Send(ev)
+		}
+	}
+}

eventer/eventer_test.go

@@ -0,0 +1,66 @@
+package eventer
+
+import "testing"
+
+func TestChannel(t *testing.T) {
+	eventer := New(nil)
+
+	c := make(Channel, 1)
+	eventer.RegisterChannel("test", c)
+	eventer.Post("test", "hello world")
+
+	res := <-c
+
+	if res.Data.(string) != "hello world" {
+		t.Error("Expected event with data 'hello world'. Got", res.Data)
+	}
+}
+
+func TestFunction(t *testing.T) {
+	eventer := New(nil)
+
+	var data string
+	eventer.RegisterFunc("test", func(ev Event) {
+		data = ev.Data.(string)
+	})
+	eventer.Post("test", "hello world")
+
+	if data != "hello world" {
+		t.Error("Expected event with data 'hello world'. Got", data)
+	}
+}
+
+func TestRegister(t *testing.T) {
+	eventer := New(nil)
+
+	c := eventer.Register("test")
+	eventer.Post("test", "hello world")
+
+	res := <-c
+
+	if res.Data.(string) != "hello world" {
+		t.Error("Expected event with data 'hello world'. Got", res.Data)
+	}
+}
+
+func TestOn(t *testing.T) {
+	eventer := New(nil)
+
+	c := make(Channel, 1)
+	eventer.On("test", c)
+
+	var data string
+	eventer.On("test", func(ev Event) {
+		data = ev.Data.(string)
+	})
+	eventer.Post("test", "hello world")
+
+	res := <-c
+	if res.Data.(string) != "hello world" {
+		t.Error("Expected channel event with data 'hello world'. Got", res.Data)
+	}
+
+	if data != "hello world" {
+		t.Error("Expected function event with data 'hello world'. Got", data)
+	}
+}