From 2c10e19f5804868e753fc0f883784603b48842ec Mon Sep 17 00:00:00 2001
From: Alex Bramley <a.bramley@gmail.com>
Date: Wed, 27 Jul 2011 16:54:49 +0100
Subject: [PATCH] More abstracted event registry.

---
 event/registry.go | 114 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 event/registry.go

diff --git a/event/registry.go b/event/registry.go
new file mode 100644
index 0000000..5a2ad6b
--- /dev/null
+++ b/event/registry.go
@@ -0,0 +1,114 @@
+package registry
+
+import (
+	"container/list"
+	"strings"
+	"sync/atomic"
+	"sync"
+)
+
+type HandlerID uint32
+type Handler struct {
+	Run func(...interface{})
+	ID	HandlerID
+}
+
+var hidCounter uint32 = 0
+
+func NewHandlerID() HandlerID {
+	return HandlerID(atomic.AddUint32(&hidCounter, 1))
+}
+
+func NewHandler(h func(...interface{})) *Handler {
+	return &Handler{h, NewHandlerID()}
+}
+
+type EventRegistry interface {
+	AddHandler(name string, h *Handler)
+	DelHandler(h *Handler)
+	Dispatch(name string, ev ...interface{})
+	ClearEvents(name string)
+}
+
+type registry struct {
+	// Event registry as a lockable map of linked-lists
+	sync.RWMutex
+	events	   map[string]*list.List
+	Dispatcher func(r *registry, name string, ev ...interface{})
+}	
+
+func NewRegistry() *registry {
+	r := &registry{events: make(map[string]*list.List)}
+	r.Parallel()
+	return r
+}
+
+func (r *registry) AddHandler(name string, h *Handler) {
+	name = strings.ToLower(name)
+	r.Lock()
+	defer r.Unlock()
+	if _, ok := r.events[name]; !ok {
+		r.events[name] = list.New()
+	}
+	for e := r.events[name].Front(); e != nil; e = e.Next() {
+		// Check we're not adding a duplicate handler to this event
+		if e.Value.(*Handler).ID == h.ID {
+			return
+		}
+	}
+	r.events[name].PushBack(h)
+}
+
+func (r *registry) DelHandler(h *Handler) {
+	// This is a bit brute-force. Don't add too many handlers!
+	r.Lock()
+	defer r.Unlock()
+	for _, l := range r.events {
+		for e := l.Front(); e != nil; e = e.Next() {
+			if e.Value.(*Handler).ID == h.ID {
+				l.Remove(e)
+			}
+		}
+	}
+}
+
+func (r *registry) Dispatch(name string, ev ...interface{}) {
+	r.Dispatcher(r, name, ev)
+}
+
+func (r *registry) Parallel() {
+	r.Dispatcher = (*registry).parallelDispatch
+}
+
+func (r *registry) Serial() {
+	r.Dispatcher = (*registry).serialDispatch
+}
+
+func (r *registry) parallelDispatch(name string, ev ...interface{}) {
+	name = strings.ToLower(name)
+	r.RLock()
+	defer r.RUnlock()
+	if l, ok := r.events[name]; ok {
+		for e := l.Front(); e != nil; e = e.Next() {
+			h := e.Value.(*Handler)
+			go h.Run(ev)
+		}
+	}
+}
+
+func (r *registry) serialDispatch(name string, ev ...interface{}) {
+	name = strings.ToLower(name)
+	r.RLock()
+	defer r.RUnlock()
+	if l, ok := r.events[name]; ok {
+		hlist := make([]*Handler, 0, l.Len())
+		for e := l.Front(); e != nil; e = e.Next() {
+			hlist = append(hlist, e.Value.(*Handler))
+		}
+		go func() {
+			for _, h := range hlist {
+				h.Run(ev)
+			}
+		}()
+	}
+}