From 8b0943a7b24e317e7f1f23d08232c05abb580a07 Mon Sep 17 00:00:00 2001
From: Tamer Tas <contact@tmrts.com>
Date: Tue, 12 Apr 2016 06:11:51 +0300
Subject: [PATCH] Add pub/sub messaging pattern

---
 README.md                      |  2 +-
 messaging/publish_subscribe.md | 80 ++++++++++++++++++++++++++++++++++
 publish_subscribe.go           | 62 --------------------------
 3 files changed, 81 insertions(+), 63 deletions(-)
 create mode 100644 messaging/publish_subscribe.md
 delete mode 100644 publish_subscribe.go

diff --git a/README.md b/README.md
index 79960a0..ce563ea 100644
--- a/README.md
+++ b/README.md
@@ -80,7 +80,7 @@ __Messaging Patterns__:
 | [Fan-In](fan/fan_in.go) | Funnels tasks to a work sink (e.g. server) |
 | [Fan-Out](fan/fan_out.go) | Distributes tasks amongs workers |
 | [Futures & Promises](futures_promises.go) | Acts as a place-holder of a result that is initally unknown for synchronization purposes |
-| [Publish/Subscribe](publish_subscribe.go) | Passes information to a collection of recipients who subscribed to a topic |
+| [Publish/Subscribe](messaging/publish_subscribe.md) | Passes information to a collection of recipients who subscribed to a topic |
 | [Push & Pull](push_pull.go) | Distributes messages to multiple workers, arranged in a pipeline |
 
 __Stability Patterns__:
diff --git a/messaging/publish_subscribe.md b/messaging/publish_subscribe.md
new file mode 100644
index 0000000..efb46b5
--- /dev/null
+++ b/messaging/publish_subscribe.md
@@ -0,0 +1,80 @@
+Publish & Subscribe Messaging Pattern
+============
+Publish-Subscribe is a messaging pattern used to communicate messages between 
+different components without these components knowing anything about each other's identity.
+
+It is similar to the Observer behavioral design pattern. 
+The fundamental design principals of both Observer and Publish-Subscribe is the decoupling of
+those interested in being informed about `Event Messages` from the informer (Observers or Publishers).
+Meaning that you don't have to program the messages to be sent directly to specific receivers.
+
+To accomplish this, an intermediary, called a "message broker" or "event bus", 
+receives published messages, and then routes them on to subscribers.
+
+
+There are three components **messages**, **topics**, **users**.
+
+```go
+type Message struct {
+    // Contents
+}
+
+
+type Subscription struct {
+	ch chan<- Message
+
+	Inbox chan Message
+}
+
+func (s *Subscription) Publish(msg Message) error {
+	if _, ok := ch; !ok {
+		return errors.New("Topic has been closed")
+	}
+
+	ch <- msg
+
+	return nil
+}
+```
+
+```go
+type Topic struct {
+	Subscribers    []Session
+	MessageHistory []Message
+}
+
+func (t *Topic) Subscribe(uid uint64) (Subscription, error) {
+    // Get session and create one if it's the first
+
+    // Add session to the Topic & MessageHistory
+
+    // Create a subscription
+}
+
+func (t *Topic) Unsubscribe(Subscription) error {
+	// Implementation
+}
+
+func (t *Topic) Delete() error {
+	// Implementation
+}
+```
+
+```go
+type User struct {
+    ID uint64
+    Name string
+}
+
+type Session struct {
+    User User
+    Timestamp time.Time
+}
+```
+
+Improvements
+============
+Events can be published in a parallel fashion by utilizing stackless goroutines.
+
+Performance can be improved by dealing with straggler subscribers
+by using a buffered inbox and you stop sending events once the inbox is full.
diff --git a/publish_subscribe.go b/publish_subscribe.go
deleted file mode 100644
index 441e01b..0000000
--- a/publish_subscribe.go
+++ /dev/null
@@ -1,62 +0,0 @@
-package main
-
-import (
-	"errors"
-	"time"
-)
-
-var (
-	ErrTopicClosed = errors.New("Topic has been closed")
-)
-
-// Message
-type Message string
-
-// Topic
-type Topic struct {
-	Subscribers    []Authentication
-	MessageHistory []struct {
-		Author    string
-		Message   Message
-		Timestamp time.Time
-	}
-}
-
-// Subscribe
-func (t *Topic) Subscribe(Authentication) (Subscription, error) {
-	// Implementation
-}
-
-// Unsubscribe
-func (t *Topic) Unsubscribe(Subscription) error {
-	// Implementation
-}
-
-// Delete
-func (t *Topic) Delete() error {
-	// Implementation
-}
-
-type Subscription struct {
-	ch chan<- Message
-
-	Inbox chan Message
-}
-
-// Publish
-func (s *Subscription) Publish(msg Message) error {
-	if _, ok := ch; !ok {
-		return ErrTopicClosed
-	}
-
-	ch <- msg
-
-	return nil
-}
-
-// Authentication
-type Authentication struct {
-}
-
-func main() {
-}