Add simple chat based on EventMachine with Couchbase logger

Change-Id: If0a80f31d87ba632ff6510e2175c340dfcc876ba
Reviewed-on: http://review.couchbase.org/24480
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>

examples/chat-em/Gemfile

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+source :rubygems
+
+gem 'eventmachine'
+
+# couchbase dependencies
+gem 'yaji'
+gem 'multi_json'

examples/chat-em/README.markdown

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+# Chat Demo
+
+This is simple demo of the chat built on EventMachine, and using
+Couchbase to store logs.
+
+# Quick Start and Usage
+
+Navigate to the example directory and install dependencies:
+
+    $ cd examples/chat-em
+    $ bundle install
+
+Execute the server
+
+    $ ruby ./server.rb
+    Hi, this is simple chat server based on EventMachine.
+    To join, just use your telnet or netcat clients to connect to
+    port 9999 on this machine. Press Ctrl-C to stop it.
+
+Use telnet to join the chat
+
+    $ telnet localhost 9999
+    Trying 127.0.0.1...
+    Connected to localhost.
+    Escape character is '^]'.
+    *** What is your name?
+    avsej
+    *** Hi, avsej!
+    Hi everyone in this chat
+
+The server will broadcast all your messages and record any event to
+the Couchbase server. If your server hosted not on the localhost or
+using bucket different from "default" you might want to change the
+connection options at the bottom of the `server.rb`, for example in
+this case it will connect to the bucket "protected" with password
+"secret".
+
+    Couchbase.connection_options = {
+                :async => true,
+                :engine => :eventmachine,
+                :bucket => "protected",
+                :password => "secret"
+              }
+
+Happy hacking!

examples/chat-em/server.rb

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+#!/usr/bin/env ruby
+["/../../lib", "/.."].each do |path|
+  $LOAD_PATH.unshift(File.expand_path(File.dirname(__FILE__) + path))
+end
+
+require 'bundler'
+Bundler.require
+
+require 'couchbase'
+
+class ChatServer < EM::Connection
+
+  @@clients = []
+
+  def log(message, author = nil)
+    Couchbase.bucket.incr("log:key", :initial => 1) do |res|
+      entry = {
+        'time' => Time.now.utc,
+        'author' => author || "[system]",
+        'message' => message
+      }
+      Couchbase.bucket.set("log:#{res.value}", entry)
+    end
+  end
+
+  def post_init
+    @username = nil
+    send_data("*** What is your name?\n")
+  end
+
+  def receive_data(data)
+    if @username
+      broadcast(data.strip, @username)
+    else
+      name = data.gsub(/\s+|[\[\]]/, '').strip[0..20]
+      if name.empty?
+        send_data("*** What is your name?\n")
+      else
+        @username = name
+        @@clients.push(self)
+        broadcast("#{@username} has joined")
+        send_data("*** Hi, #{@username}!\n")
+      end
+    end
+  end
+
+  def unbind
+    @@clients.delete(self)
+    broadcast("#{@username} has left") if @username
+  end
+
+  def broadcast(message, author = nil)
+    prefix = author ? "<#{@username}>" : "***"
+    log(message, author)
+    @@clients.each do |client|
+      unless client == self
+        client.send_data("#{prefix} #{message}\n")
+      end
+    end
+  end
+
+end
+
+EventMachine.run do
+  # hit Control + C to stop
+  Signal.trap("INT")  { EventMachine.stop }
+  Signal.trap("TERM") { EventMachine.stop }
+
+  Couchbase.connection_options = {:async => true, :engine => :eventmachine}
+  Couchbase.bucket.on_connect do |res|
+    if res.success?
+      puts(<<-MOTD.gsub(/^\s+/, ''))
+        Hi, this is simple chat server based on EventMachine.
+        To join, just use your telnet or netcat clients to connect to
+        port 9999 on this machine. Press Ctrl-C to stop it.
+      MOTD
+      EventMachine.start_server("0.0.0.0", 9999, ChatServer)
+    else
+      puts "Cannot connect to Couchbase Server: #{res.error}"
+    end
+  end
+end