Actors and Messages in Ruby

actors_and_messages.rb

require "colorize"

REGISTRY = {}
DEBUG = false
SLEEP = 0.5

def register(id)
  mailbox = Queue.new
  Thread.current[:process_id] = id
  REGISTRY[id] = mailbox
  [id, mailbox]
end

def mailbox(id)
  mailbox = REGISTRY[id]
  unless mailbox
    raise "Error getting mailbox: unrecognized id #{id}"
  end
  mailbox
end

def new_id
  @current_id ||= 0
  @current_id += 1
end

def log(str)
  return nil unless DEBUG
  puts str
end

def current_id
  Thread.current[:process_id]
end

def msg_send(to:, from:, msg:)
  puts "sending <#{msg}> to #{to}, from #{from}".magenta
  mailbox(to) << { from: from, body: msg }
  true
end

def cast(to:, from:, msg:)
  msg_send(to: to, from: from, msg: msg)
end

def call(to:, from:, msg:)
  msg_send(to: to, from: from, msg: msg)
  receive(block: true)
end


def receive(block: nil)
  if block.nil?
    non_block = (current_id == :main)
  else
    non_block = !block
  end

  mailbox(current_id).pop(non_block)
rescue ThreadError
  nil
end


def spawn(&block)
  id = new_id

  Thread.new do
    _id, mailbox = register(id)

    loop do
      log "-- id: #{id}, pending messages: #{mailbox.length}"
      message = receive
      log "-- id: #{id} received message: #{message}"
      reply_to = message[:from]
      body = message[:body]

      begin
        sleep SLEEP
        result = block.call(body, id, reply_to)
        if result != :noreply
          msg_send(to: reply_to, from: id, msg: result)
        end
      rescue => e
        msg_send(to: reply_to, from: id, msg: e)
      end
    end
  end

  id
end


@aa = spawn do |msg|
  msg.upcase + "?"
end

@bb = spawn do |msg|
  msg.reverse
end

@cc = spawn do |msg, own_id, from|
  puts "received msg: #{msg} from: #{from}".yellow
  if msg == "start"
    msg_send(to: @aa, from: own_id, msg: "tommaso")
    msg_send(to: @bb, from: own_id, msg: "tommaso")
  end
  :noreply
end

@ping = spawn do |msg, own_id, from|
  puts "I'm PING, I've received #{msg}."
  target = (msg.is_a?(Hash) && msg[:reply_to]) || from
  msg_send to: target, from: own_id, msg: "PING"
  :noreply
end

@pong = spawn do |msg, own_id, from|
  puts "I'm PONG, I've received #{msg}."
  target = (msg.is_a?(Hash) && msg[:reply_to]) || from
  msg_send to: target, from: own_id, msg: "PONG"
  :noreply
end

# -------------------------
register(:main)

def start
  msg_send to: @cc, from: :main, msg: "start"
end

# start
# 10.times { |i| msg_send to: @aa, from: :main, msg: "ciao#{i}" }
# msg_send to: @ping, from: :main, msg: { reply_to: @pong }
# cast to: @bb, from: :main, msg: "tommaso"
# call to: @bb, from: :main, msg: "tommaso"