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require 'logger'
require 'thread'
require 'timeout'
require 'set'

module Celluloid
  extend self # expose all instance methods as singleton methods

  SHUTDOWN_TIMEOUT = 120 # How long actors have to terminate

  class << self
    attr_accessor :logger # Thread-safe logger class
    attr_accessor :task_class # Default task type to use

    def included(klass)
      klass.send :extend, ClassMethods
      klass.send :include, InstanceMethods
    end

    # Are we currently inside of an actor?
    def actor?
      !!Thread.current[:actor]
    end

    # Generate a Universally Unique Identifier
    def uuid
      UUID.generate
    end

    # Obtain the number of CPUs in the system
    def cores
      CPUCounter.cores
    end
    alias_method :cpus, :cores
    alias_method :ncpus, :cores

    # Define an exception handler for actor crashes
    def exception_handler(&block)
      Logger.exception_handler(&block)
    end

    # Shut down all running actors
    def shutdown
      Timeout.timeout(SHUTDOWN_TIMEOUT) do
        actors = Actor.all
        Logger.info "Terminating #{actors.size} actors..." if actors.size > 0

        # Attempt to shut down the supervision tree, if available
        Supervisor.root.terminate if Supervisor.root

        # Actors cannot self-terminate, you must do it for them
        Actor.all.each do |actor|
          begin
            actor.terminate!
          rescue DeadActorError, MailboxError
          end
        end

        Actor.all.each do |actor|
          begin
            Actor.join(actor)
          rescue DeadActorError, MailboxError
          end
        end

        Logger.info "Shutdown completed cleanly"
      end
    end
  end

  # Terminate all actors at exit
  at_exit { shutdown }

  # Class methods added to classes which include Celluloid
  module ClassMethods
    # Create a new actor
    def new(*args, &block)
      proxy = Actor.new(allocate, actor_options).proxy
      proxy._send_(:initialize, *args, &block)
      proxy
    end
    alias_method :spawn, :new

    # Create a new actor and link to the current one
    def new_link(*args, &block)
      raise NotActorError, "can't link outside actor context" unless Celluloid.actor?

      proxy = Actor.new(allocate, actor_options).proxy
      Actor.link(proxy)
      proxy._send_(:initialize, *args, &block)
      proxy
    end
    alias_method :spawn_link, :new_link

    # Create a supervisor which ensures an instance of an actor will restart
    # an actor if it fails
    def supervise(*args, &block)
      Supervisor.supervise(self, *args, &block)
    end

    # Create a supervisor which ensures an instance of an actor will restart
    # an actor if it fails, and keep the actor registered under a given name
    def supervise_as(name, *args, &block)
      Supervisor.supervise_as(name, self, *args, &block)
    end

    # Create a new pool of workers. Accepts the following options:
    #
    # * size: how many workers to create. Default is worker per CPU core
    # * args: array of arguments to pass when creating a worker
    #
    def pool(options = {})
      PoolManager.new(self, options)
    end

    # Same as pool, but links to the pool manager
    def pool_link(options = {})
      PoolManager.new_link(self, options)
    end

    # Run an actor in the foreground
    def run(*args, &block)
      new(*args, &block).join
    end

    # Trap errors from actors we're linked to when they exit
    def trap_exit(callback)
      @exit_handler = callback.to_sym
    end

    # Configure a custom mailbox factory
    def use_mailbox(klass = nil, &block)
      if block
        @mailbox_factory = block
      else
        @mailbox_factory = proc { klass.new }
      end
    end

    # Define the default task type for this class
    def task_class(klass)
      @task_class = klass
    end

    # Mark methods as running exclusively
    def exclusive(*methods)
      if methods.empty?
        @exclusive_methods = :all
      elsif @exclusive_methods != :all
        @exclusive_methods ||= Set.new
        @exclusive_methods.merge methods.map(&:to_sym)
      end
    end

    # Create a mailbox for this actor
    def mailbox_factory
      if defined?(@mailbox_factory)
        @mailbox_factory.call
      elsif superclass.respond_to? :mailbox_factory
        superclass.mailbox_factory
      else
        Mailbox.new
      end
    end

    # Configuration options for Actor#new
    def actor_options
      {
        :mailbox => mailbox_factory,
        :exit_handler => @exit_handler,
        :exclusive_methods => @exclusive_methods,
        :task_class => @task_class
      }
    end

    def ===(other)
      other.kind_of? self
    end
  end

  # These are methods we don't want added to the Celluloid singleton but to be
  # defined on all classes that use Celluloid
  module InstanceMethods
    # Obtain the Ruby object the actor is wrapping. This should ONLY be used
    # for a limited set of use cases like runtime metaprogramming. Interacting
    # directly with the wrapped object foregoes any kind of thread safety that
    # Celluloid would ordinarily provide you, and the object is guaranteed to
    # be shared with at least the actor thread. Tread carefully.
    def wrapped_object; self; end

    def inspect
      str = "#<Celluloid::Actor(#{self.class}:0x#{object_id.to_s(16)})"
      ivars = instance_variables.map do |ivar|
        "#{ivar}=#{instance_variable_get(ivar).inspect}"
      end

      str << " " << ivars.join(' ') unless ivars.empty?
      str << ">"
    end

    # Process async calls via method_missing
    def method_missing(meth, *args, &block)
      # bang methods are async calls
      if meth.to_s.match(/!$/)
        unbanged_meth = meth.to_s.sub(/!$/, '')
        args.unshift unbanged_meth

        call = AsyncCall.new(:__send__, args, block)
        begin
          Thread.current[:actor].mailbox << call
        rescue MailboxError
          # Silently swallow asynchronous calls to dead actors. There's no way
          # to reliably generate DeadActorErrors for async calls, so users of
          # async calls should find other ways to deal with actors dying
          # during an async call (i.e. linking/supervisors)
        end

        return
      end

      super
    end
  end

  #
  # The following methods are available on both the Celluloid singleton and
  # directly inside of all classes that include Celluloid
  #

  # Is this actor alive?
  def alive?
    Thread.current[:actor].alive?
  end

  # Raise an exception in caller context, but stay running
  def abort(cause)
    cause = case cause
      when String then RuntimeError.new(cause)
      when Exception then cause
      else raise TypeError, "Exception object/String expected, but #{cause.class} received"
    end
    raise AbortError.new(cause)
  end

  # Terminate this actor
  def terminate
    Thread.current[:actor].terminate
  end

  # Send a signal with the given name to all waiting methods
  def signal(name, value = nil)
    Thread.current[:actor].signal name, value
  end

  # Wait for the given signal
  def wait(name)
    Thread.current[:actor].wait name
  end

  # Obtain the current_actor
  def current_actor
    Actor.current
  end

  # Obtain the name of the current actor
  def name
    Actor.name
  end

  # Obtain the running tasks for this actor
  def tasks
    Thread.current[:actor].tasks.to_a
  end

  # Obtain the Celluloid::Links for this actor
  def links
    Thread.current[:actor].links
  end

  # Watch for exit events from another actor
  def monitor(actor)
    Actor.monitor(actor)
  end

  # Stop waiting for exit events from another actor
  def unmonitor(actor)
    Actor.unmonitor(actor)
  end

  # Link this actor to another, allowing it to crash or react to errors
  def link(actor)
    Actor.link(actor)
  end

  # Remove links to another actor
  def unlink(actor)
    Actor.unlink(actor)
  end

  # Are we monitoring another actor?
  def monitoring?(actor)
    Actor.monitoring?(actor)
  end

  # Is this actor linked to another?
  def linked_to?(actor)
    Actor.linked_to?(actor)
  end

  # Receive an asynchronous message via the actor protocol
  def receive(timeout = nil, &block)
    actor = Thread.current[:actor]
    if actor
      actor.receive(timeout, &block)
    else
      Thread.mailbox.receive(timeout, &block)
    end
  end

  # Sleep letting the actor continue processing messages
  def sleep(interval)
    actor = Thread.current[:actor]
    if actor
      actor.sleep(interval)
    else
      Kernel.sleep interval
    end
  end

  # Run given block in an exclusive mode: all synchronous calls block the whole
  # actor, not only current message processing.
  def exclusive(&block)
    Thread.current[:actor].exclusive(&block)
  end

  # Are we currently exclusive
  def exclusive?
    actor = Thread.current[:actor]
    actor && actor.exclusive?
  end

  # Call a block after a given interval, returning a Celluloid::Timer object
  def after(interval, &block)
    Thread.current[:actor].after(interval, &block)
  end

  # Call a block every given interval, returning a Celluloid::Timer object
  def every(interval, &block)
    Thread.current[:actor].every(interval, &block)
  end

  # Perform a blocking or computationally intensive action inside an
  # asynchronous thread pool, allowing the caller to continue processing other
  # messages in its mailbox in the meantime
  def defer(&block)
    # This implementation relies on the present implementation of
    # Celluloid::Future, which uses a thread from InternalPool to run the block
    Future.new(&block).value
  end

  # Handle async calls within an actor itself
  def async(meth, *args, &block)
    Actor.async Thread.current[:actor].mailbox, meth, *args, &block
  end

  # Handle calls to future within an actor itself
  def future(meth, *args, &block)
    Actor.future Thread.current[:actor].mailbox, meth, *args, &block
  end
end

require 'celluloid/version'
require 'celluloid/actor_proxy'
require 'celluloid/calls'
require 'celluloid/core_ext'
require 'celluloid/cpu_counter'
require 'celluloid/fiber'
require 'celluloid/fsm'
require 'celluloid/internal_pool'
require 'celluloid/links'
require 'celluloid/logger'
require 'celluloid/mailbox'
require 'celluloid/method'
require 'celluloid/receivers'
require 'celluloid/registry'
require 'celluloid/responses'
require 'celluloid/signals'
require 'celluloid/system_events'
require 'celluloid/task'
require 'celluloid/thread_handle'
require 'celluloid/uuid'

require 'celluloid/actor'
require 'celluloid/future'
require 'celluloid/pool_manager'
require 'celluloid/supervision_group'
require 'celluloid/supervisor'
require 'celluloid/notifications'

require 'celluloid/boot'
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