ReactiveX/RxRuby

# Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

require 'thread'
require 'singleton'

module Rx
  module Subscription
    def dispose
      unsubscribe
    end
  end
  Disposable = Subscription

  class EmptySubscription

    include Subscription
    include Singleton

    def unsubscribe

    end
  end

  class AnonymousSubscription
    include Subscription

    def initialize(&unsubscribe_action)
      @unsubscribe_action = unsubscribe_action
      @gate = Mutex.new
      @unsubscribed = false
    end

    def unsubscribe
      should_unsubscribe = false
      @gate.synchronize do
        should_unsubscribe = !@unsubscribed
      end

      @unsubscribe_action.call if should_unsubscribe
    end
  end

  # Provides a set of class methods for creating Disposables.
  module Subscription

    # Creates a subscription object that invokes the specified action when unsubscribed.
    def self.create(&unsubscribe_action)
      AnonymousSubscription.new(&unsubscribe_action)
    end

    # Gets the subscription that does nothing when unsubscribed.
    def self.empty
      EmptySubscription.instance
    end
  end
end