class ActionCable::SubscriptionAdapter::SubscriberMap

def add_channel(channel, on_success)
  on_success.call if on_success
end

def add_subscriber(channel, subscriber, on_success)
  @sync.synchronize do
    new_channel = !@subscribers.key?(channel)
    @subscribers[channel] << subscriber
    if new_channel
      add_channel channel, on_success
    elsif on_success
      on_success.call
    end
  end
end

def broadcast(channel, message)
  list = @sync.synchronize do
    return if !@subscribers.key?(channel)
    @subscribers[channel].dup
  end
  list.each do |subscriber|
    invoke_callback(subscriber, message)
  end
end

def initialize
  @subscribers = Hash.new { |h, k| h[k] = [] }
  @sync = Mutex.new
end

def invoke_callback(callback, message)
  callback.call message
end

def remove_channel(channel)
end

def remove_subscriber(channel, subscriber)
  @sync.synchronize do
    @subscribers[channel].delete(subscriber)
    if @subscribers[channel].empty?
      @subscribers.delete channel
      remove_channel channel
    end
  end
end