class ActiveSupport::Notifications::Fanout

def finish(name, id, payload, listeners = listeners_for(name))
  iterate_guarding_exceptions(listeners) { |s| s.finish(name, id, payload) }
end

def initialize
  @string_subscribers = Hash.new { |h, k| h[k] = [] }
  @other_subscribers = []
  @listeners_for = Concurrent::Map.new
  super
end

def iterate_guarding_exceptions(listeners)
  exceptions = nil
  listeners.each do |s|
    yield s
  rescue Exception => e
    exceptions ||= []
    exceptions << e
  end
  if exceptions
    if exceptions.size == 1
      raise exceptions.first
    else
      raise InstrumentationSubscriberError.new(exceptions), cause: exceptions.first
    end
  end
  listeners
end

def listeners_for(name)
  # this is correctly done double-checked locking (Concurrent::Map's lookups have volatile semantics)
  @listeners_for[name] || synchronize do
    # use synchronisation when accessing @subscribers
    @listeners_for[name] ||=
      @string_subscribers[name] + @other_subscribers.select { |s| s.subscribed_to?(name) }
  end
end

def listening?(name)
  listeners_for(name).any?
end

def publish(name, *args)
  iterate_guarding_exceptions(listeners_for(name)) { |s| s.publish(name, *args) }
end

def publish_event(event)
  iterate_guarding_exceptions(listeners_for(event.name)) { |s| s.publish_event(event) }
end

def start(name, id, payload)
  iterate_guarding_exceptions(listeners_for(name)) { |s| s.start(name, id, payload) }
end

def subscribe(pattern = nil, callable = nil, monotonic: false, &block)
  subscriber = Subscribers.new(pattern, callable || block, monotonic)
  synchronize do
    case pattern
    when String
      @string_subscribers[pattern] << subscriber
      @listeners_for.delete(pattern)
    when NilClass, Regexp
      @other_subscribers << subscriber
      @listeners_for.clear
    else
      raise ArgumentError,  "pattern must be specified as a String, Regexp or empty"
    end
  end
  subscriber
end

def unsubscribe(subscriber_or_name)
  synchronize do
    case subscriber_or_name
    when String
      @string_subscribers[subscriber_or_name].clear
      @listeners_for.delete(subscriber_or_name)
      @other_subscribers.each { |sub| sub.unsubscribe!(subscriber_or_name) }
    else
      pattern = subscriber_or_name.try(:pattern)
      if String === pattern
        @string_subscribers[pattern].delete(subscriber_or_name)
        @listeners_for.delete(pattern)
      else
        @other_subscribers.delete(subscriber_or_name)
        @listeners_for.clear
      end
    end
  end
end

def wait
end