class ActionCable::SubscriptionAdapter::Redis::Listener

def add_channel(channel, on_success)
  @subscription_lock.synchronize do
    ensure_listener_running
    @subscribe_callbacks[channel] << on_success
    when_connected { send_command("subscribe", channel) }
  end
end

def ensure_listener_running
  @thread ||= Thread.new do
    Thread.current.abort_on_exception = true
    conn = @adapter.redis_connection_for_subscriptions
    listen conn
  end
end

def initialize(adapter, event_loop)
  super()
  @adapter = adapter
  @event_loop = event_loop
  @subscribe_callbacks = Hash.new { |h, k| h[k] = [] }
  @subscription_lock = Mutex.new
  @raw_client = nil
  @when_connected = []
  @thread = nil
end

def invoke_callback(*)
  @event_loop.post { super }
end

def listen(conn)
  conn.without_reconnect do
    original_client = conn.client
    conn.subscribe("_action_cable_internal") do |on|
      on.subscribe do |chan, count|
        @subscription_lock.synchronize do
          if count == 1
            @raw_client = original_client
            until @when_connected.empty?
              @when_connected.shift.call
            end
          end
          if callbacks = @subscribe_callbacks[chan]
            next_callback = callbacks.shift
            @event_loop.post(&next_callback) if next_callback
            @subscribe_callbacks.delete(chan) if callbacks.empty?
          end
        end
      end
      on.message do |chan, message|
        broadcast(chan, message)
      end
      on.unsubscribe do |chan, count|
        if count == 0
          @subscription_lock.synchronize do
            @raw_client = nil
          end
        end
      end
    end
  end
end

def remove_channel(channel)
  @subscription_lock.synchronize do
    when_connected { send_command("unsubscribe", channel) }
  end
end

def send_command(*command)
  @raw_client.write(command)
  very_raw_connection =
    @raw_client.connection.instance_variable_defined?(:@connection) &&
    @raw_client.connection.instance_variable_get(:@connection)
  if very_raw_connection && very_raw_connection.respond_to?(:flush)
    very_raw_connection.flush
  end
end

def shutdown
  @subscription_lock.synchronize do
    return if @thread.nil?
    when_connected do
      send_command("unsubscribe")
      @raw_client = nil
    end
  end
  Thread.pass while @thread.alive?
end

def when_connected(&block)
  if @raw_client
    block.call
  else
    @when_connected << block
  end
end