module Lita
  # Adapters are the glue between Lita's API and a chat service.
  class Adapter
    # The instance of {Lita::Robot}.
    # @return [Lita::Robot]
    attr_reader :robot

    class << self
      # A list of configuration keys that are required for the adapter to boot.
      # @return [Array]
      attr_reader :required_configs

      # Defines configuration keys that are requried for the adapter to boot.
      # @param keys [String, Symbol] The required keys.
      # @return [void]
      def require_config(*keys)
        @required_configs ||= []
        @required_configs.concat(keys.flatten.map(&:to_sym))
      end

      alias_method :require_configs, :require_config
    end

    # @param robot [Lita::Robot] The currently running robot.
    def initialize(robot)
      @robot = robot
      ensure_required_configs
    end

    # @!method run
    # The main loop. Should connect to the chat service, listen for incoming
    # messages, create {Lita::Message} objects from them, and dispatch them to
    # the robot by calling {Lita::Robot#receive}.
    # @return [void]
    # @abstract This should be implemented by the adapter.

    # @!method send_messages(target, strings)
    # Sends one or more messages to a user or room.
    # @param target [Lita::Source] The user or room to send messages to.
    # @param strings [Array<String>] An array of messages to send.
    # @return [void]
    # @abstract This should be implemented by the adapter.

    # @!method set_topic(target, topic)
    # Sets the topic for a room.
    # @param target [Lita::Source] The room to change the topic for.
    # @param topic [String] The new topic.
    # @return [void]
    # @abstract This should be implemented by the adapter.

    # @!method shut_down
    # Performs any clean up necessary when disconnecting from the chat service.
    # @return [void]
    # @abstract This should be implemented by the adapter.
    [:run, :send_messages, :set_topic, :shut_down].each do |method|
      define_method(method) do |*args|
        Lita.logger.warn("This adapter has not implemented ##{method}.")
      end
    end

    private

    # Logs a fatal message and aborts if a required config key is not set.
    def ensure_required_configs
      required_configs = self.class.required_configs
      return if required_configs.nil?

      missing_keys = []

      required_configs.each do |key|
        missing_keys << key unless Lita.config.adapter[key]
      end

      unless missing_keys.empty?
        Lita.logger.fatal(
"The following keys are required on config.adapter: #{missing_keys.join(", ")}"
        )
        abort
      end
    end
  end
end