# encoding: utf-8
require "json"

module ServiceObjects

  # Describes messages published by service objects
  class Message
    include Comparable

    # @!attribute [r] type
    # The type of the message
    #
    # @return [String]
    attr_reader :type

    # @!attribute [r] text
    # The text of the message
    #
    # @return [String]
    attr_reader :text

    # @!attribute [r] priority
    # The priority level for the message
    #
    # If priority hasn't been set on initialization, sets it to -1.0 for errors,
    # or 0.0 otherwise.
    #
    # @return [Float]
    def priority
      return @custom_priority.to_f if @custom_priority
      type == "error" ? -1.0 : 0.0
    end

    # @!scope class
    # @!method new(type:, text:, priority:)
    # Constructs and freezes the message object
    #
    # @example
    #   Message.new type: "info", text: "foo", priority: 3
    #
    # @param [#to_s] type
    # @param [#to_s] text
    # @param [#to_f] priority
    #   optional custom priority of the message (the less the higher)
    #
    # @return [ServiceObjects::Message]
    #   the frozen message object
    def initialize(type:, text:, priority: nil)
      @type = type.to_s.freeze
      @text = text.to_s.freeze
      @custom_priority = priority
      freeze
    end

    # Checks equality of the message to the other object
    #
    # @param [Object] other
    #
    # @return [true]
    #   if messages has the same attributes
    # @return [false]
    #   if the other object is not a message or has different argument(s)
    def ==(other)
      (self <=> other) == 0
    end

    # Compares the message with the other object
    #
    # @param [Object] other
    #
    # @return [-1, 0, 1]
    #   if the argument is a message
    # @return [nil]
    #   if the other object is not a message
    def <=>(other)
      return unless other.is_a? self.class
      [:priority, :type, :text]
        .map { |key| __compare_to__ other, by: key }
        .detect { |value| value } || 0
    end

    # Converts the message object to hash
    #
    # @return [Hash]
    def to_h
      { type: type, text: text }
    end

    # Converts the message object to json
    #
    # @return [String]
    def to_json
      to_h.to_json
    end

    # A human-readable representation of the message
    #
    # @return [String]
    def inspect
      %W(
        #<ServiceObjects::Message:#{ object_id }
        type=\"#{ type }\"
        text=\"#{ text }\"
        priority=#{ priority }>
      ).join(" ")
    end

    private

    def __compare_to__(other, by:)
      value = (send(by) <=> other.send(by))
      value == 0 ? nil : value
    end

  end # class Message

end # module ServiceObjects