result.rb

# frozen_string_literal: true

module Nanites
  # Command result
  class Result
    # Defines result status constants
    module States
      UNKNOWN = Option.maybe
      SUCCESS = Option.some true
      ERROR = Option.none

      class << self
        # Is given code a valid status code?
        # @return [Boolean]
        def valid_status?(code)
          constants(false).each do |constant|
            return true if States.const_get(constant).eql?(code)
          end

          false
        end
      end
    end

    attr_reader :messages, :option, :status

    # @param [Object] option
    # @param [States] status
    def initialize(option, status = States::UNKNOWN, *messages)
      raise ArgumentError, 'Payload must be an "Option"' unless option.is_a?(Nanites::Option)
      raise ArgumentError, "Unknown status code '#{status}'" unless States.valid_status?(status)

      @option = option
      @messages = messages
      @status = status
    end

    # Does the result indicate some error?
    def error?
      @status.eql? States::ERROR
    end

    # Does the result indicate successful command execution?
    def success?
      @status.eql? States::SUCCESS
    end

    # Does the result indicate unknown command execution?
    def unknown?
      @status.eql?(States::UNKNOWN) || (!error? && !success?)
    end

    class << self
      # Create result object indicating an erroneous command execution
      # @param [Object] value optional payload
      # @param [Array] messages optional informational messages
      # @return [Nanites::Result]
      def error(value, *messages)
        Result.new option_for_payload(value), States::ERROR, *messages
      end

      # Create successful result object
      # @param [Object] value optional payload
      # @param [Array] messages optional informational messages
      # @return [Nanites::Result]
      def success(value, *messages)
        Result.new option_for_payload(value), States::SUCCESS, *messages
      end

      # Create unknown result
      # @return [Nanites::Result]
      def unknown
        Result.new Option.none, States::UNKNOWN, 'Undefined result'
      end

      private

      # Helper returning an [Option] containing the actual payload
      # @param [Object] value The value to be wrapped
      # @return [Option]
      def option_for_payload(value)
        value ? Option.some(value) : Option.none
      end
    end
  end
end