waiter_and_chef_command_pattern.rb

# frozen_string_literal: true

require 'ostruct'

# Command "Interface"
class Command
  attr_accessor :errors, :input, :output

  def initialize(**input)
    @errors = []
    @output = nil
    @input = OpenStruct.new(**input)
  end

  def execute
    raise NotImplementedError, "#{self.class} lacks '#{__method__}' method implementation"
  end

  def errors?
    @errors.any?
  end
end

# Receiver
class Chef
  def cook(order)
    raise 'we are running out of fishes' if order.to_s.casecmp('fish').zero?

    "Here's your #{order}"
  end
end

# Command used to cook fish
class CookFishCommand < Command
  def initialize(receiver)
    @receiver = receiver
    super(order: 'fish')
  end

  def execute
    @output = @receiver.cook(input.order)
  rescue StandardError => e
    errors << e
  end
end

# Command used to cook meat
class CookMeatCommand < Command
  def initialize(receiver)
    @receiver = receiver
    super(order: 'meat')
  end

  def execute
    @output = @receiver.cook(input.order)
  end
end

# Invoker
class Waiter
  def initialize
    @chef = Chef.new
    @menu = {
      fish: CookFishCommand,
      meat: CookMeatCommand
    }
  end

  def take_order(key)
    command_class = @menu[key]
    return "We don't have #{key} in our menu" if command_class.nil?

    command = command_class.new(@chef)
    command.execute

    # Here we deal with errors
    return "Sorry sir, but #{command.errors.join(', ')}" if command.errors?

    command.output
  end
end

waiter = Waiter.new

waiter.take_order(:meat) # Same as execute command
waiter.take_order(:fish) # Same as execute command