01

# customer order a burger

class Order
  def burger
    raise NotImplementedError
  end
end

class Cook < Order
  def burger
    puts "make a buger"
  end
end

class Waitress
  attr_reader :cook

  def initialize(cook)
    @cook = cook
  end

  def place_order
    @cook.burger
  end
end

class Customer
  attr_reader :waitress

  def initialize(waitress)
    @waitress = waitress
  end

  def order_a_burger
    @waitress.place_order
  end
end

cook = Cook.new
waitress = Waitress.new(cook)
customer = Customer.new(waitress)
customer.order_a_burger

02.rb

# Command Interface
class Command
  def execute
    raise NotImplementedError
  end
end

class Light
  def on
    puts "light is on"
  end

  def off
    puts "light is off"
  end
end

class LightOnCommand < Command
  attr_reader :light

  def initialize(light)
    @light = light
  end

  def execute
    @light.on
  end
end

class SimpleRemoteControl
  attr_reader :slot

  def initialize(slot)
    @slot = slot
  end

  def button_was_pressed
    @slot.execute
  end
end

light = Light.new
light_on = LightOnCommand.new(light)
remote = SimpleRemoteControl.new(light_on)
remote.button_was_pressed

undo.rb

# Command Interface
class Command
  def execute
    raise NotImplementedError
  end

  def undo
    raise NotImplementedError
  end
end

class Light
  attr_reader :location

  def initialize(location)
    @location = location
  end

  def on
    puts "#{@location} light is on"
  end

  def off
    puts "#{@location} light is off"
  end
end

class LightOnCommand < Command
  attr_reader :light

  def initialize(light)
    @light = light
  end

  def execute
    @light.on
  end

  def undo
    @light.off
  end
end

class LightOffCommand < Command
  attr_reader :light

  def initialize(light)
    @light = light
  end

  def execute
    @light.off
  end

  def undo
    @light.on
  end
end

class Stereo
  attr_reader :location

  def initialize(location)
    @location = location
  end

  def on
    puts "#{@location} stereo is on"
  end

  def off
    puts "#{@location} stereo is off"
  end

  def set_cd
    puts "#{@location} stereo is set for CD input"
  end

  def set_dvd
    puts "#{@location} stereo is set for DVD input"
  end

  def set_radio
    puts "#{@location} stereo is set for Radio"
  end

  def set_volume(volume)
    puts "#{@location} stereo volume set to #{volume}"
  end
end

class StereoOnWithCDCommand < Command
  attr_reader :stereo

  def initialize(stereo)
    @stereo = stereo
  end

  def execute
    @stereo.on
    @stereo.set_cd
    @stereo.set_volume(11)
  end
end

class StereotOffCommand < Command
  attr_reader :stereo

  def initialize(stereo)
    @stereo = stereo
  end

  def execute
    @stereo.off
  end
end

class CeilingFan
  attr_reader :location
  attr_reader :level
  HIGH = 2
  MEDIUM = 1
  LOW = 0

  def initialize(location)
    @level = HIGH
    @location = location
  end

  def high
    @level = HIGH
    puts "#{@location} ceiling fan is on high"
  end

  def medium
    @level = MEDIUM
    puts "#{@location} ceiling fan is on medium"
  end

  def low
    @level = LOW
    puts "#{@location} ceiling fan is on low"
  end

  def off
    puts "#{@location} ceiling fan is off"
  end

  def speed
    @level
  end
end

class CeilingFanOnCommand < Command
  attr_reader :ceiling_fan

  def initialize(ceiling_fan)
    @ceiling_fan = ceiling_fan
  end

  def execute
    @ceiling_fan.high
  end
end

class CeilingFanOffCommand < Command
  attr_reader :ceiling_fan

  def initialize(ceiling_fan)
    @ceiling_fan = ceiling_fan
  end

  def execute
    @ceiling_fan.off
  end
end

class SimpleRemoteControl
  attr_reader :slot

  def initialize(slot)
    @slot = slot
  end

  def button_was_pressed
    @slot.execute
  end
end

class RemoteControl
  attr_reader :on_commands
  attr_reader :off_commands
  attr_reader :undo_command

  def initialize
    @on_commands = Array.new
    @off_commands = Array.new
  end

  def set_command(on_command, off_command)
    @on_commands << on_command
    @off_commands << off_command
  end

  def on_button_was_pushed(index)
    @on_commands[index].execute
    @undo_command = @on_commands[index]
  end

  def off_button_was_pushed(index)
    @off_commands[index].execute
    @undo_command = @off_commands[index]
  end

  def undo_button_was_pushed
    @undo_command.undo
  end
end

living_room_light = Light.new("living room")
living_room_light_on = LightOnCommand.new(living_room_light)
living_room_light_off = LightOffCommand.new(living_room_light)

remote = RemoteControl.new
remote.set_command(living_room_light_on, living_room_light_off)

remote.on_button_was_pushed(0)
remote.off_button_was_pushed(0)
remote.undo_button_was_pushed