usage追加してみた。一文字で打てるようにはしてない！

text_game.rb

require 'yaml'
require 'hashie'
require 'readline'

@env = Hashie::Mash.new(YAML.load_file("./world.yml"))
@allowed_commands = %w(look walk pickup inventory)
@location = :living_room

def look
  res = []
  res << describe_location(@location)
  res << describe_paths(@location)
  res << describe_objects(@location)
  res.join("\n")
end

def describe_location(location)
  @env.node[location].desc
end

def describe_paths(location)
  @env.node[location].edges.map { |edge| 
    "there is a #{edge[:to]} going #{edge[:direction]} from here."
  }.join("\n")
end

def describe_objects(location)
  return unless objs = @env.objects[location]
  objs.map { |obj| "you see a #{obj} on the floor." }.join("\n")
end

def pickup(object)
  if @env.objects[@location].include?(object)
    @env.objects[@location].delete(object)
    @env.objects[:body].push(object)
    "you are now carrying the #{object}."
  else
    "you cannot get that."
  end
end

def inventory
  items = @env.objects[:body].join(", ")
  items = "none" if items.empty?
  "items: #{items}."
end

def walk(direction)
  if next_edge = @env.node[@location].edges.find { |edge| edge[:direction] == direction.to_sym }
    @location = next_edge[:to]
    look
  else
    "you cannot go that way."
  end
end

def usage
  @env.commands.map { |cmd, args|
    str = "[#{cmd[0]}]#{cmd[1..-1]}"
    args = args.map { |a| %Q(\"#{a}\") }.join(" ")
    str << " #{args}" unless args.empty?
    str
  }.join(", ")
end

loop do
  unless input = Readline.readline(">> ", true)
    puts "please enter any commands."
    puts usage
    next 
  end

  cmd, *args = input.chomp.split
  if cmd == "quit"
    puts "bye-bye!"
    break
  elsif @env.commands.keys.include?(cmd)
    cmd << args.map { |arg| " \"#{arg}\"" }.join
    puts eval(cmd)
  else
    puts "invalid command."
    puts usage
  end

  puts ""
end

world.yml

node:
  living_room:
    desc: "you are in the living-room. a wizard is snoring loudly on the couch."
    edges:
      - to:        :garden
        direction: :west
        via:       :door
      - to:        :attic
        direction: :upstairs
        via:       :door
  garden:
    desc: "you are ina beautiful garden. there is a well in front of you."
    edges:
      - to:        :living_room
        direction: :east
        via:       :door
  attic:
    desc: "you are in the attic. there is a giant welding torch in the corner."
    edges:
      - to:        :living_room
        direction: :downstairs
        via:       :ladder

objects:
  living_room: ["whiskey", "bucket"]
  garden:      ["frog", "chain"]
  body:        []

commands:
  look:      []
  walk:      ["direction"]
  pickup:    ["object"]
  inventory: []
  quit:      []

例外処理が無いね 👎

usageが欲しいのぅ