module Duplo

# File lib/duplo.rb, line 22
def add(toy, part)
  case toy
  when Array, Set
    toy << part
  when Hash
    toy.store(toy.size, part)
  end
end

# File lib/duplo.rb, line 35
def build(part, path = [], &block)
  raise %(Don't know how to build "#{part}", sorry) unless can_build? part

  part = part.dup
  brick = part.slice! BRICK
  type, size = crack brick
  toy = type.new

  if part.empty?
    block ||= proc { |path| path.is_a?(Array) ? path.last : path }
    size.times { |i| add toy, block.call(path.empty? ? i : path + [i]) }
  else
    size.times { |i| add toy, build(part, path + [i], &block) }
  end

  toy
end

# File lib/duplo.rb, line 31
def can_build?(toy)
  !!(toy.strip =~ /\A#{BRICK}+\z/)
end

# File lib/duplo.rb, line 57
def crack(brick)
  type, size = brick.split("", 2)
  size = size.empty? ? default_size : size.to_i
  [TOYS[type], size]
end

# File lib/duplo.rb, line 18
def default_size
  @default_size || 5
end

# File lib/duplo.rb, line 53
def smash(toy)
  toy.scan(BRICK).map { |brick| crack brick }
end

# File lib/duplo.rb, line 63
def spell(toy)
  smash(toy).map.with_index do |(type, size), idx|
    plural = idx == 0 ? "" : type == Hash ? "es" : "s"
    size.zero? ? "empty #{type}#{plural}" : "#{size}-element #{type}#{plural}"
  end.join(" containing ")
end

# File lib/duplo.rb, line 78
def method_missing(method_name, *arguments, &block)
  toy = method_name.to_s
  if Duplo.can_build? toy
    Duplo.build toy, *arguments, &block
  else
    super
  end
end

# File lib/duplo.rb, line 73
def respond_to_missing?(method_name, *)
  toy = method_name.to_s
  Duplo.can_build?(toy) || super
end