require_relative 'version'

class Minimus

  TransitionError = Class.new(StandardError)

  attr_reader :states, :initial_state
  attr_accessor :current_state

  def initialize(*states)
    @states = states
    @initial_state = states.first
    @current_state = initial_state
  end

  def move(new_state)
    return false unless move_possible?(new_state)
    self.current_state = new_state

    yield if block_given?
  end

  def move!(new_state)
    unless move_possible?(new_state)
      raise TransitionError, %Q{unallowed transition from
         #{current_state} to #{new_state}}
    end
    self.current_state = new_state

    yield if block_given?
  end

  private

  def move_possible?(new_state)
    states[states.index(current_state) + 1] == new_state
  end
end