module Translate

  # doctest: Translate should give the pre method for a normal method
  #   >> Translate.method_pre(:method)
  #   => :method_pre
  #
  # doctest: Translate should give the pre method for a question method
  #   >> Translate.method_pre(:method?)
  #   => :method_pre?
  #
  # doctest: Translate should give the pre method for an exclamation method
  #   >> Translate.method_pre(:method!)
  #   => :method_pre!
  #
  # doctest: Translate should give the pre method for an assignment method
  #   >> Translate.method_pre(:method=)
  #   => :method_pre=
  #
  # doctest: Translate should give the pre method for an operator
  #   >> Translate.method_pre(:+)
  #   => :op_plus_pre
  def self.method_pre(method)
     method_with_suffix(method, :pre)
  end

  # doctest: Translate should give the post method for a normal method
  #   >> Translate.method_post(:method)
  #   => :method_post
  #
  # doctest: Translate should give the post method for a question method
  #   >> Translate.method_post(:method?)
  #   => :method_post?
  #
  # doctest: Translate should give the post method for an exclamation method
  #   >> Translate.method_post(:method!)
  #   => :method_post!
  #
  # doctest: Translate should give the post method for an assignment method
  #   >> Translate.method_post(:method=)
  #   => :method_post=
  #
  # doctest: Translate should give the post method for an operator
  #   >> Translate.method_post(:+)
  #   => :op_plus_post
  def self.method_post(method)
    method_with_suffix(method, :post)
  end

private

  def self.method_with_suffix(method, type)
    operator = OPERATOR[method]
    suffix = '_' + type.to_s
    if operator.nil?
      method_string = method.to_s
      length = method_string.length
      head = method_string[0...length-1]
      tail = method_string[length-1...length]
      if ['?', '!', '='].include?(tail)
        (head + suffix + tail).to_sym
      else
        (method_string + suffix).to_sym
      end
    else
      ('op_' + operator.to_s + suffix).to_sym
    end
  end

  OPERATOR = {
    :[]  => :element_read,
    :[]= => :element_write,
    :**  => :power,
    :~   => :not,
    :+@  => :unary_plus,
    :-@  => :unary_minus,
    :*   => :product,
    :/   => :quotient,
    :%   => :modulo,
    :+   => :plus,
    :-   => :minus,
    :>>  => :right_shift,
    :<<  => :left_shift,
    :&   => :and,
    :^   => :xor,
    :|   => :or,
    :<=  => :less_or_equal,
    :<   => :less,
    :>   => :greater,
    :>=  => :greater_or_equal,
    :<=> => :comparison,
    :==  => :eql,
    :=== => :case_comparison,
    :=~  => :match
  }

end