module Parser::Lexer::Explanation

def self.included(klass)
  klass.class_exec do
    alias_method :state_before_explanation=,  :state=
    alias_method :advance_before_explanation, :advance
    remove_method :state=, :advance
  end
end

def advance
  type, (val, range) = advance_before_explanation
  more = "(in-kwarg)" if @context.in_kwarg
  puts decorate(range,
                Color.green("#{type} #{val.inspect}"),
                "#{state.to_s.ljust(12)} #{@cond} #{@cmdarg} #{more}")
  [ type, [val, range] ]
end

def decorate(range, token, info)
  from, to = range.begin.column, range.end.column
  line = range.source_line + '   '
  line[from...to] = Color.underline(line[from...to])
  tail_len   = to - from - 1
  tail       = '~' * (tail_len >= 0 ? tail_len : 0)
  decoration =  "#{" " * from}#{Color.red("^#{tail}", bold: true)} #{token} ".
                    ljust(68) + info
  [ line, decoration ]
end

def state=(new_state)
  puts "  #{Color.yellow(">>> STATE SET <<<", bold: true)} " +
       "#{new_state.to_s.ljust(12)} #{@cond} #{@cmdarg}".rjust(66)
  self.state_before_explanation = new_state
end