class ActionDispatch::Journey::GTG::Builder

def transition_table
  dtrans   = TransitionTable.new
  marked   = {}.compare_by_identity
  state_id = Hash.new { |h, k| h[k] = h.length }.compare_by_identity
  dstates  = [firstpos(root)]
  until dstates.empty?
    s = dstates.shift
    next if marked[s]
    marked[s] = true # mark s
    s.group_by { |state| symbol(state) }.each do |sym, ps|
      u = ps.flat_map { |l| @followpos[l] }.uniq
      next if u.empty?
      from = state_id[s]
      if u.all? { |pos| pos == DUMMY_END_NODE }
        to = state_id[Object.new]
        dtrans[from, to] = sym
        dtrans.add_accepting(to)
        ps.each { |state| dtrans.add_memo(to, state.memo) }
      else
        to = state_id[u]
        dtrans[from, to] = sym
        if u.include?(DUMMY_END_NODE)
          ps.each do |state|
            if @followpos[state].include?(DUMMY_END_NODE)
              dtrans.add_memo(to, state.memo)
            end
          end
          dtrans.add_accepting(to)
        end
      end
      dstates << u
    end
  end
  dtrans
end