require 'strscan'

module ActionDispatch
  module Journey
    module NFA
      class MatchData
        attr_reader :memos

        def initialize memos
          @memos = memos
        end
      end

      class Simulator
        attr_reader :tt

        def initialize transition_table
          @tt = transition_table
        end

        def simulate string
          input = StringScanner.new string
          state = tt.eclosure 0
          until input.eos?
            sym   = input.scan(%r([/.?]|[^/.?]+))

            # FIXME: tt.eclosure is not needed for the GTG
            state = tt.eclosure tt.move(state, sym)
          end

          acceptance_states = state.find_all { |s|
            tt.accepting? tt.eclosure(s).sort.last
          }

          return if acceptance_states.empty?

          memos = acceptance_states.map { |x| tt.memo x }.flatten.compact

          MatchData.new memos
        end

        alias :=~    :simulate
        alias :match :simulate
      end
    end
  end
end