transition_table.rb

require 'action_dispatch/journey/nfa/dot'

module ActionDispatch
  module Journey # :nodoc:
    module GTG # :nodoc:
      class TransitionTable # :nodoc:
        include Journey::NFA::Dot

        attr_reader :memos

        def initialize
          @regexp_states = {}
          @string_states = {}
          @accepting     = {}
          @memos         = Hash.new { |h,k| h[k] = [] }
        end

        def add_accepting(state)
          @accepting[state] = true
        end

        def accepting_states
          @accepting.keys
        end

        def accepting?(state)
          @accepting[state]
        end

        def add_memo(idx, memo)
          @memos[idx] << memo
        end

        def memo(idx)
          @memos[idx]
        end

        def eclosure(t)
          Array(t)
        end

        def move(t, a)
          move_string(t, a).concat(move_regexp(t, a))
        end

        def to_json
          require 'json'

          simple_regexp = Hash.new { |h,k| h[k] = {} }

          @regexp_states.each do |from, hash|
            hash.each do |re, to|
              simple_regexp[from][re.source] = to
            end
          end

          JSON.dump({
            regexp_states: simple_regexp,
            string_states: @string_states,
            accepting:     @accepting
          })
        end

        def to_svg
          svg = IO.popen('dot -Tsvg', 'w+') { |f|
            f.write(to_dot)
            f.close_write
            f.readlines
          }
          3.times { svg.shift }
          svg.join.sub(/width="[^"]*"/, '').sub(/height="[^"]*"/, '')
        end

        def visualizer(paths, title = 'FSM')
          viz_dir   = File.join File.dirname(__FILE__), '..', 'visualizer'
          fsm_js    = File.read File.join(viz_dir, 'fsm.js')
          fsm_css   = File.read File.join(viz_dir, 'fsm.css')
          erb       = File.read File.join(viz_dir, 'index.html.erb')
          states    = "function tt() { return #{to_json}; }"

          fun_routes = paths.shuffle.first(3).map do |ast|
            ast.map { |n|
              case n
              when Nodes::Symbol
                case n.left
                when ':id' then rand(100).to_s
                when ':format' then %w{ xml json }.shuffle.first
                else
                  'omg'
                end
              when Nodes::Terminal then n.symbol
              else
                nil
              end
            }.compact.join
          end

          stylesheets = [fsm_css]
          svg         = to_svg
          javascripts = [states, fsm_js]

          # Annoying hack for 1.9 warnings
          fun_routes  = fun_routes
          stylesheets = stylesheets
          svg         = svg
          javascripts = javascripts

          require 'erb'
          template = ERB.new erb
          template.result(binding)
        end

        def []=(from, to, sym)
          to_mappings = states_hash_for(sym)[from] ||= {}
          to_mappings[sym] = to
        end

        def states
          ss = @string_states.keys + @string_states.values.map(&:values).flatten
          rs = @regexp_states.keys + @regexp_states.values.map(&:values).flatten
          (ss + rs).uniq
        end

        def transitions
          @string_states.map { |from, hash|
            hash.map { |s, to| [from, s, to] }
          }.flatten(1) + @regexp_states.map { |from, hash|
            hash.map { |s, to| [from, s, to] }
          }.flatten(1)
        end

        private

          def states_hash_for(sym)
            case sym
            when String
              @string_states
            when Regexp
              @regexp_states
            else
              raise ArgumentError, 'unknown symbol: %s' % sym.class
            end
          end

          def move_regexp(t, a)
            return [] if t.empty?

            t.map { |s|
              if states = @regexp_states[s]
                states.map { |re, v| re === a ? v : nil }
              end
            }.flatten.compact.uniq
          end

          def move_string(t, a)
            return [] if t.empty?

            t.map do |s|
              if states = @string_states[s]
                states[a]
              end
            end.compact
          end
      end
    end
  end
end