1 files changed, 158 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
new file mode 100644
index 0000000000..ea647e051a
--- /dev/null
+++ b/actionpack/lib/action_dispatch/journey/gtg/transition_table.rb
@@ -0,0 +1,158 @@
+# frozen_string_literal: true
+
+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)
+          return [] if t.empty?
+
+          regexps = []
+
+          t.map { |s|
+            if states = @regexp_states[s]
+              regexps.concat states.map { |re, v| re === a ? v : nil }
+            end
+
+            if states = @string_states[s]
+              states[a]
+            end
+          }.compact.concat regexps
+        end
+
+        def as_json(options = nil)
+          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
+
+          {
+            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 __dir__, "..", "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.sample(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 }.sample
+                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]
+
+          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.flat_map(&:values)
+          rs = @regexp_states.keys + @regexp_states.values.flat_map(&:values)
+          (ss + rs).uniq
+        end
+
+        def transitions
+          @string_states.flat_map { |from, hash|
+            hash.map { |s, to| [from, s, to] }
+          } + @regexp_states.flat_map { |from, hash|
+            hash.map { |s, to| [from, s, to] }
+          }
+        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
+      end
+    end
+  end
+end