1 files changed, 189 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/journey/visitors.rb b/actionpack/lib/action_dispatch/journey/visitors.rb
new file mode 100644
index 0000000000..46bd58c178
--- /dev/null
+++ b/actionpack/lib/action_dispatch/journey/visitors.rb
@@ -0,0 +1,189 @@
+# encoding: utf-8
+module ActionDispatch
+  module Journey # :nodoc:
+    module Visitors # :nodoc:
+      class Visitor # :nodoc:
+        DISPATCH_CACHE = Hash.new { |h,k|
+          h[k] = "visit_#{k}"
+        }
+
+        def accept(node)
+          visit(node)
+        end
+
+        private
+
+          def visit node
+            send(DISPATCH_CACHE[node.type], node)
+          end
+
+          def binary(node)
+            visit(node.left)
+            visit(node.right)
+          end
+          def visit_CAT(n); binary(n); end
+
+          def nary(node)
+            node.children.each { |c| visit(c) }
+          end
+          def visit_OR(n); nary(n); end
+
+          def unary(node)
+            visit(node.left)
+          end
+          def visit_GROUP(n); unary(n); end
+          def visit_STAR(n); unary(n); end
+
+          def terminal(node); end
+          %w{ LITERAL SYMBOL SLASH DOT }.each do |t|
+            class_eval %{ def visit_#{t}(n); terminal(n); end }, __FILE__, __LINE__
+          end
+      end
+
+      # Loop through the requirements AST
+      class Each < Visitor # :nodoc:
+        attr_reader :block
+
+        def initialize(block)
+          @block = block
+        end
+
+        def visit(node)
+          super
+          block.call(node)
+        end
+      end
+
+      class String < Visitor # :nodoc:
+        private
+
+        def binary(node)
+          [visit(node.left), visit(node.right)].join
+        end
+
+        def nary(node)
+          node.children.map { |c| visit(c) }.join '|'
+        end
+
+        def terminal(node)
+          node.left
+        end
+
+        def visit_GROUP(node)
+          "(#{visit(node.left)})"
+        end
+      end
+
+      # Used for formatting urls (url_for)
+      class Formatter < Visitor # :nodoc:
+        attr_reader :options, :consumed
+
+        def initialize(options)
+          @options  = options
+          @consumed = {}
+        end
+
+        private
+
+          def visit_GROUP(node)
+            if consumed == options
+              nil
+            else
+              route = visit(node.left)
+              route.include?("\0") ? nil : route
+            end
+          end
+
+          def terminal(node)
+            node.left
+          end
+
+          def binary(node)
+            [visit(node.left), visit(node.right)].join
+          end
+
+          def nary(node)
+            node.children.map { |c| visit(c) }.join
+          end
+
+          def visit_SYMBOL(node)
+            key = node.to_sym
+
+            if value = options[key]
+              consumed[key] = value
+              Router::Utils.escape_path(value)
+            else
+              "\0"
+            end
+          end
+      end
+
+      class Dot < Visitor # :nodoc:
+        def initialize
+          @nodes = []
+          @edges = []
+        end
+
+        def accept(node)
+          super
+          <<-eodot
+  digraph parse_tree {
+    size="8,5"
+    node [shape = none];
+    edge [dir = none];
+    #{@nodes.join "\n"}
+    #{@edges.join("\n")}
+  }
+          eodot
+        end
+
+        private
+
+          def binary(node)
+            node.children.each do |c|
+              @edges << "#{node.object_id} -> #{c.object_id};"
+            end
+            super
+          end
+
+          def nary(node)
+            node.children.each do |c|
+              @edges << "#{node.object_id} -> #{c.object_id};"
+            end
+            super
+          end
+
+          def unary(node)
+            @edges << "#{node.object_id} -> #{node.left.object_id};"
+            super
+          end
+
+          def visit_GROUP(node)
+            @nodes << "#{node.object_id} [label=\"()\"];"
+            super
+          end
+
+          def visit_CAT(node)
+            @nodes << "#{node.object_id} [label=\"○\"];"
+            super
+          end
+
+          def visit_STAR(node)
+            @nodes << "#{node.object_id} [label=\"*\"];"
+            super
+          end
+
+          def visit_OR(node)
+            @nodes << "#{node.object_id} [label=\"|\"];"
+            super
+          end
+
+          def terminal(node)
+            value = node.left
+
+            @nodes << "#{node.object_id} [label=\"#{value}\"];"
+          end
+      end
+    end
+  end
+end