1 files changed, 198 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/journey/path/pattern.rb b/actionpack/lib/action_dispatch/journey/path/pattern.rb
new file mode 100644
index 0000000000..64b48ca45f
--- /dev/null
+++ b/actionpack/lib/action_dispatch/journey/path/pattern.rb
@@ -0,0 +1,198 @@
+require 'action_dispatch/journey/router/strexp'
+
+module ActionDispatch
+  module Journey # :nodoc:
+    module Path # :nodoc:
+      class Pattern # :nodoc:
+        attr_reader :spec, :requirements, :anchored
+
+        def self.from_string string
+          new Journey::Router::Strexp.build(string, {}, ["/.?"], true)
+        end
+
+        def initialize(strexp)
+          @spec         = strexp.ast
+          @requirements = strexp.requirements
+          @separators   = strexp.separators.join
+          @anchored     = strexp.anchor
+
+          @names          = nil
+          @optional_names = nil
+          @required_names = nil
+          @re             = nil
+          @offsets        = nil
+        end
+
+        def build_formatter
+          Visitors::FormatBuilder.new.accept(spec)
+        end
+
+        def ast
+          @spec.grep(Nodes::Symbol).each do |node|
+            re = @requirements[node.to_sym]
+            node.regexp = re if re
+          end
+
+          @spec.grep(Nodes::Star).each do |node|
+            node = node.left
+            node.regexp = @requirements[node.to_sym] || /(.+)/
+          end
+
+          @spec
+        end
+
+        def names
+          @names ||= spec.grep(Nodes::Symbol).map(&:name)
+        end
+
+        def required_names
+          @required_names ||= names - optional_names
+        end
+
+        def optional_names
+          @optional_names ||= spec.grep(Nodes::Group).flat_map { |group|
+            group.grep(Nodes::Symbol)
+          }.map(&:name).uniq
+        end
+
+        class RegexpOffsets < Journey::Visitors::Visitor # :nodoc:
+          attr_reader :offsets
+
+          def initialize(matchers)
+            @matchers      = matchers
+            @capture_count = [0]
+          end
+
+          def visit(node)
+            super
+            @capture_count
+          end
+
+          def visit_SYMBOL(node)
+            node = node.to_sym
+
+            if @matchers.key?(node)
+              re = /#{@matchers[node]}|/
+              @capture_count.push((re.match('').length - 1) + (@capture_count.last || 0))
+            else
+              @capture_count << (@capture_count.last || 0)
+            end
+          end
+        end
+
+        class AnchoredRegexp < Journey::Visitors::Visitor # :nodoc:
+          def initialize(separator, matchers)
+            @separator = separator
+            @matchers  = matchers
+            @separator_re = "([^#{separator}]+)"
+            super()
+          end
+
+          def accept(node)
+            %r{\A#{visit node}\Z}
+          end
+
+          def visit_CAT(node)
+            [visit(node.left), visit(node.right)].join
+          end
+
+          def visit_SYMBOL(node)
+            node = node.to_sym
+
+            return @separator_re unless @matchers.key?(node)
+
+            re = @matchers[node]
+            "(#{re})"
+          end
+
+          def visit_GROUP(node)
+            "(?:#{visit node.left})?"
+          end
+
+          def visit_LITERAL(node)
+            Regexp.escape(node.left)
+          end
+          alias :visit_DOT :visit_LITERAL
+
+          def visit_SLASH(node)
+            node.left
+          end
+
+          def visit_STAR(node)
+            re = @matchers[node.left.to_sym] || '.+'
+            "(#{re})"
+          end
+
+          def visit_OR(node)
+            children = node.children.map { |n| visit n }
+            "(?:#{children.join(?|)})"
+          end
+        end
+
+        class UnanchoredRegexp < AnchoredRegexp # :nodoc:
+          def accept(node)
+            %r{\A#{visit node}}
+          end
+        end
+
+        class MatchData # :nodoc:
+          attr_reader :names
+
+          def initialize(names, offsets, match)
+            @names   = names
+            @offsets = offsets
+            @match   = match
+          end
+
+          def captures
+            (length - 1).times.map { |i| self[i + 1] }
+          end
+
+          def [](x)
+            idx = @offsets[x - 1] + x
+            @match[idx]
+          end
+
+          def length
+            @offsets.length
+          end
+
+          def post_match
+            @match.post_match
+          end
+
+          def to_s
+            @match.to_s
+          end
+        end
+
+        def match(other)
+          return unless match = to_regexp.match(other)
+          MatchData.new(names, offsets, match)
+        end
+        alias :=~ :match
+
+        def source
+          to_regexp.source
+        end
+
+        def to_regexp
+          @re ||= regexp_visitor.new(@separators, @requirements).accept spec
+        end
+
+        private
+
+          def regexp_visitor
+            @anchored ? AnchoredRegexp : UnanchoredRegexp
+          end
+
+          def offsets
+            return @offsets if @offsets
+
+            viz = RegexpOffsets.new(@requirements)
+            @offsets = viz.accept(spec)
+          end
+      end
+    end
+  end
+end