1 files changed, 71 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/journey/scanner.rb b/actionpack/lib/action_dispatch/journey/scanner.rb
new file mode 100644
index 0000000000..2a075862e9
--- /dev/null
+++ b/actionpack/lib/action_dispatch/journey/scanner.rb
@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+require "strscan"
+
+module ActionDispatch
+  module Journey # :nodoc:
+    class Scanner # :nodoc:
+      def initialize
+        @ss = nil
+      end
+
+      def scan_setup(str)
+        @ss = StringScanner.new(str)
+      end
+
+      def eos?
+        @ss.eos?
+      end
+
+      def pos
+        @ss.pos
+      end
+
+      def pre_match
+        @ss.pre_match
+      end
+
+      def next_token
+        return if @ss.eos?
+
+        until token = scan || @ss.eos?; end
+        token
+      end
+
+      private
+
+        # takes advantage of String @- deduping capabilities in Ruby 2.5 upwards
+        # see: https://bugs.ruby-lang.org/issues/13077
+        def dedup_scan(regex)
+          r = @ss.scan(regex)
+          r ? -r : nil
+        end
+
+        def scan
+          case
+            # /
+          when @ss.skip(/\//)
+            [:SLASH, "/"]
+          when @ss.skip(/\(/)
+            [:LPAREN, "("]
+          when @ss.skip(/\)/)
+            [:RPAREN, ")"]
+          when @ss.skip(/\|/)
+            [:OR, "|"]
+          when @ss.skip(/\./)
+            [:DOT, "."]
+          when text = dedup_scan(/:\w+/)
+            [:SYMBOL, text]
+          when text = dedup_scan(/\*\w+/)
+            [:STAR, text]
+          when text = @ss.scan(/(?:[\w%\-~!$&'*+,;=@]|\\[:()])+/)
+            text.tr! "\\", ""
+            [:LITERAL, -text]
+            # any char
+          when text = dedup_scan(/./)
+            [:LITERAL, text]
+          end
+        end
+    end
+  end
+end