added missing Route file

src/Route.hs

@@ -0,0 +1,49 @@
+module Route (Route(..), link, breadcrumb) where
+
+import Common
+import Lucid
+import Data.List (foldl')
+
+data Route
+    = IndexRoute
+    | VisualRoute
+    | PostRoute
+    | ProjectsRoute
+    | ProjectRoute Text
+    | ProjectPageRoute Text Route
+    | VEntryRoute
+
+link :: Route -> Html ()
+link route = a_ [href_ (path route)] (toHtml $ name route)
+    where
+        path IndexRoute             = "/"
+        path ProjectsRoute          = "/projects.html"
+        path VisualRoute            = "/visual.html"
+        path PostRoute              = "/"
+        path (ProjectRoute _)       = "/projects/"
+        path (ProjectPageRoute _ _) = "/"
+        path VEntryRoute            = "/"
+
+        name IndexRoute             = "index"
+        name ProjectsRoute          = "projects"
+        name VisualRoute            = "visual"
+        name PostRoute              = "post"
+        name (ProjectRoute n)       = n
+        name (ProjectPageRoute n r) = n
+
+walk :: Route -> [Route]
+walk IndexRoute             = []
+walk VisualRoute            = []
+walk PostRoute              = [IndexRoute]
+walk ProjectsRoute          = []
+walk (ProjectRoute _)       = [ProjectsRoute]
+walk (ProjectPageRoute _ r) = walk r ++ [r]
+walk (VEntryRoute)          = [VisualRoute]
+
+breadcrumb :: Route -> Html ()
+breadcrumb route =
+    case walk route of
+        [] -> mempty
+        xs -> p_ [class_ "breadcrumb"] $
+                  foldl' (\b r -> b <> sep <> link r) "∅" xs
+    where sep = span_ [class_ "sep"] "←"