+ = case resStatus res of
+ -- 1xx は body を持たない
+ -- 2xx の body は補完しない
+
+ -- 3xx
+ MovedPermanently
+ → txt ("The resource at " ⧺ path ⧺ " has been moved to ")
+ <+>
+ eelem "a" += sattr "href" loc
+ += txt loc
+ <+>
+ txt " permanently."
+
+ Found
+ → txt ("The resource at " ⧺ path ⧺ " is currently located at ")
+ <+>
+ eelem "a" += sattr "href" loc
+ += txt loc
+ <+>
+ txt ". This is not a permanent relocation."
+
+ SeeOther
+ → txt ("The resource at " ⧺ path ⧺ " can be found at ")
+ <+>
+ eelem "a" += sattr "href" loc
+ += txt loc
+ <+>
+ txt "."
+
+ TemporaryRedirect
+ → txt ("The resource at " ⧺ path ⧺ " is temporarily located at ")
+ <+>
+ eelem "a" += sattr "href" loc
+ += txt loc
+ <+>
+ txt "."
+
+ -- 4xx
+ BadRequest
+ → txt "The server could not understand the request you sent."
+
+ Unauthorized
+ → txt ("You need a valid authentication to access " ⧺ path)
+
+ Forbidden
+ → txt ("You don't have permission to access " ⧺ path)
+
+ NotFound
+ → txt ("The requested URL " ⧺ path ⧺ " was not found on this server.")
+
+ Gone
+ → txt ("The resource at " ⧺ path ⧺ " was here in past times, but has gone permanently.")
+
+ RequestEntityTooLarge
+ → txt ("The request entity you sent for " ⧺ path ⧺ " was too large to accept.")
+
+ RequestURITooLarge
+ → txt "The request URI you sent was too large to accept."
+
+ -- 5xx
+ InternalServerError
+ → txt ("An internal server error has occured during the process of your request to " ⧺ path)
+
+ ServiceUnavailable
+ → txt "The service is temporarily unavailable. Try later."
+
+ _ → none
+
+ where
+ path ∷ String
+ path = let uri = reqURI $ fromJust req
+ in
+ uriPath uri
+
+ loc ∷ String
+ loc = A.toString $ fromJust $ getHeader "Location" res