correct bbb link substitution

(unfortunately this one's hardcoded, the config options just aren't
general enough)

config.json

@@ -16,12 +16,6 @@
       "scope" : ["map"],
       "substs" : {
       }
-    },
-    "bbb" : {
-      "scope" : ["bbb"],
-      "allowed" : [],
-      "blocked" : [],
-      "prefix" : "https://bbb.rc3.world/"
     }
   }
 }

lib/Properties.hs

@@ -40,7 +40,7 @@ import           LintWriter    (LintWriter, adjust, askContext, askFileDepth,
 import           Paths         (PathResult (..), RelPath (..), getExtension,
                                 isOldStyle, parsePath)
 import           Types         (Dep (Link, Local, LocalMap, MapLink))
-import           Uris          (SubstError (..), applySubst)
+import           Uris          (SubstError (..), applySubst, parseUri)
 
 
 -- | Checks an entire map for "general" lints.
@@ -289,15 +289,16 @@ checkTileLayerProperty p@(Property name _value) = case name of
       isIntInRange 0 100 p
     "bbbRoom" -> do
       removeProperty "bbbRoom"
-      unwrapURI (Proxy @"bbb") p
-        (\link -> do
+      unwrapString p $ \str -> case parseUri str of
+        Just ("bbb",assembly_slug, room_slug)
+          | "/" `isPrefixOf` room_slug && T.length room_slug >= 2 -> do
+          let link = "https://rc3.world/assembly/"<>assembly_slug<>"/bbb"<>room_slug
           dependsOn (Link link)
           setProperty "openWebsite" link
           setProperty "silent" (BoolProp True)
           setProperty "openWebsitePolicy"
             ("fullscreen;camera;microphone;display-capture" :: Text)
-        )
-        (const $ complain "property \"bbbRoom\" cannot be used with local links.")
+        _ -> complain "the \"bbbRoom\" property must take a link of the form bbb://assembly_slug/room_slug."
     "bbbTrigger" -> do
       removeProperty "bbbTrigger"
       requireProperty "bbbRoom"