WIP inheritance

nixite/html.nix

@@ -1,7 +1,9 @@
 let
   keyvalue = key: value:
     assert builtins.isString key;
-    if value == "" || value == [ ] || value == { } then
+    if builtins.isAttrs value then 
+      builtins.trace "Skipping ${key} as it is a set" "" else
+    if value == "" || value == [ ] then
       ""
     else
       ''${key}="${toString value}"'';
@@ -26,11 +28,27 @@ in rec {
         else
           keyvalue key value) attrs)));
 
-  tag = tag: attrs: child: {
-    inherit tag attrs child;
-    __toString = toHTML;
+  tag = tag: {
+    inherit tag;
+    __functor = self: attrs:
+      if !(builtins.isAttrs attrs) then
+        throw "HTML tag requires attribute set"
+      else {
+        inherit attrs;
+        __functor = self: child:
+          if !(isTag child) then
+            throw "tag child must be tag, list, or string"
+          else {
+            inherit tag attrs child;
+            __toString = toHTML;
+          };
+      };
   };
 
+  isTag = tag:
+    (builtins.isString tag || builtins.isList tag
+      || (tag ? toString && builtins.isFunction tag.toString));
+
   addToHead = page: heads:
     page // {
       child = map