wip

src/web/web-dom/node.h

@@ -55,6 +55,12 @@ struct Node :
         return *_parent;
     }
 
+    Node const &parentNode() const {
+        if (not _parent)
+            panic("node has no parent");
+        return *_parent;
+    }
+
     usize _parentIndex() {
         return indexOf(parentNode()._children, *this).unwrap();
     }

src/web/web-select/match.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include <web-dom/element.h>
+
+#include "select2.h"
+
+namespace Web::Select {
+
+// 17. Calculating a selector’s specificity
+// https://www.w3.org/TR/selectors-4/#specificity-rules
+struct Spec {
+    bool match;
+    isize a, b, c;
+
+    static Spec NOMATCH;
+    static Spec MATCH;
+
+    Spec operator and(Spec const &other) const {
+        return Spec{
+            match && other.match,
+            a + other.a,
+            b + other.b,
+            c + other.c
+        };
+    }
+
+    Spec operator or(Spec const &other) const {
+        return Spec{
+            match || other.match,
+            a + other.a,
+            b + other.b,
+            c + other.c
+        };
+    }
+};
+
+Spec match(Selector const &sel, Dom::Element &el) {
+    return sel.visit(Visitor{
+        [&](Combinator const &s) -> Spec {
+            switch (s.type) {
+            case Combinator::LIST:
+                return match(*s.lhs, el) or match(*s.rhs, el);
+
+            case Combinator::DESCENDANT:
+                return match(*s.lhs, el) or el.parentNode().map([&](auto &parent) {
+                    return match(*s.rhs, parent);
+                }).value_or(Spec::NOMATCH);
+
+            default:
+                return Spec::NOMATCH;
+            }
+        },
+        [&](auto &) -> Spec {
+            return Spec::NOMATCH;
+        }
+    });
+}
+
+} // namespace Web::Select