Phase 4.2: Add query_index() and use it in matching_rules()

src/interpreter/style.rs

@@ -541,6 +541,62 @@ impl StyleSheet {
         self.index.is_some()
     }
 
+    pub fn query_index<'a>(
+        &'a self,
+        type_name: &str,
+        el_id: Option<&str>,
+        el_classes: &[&str],
+        active_pseudo: &[&str],
+        structural: &StructuralContext,
+        ancestors: &[AncestorInfo],
+        preceding_siblings: &[AncestorInfo],
+        el_attributes: &HashMap<String, String>,
+    ) -> Option<Vec<&'a HashMap<String, String>>> {
+        let index = self.index.as_ref()?;
+
+        let mut candidates: HashSet<RuleId> = HashSet::with_capacity(32);
+
+        candidates.extend(&index.universal_rules);
+
+        if let Some(rules) = index.by_tag.get(type_name) {
+            candidates.extend(rules);
+        }
+
+        for cls in el_classes {
+            if let Some(rules) = index.by_class.get(*cls) {
+                candidates.extend(rules);
+            }
+        }
+
+        if let Some(id) = el_id {
+            if let Some(rules) = index.by_id.get(id) {
+                candidates.extend(rules);
+            }
+        }
+
+        for (_, rule_id) in &index.complex_rules {
+            candidates.insert(*rule_id);
+        }
+
+        let mut matched: Vec<(RuleId, &StyleRule)> = candidates
+            .iter()
+            .filter(|&&rule_id| {
+                let rule = &index.rules[rule_id];
+                rule.selector
+                    .matches(type_name, el_id, el_classes, active_pseudo, structural, ancestors, preceding_siblings, el_attributes)
+            })
+            .map(|&rule_id| (rule_id, &index.rules[rule_id]))
+            .collect();
+
+        matched.sort_by(|(i, _a), (j, _b)| {
+            index.rule_specificities[*i]
+                .cmp(&index.rule_specificities[*j])
+                .then_with(|| i.cmp(j))
+        });
+
+        Some(matched.into_iter().map(|(_, rule)| &rule.properties).collect())
+    }
+
     pub fn matching_rules<'a>(
         &'a self,
         type_name: &str,
@@ -552,6 +608,10 @@ impl StyleSheet {
         preceding_siblings: &[AncestorInfo],
         el_attributes: &HashMap<String, String>,
     ) -> Vec<&'a HashMap<String, String>> {
+        if let Some(matched) = self.query_index(type_name, el_id, el_classes, active_pseudo, structural, ancestors, preceding_siblings, el_attributes) {
+            return matched;
+        }
+
         let mut matched: Vec<(usize, &StyleRule)> = self
             .rules
             .iter()