Add build step to CDN domainset

Build/lib/domain-deduper.js

@@ -0,0 +1,27 @@
+const Trie = require('./trie');
+
+/**
+ * @param {string[]} inputDomains
+ */
+const domainDeduper = (inputDomains) => {
+  const trie = Trie.from(inputDomains);
+  const sets = new Set(inputDomains);
+
+  for (let j = 0, len = inputDomains.length; j < len; j++) {
+    const d = inputDomains[j];
+    if (d[0] !== '.') {
+      continue;
+    }
+
+    trie.find(d, false).forEach(f => sets.delete(f));
+
+    const a = d.slice(1);
+    if (trie.has(a)) {
+      sets.delete(a);
+    }
+  }
+
+  return Array.from(sets);
+};
+
+module.exports.domainDeduper = domainDeduper;