LibWeb: Add a bare implementation of the URL built-in

This only has the constructor implemented for now.

Userland/Libraries/LibWeb/URL/URL.cpp

@@ -8,4 +8,40 @@
 #include <LibWeb/URL/URL.h>
 
 namespace Web::URL {
+
+DOM::ExceptionOr<NonnullRefPtr<URL>> URL::create_with_global_object(Bindings::WindowObject& window_object, String const& url, String const& base)
+{
+    // 1. Let parsedBase be null.
+    Optional<AK::URL> parsed_base;
+    // 2. If base is given, then:
+    if (!base.is_null()) {
+        // 1. Let parsedBase be the result of running the basic URL parser on base.
+        parsed_base = base;
+        // 2. If parsedBase is failure, then throw a TypeError.
+        if (!parsed_base->is_valid())
+            return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid base URL" };
+    }
+    // 3. Let parsedURL be the result of running the basic URL parser on url with parsedBase.
+    AK::URL parsed_url;
+    if (parsed_base.has_value())
+        parsed_url = parsed_base->complete_url(url);
+    else
+        parsed_url = url;
+    // 4. If parsedURL is failure, then throw a TypeError.
+    if (!parsed_url.is_valid())
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid URL" };
+    // 5. Let query be parsedURL’s query, if that is non-null, and the empty string otherwise.
+    auto& query = parsed_url.query().is_null() ? String::empty() : parsed_url.query();
+    // 6. Set this’s URL to parsedURL.
+    // 7. Set this’s query object to a new URLSearchParams object.
+    auto query_object = URLSearchParams::create_with_global_object(window_object, query);
+    VERIFY(!query_object.is_exception()); // The string variant of the constructor can't throw.
+    // 8. Initialize this’s query object with query.
+    auto result_url = URL::create(move(parsed_url), query_object.release_value());
+    // 9. Set this’s query object’s URL object to this.
+    result_url->m_query->m_url = result_url;
+
+    return result_url;
+}
+
 }