1 files changed, 92 insertions, 0 deletions
diff --git a/config-model/src/main/java/com/yahoo/schema/FeatureNames.java b/config-model/src/main/java/com/yahoo/schema/FeatureNames.java
new file mode 100644
index 00000000000..0671903194f
--- /dev/null
+++ b/config-model/src/main/java/com/yahoo/schema/FeatureNames.java
@@ -0,0 +1,92 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.schema;
+
+import com.yahoo.searchlib.rankingexpression.Reference;
+
+import java.util.Optional;
+
+/**
+ * Utility methods for query, document and constant rank feature names
+ *
+ * @author bratseth
+ */
+public class FeatureNames {
+
+    public static Reference asConstantFeature(String constantName) {
+        return Reference.simple("constant", quoteIfNecessary(constantName));
+    }
+
+    public static Reference asAttributeFeature(String attributeName) {
+        return Reference.simple("attribute", attributeName);
+    }
+
+    public static Reference asQueryFeature(String propertyName) {
+        return Reference.simple("query", quoteIfNecessary(propertyName));
+    }
+
+    /** Returns true if the given reference is an attribute, constant or query feature */
+    public static boolean isSimpleFeature(Reference reference) {
+        if ( ! reference.isSimple()) return false;
+        String name = reference.name();
+        return name.equals("attribute") || name.equals("constant") || name.equals("query");
+    }
+
+    /** Returns true if this is a constant */
+    public static boolean isConstantFeature(Reference reference) {
+        if ( ! isSimpleFeature(reference)) return false;
+        return reference.name().equals("constant");
+    }
+
+    /** Returns true if this is a query feature */
+    public static boolean isQueryFeature(Reference reference) {
+        if ( ! isSimpleFeature(reference)) return false;
+        return reference.name().equals("query");
+    }
+
+    /** Returns true if this is an attribute feature */
+    public static boolean isAttributeFeature(Reference reference) {
+        if ( ! isSimpleFeature(reference)) return false;
+        return reference.name().equals("attribute");
+    }
+
+    /**
+     * Returns the single argument of the given feature name, without any quotes,
+     * or empty if it is not a valid query, attribute or constant feature name
+     */
+    public static Optional<String> argumentOf(String feature) {
+        Optional<Reference> reference = Reference.simple(feature);
+        if ( reference.isEmpty()) return Optional.empty();
+        if ( ! ( reference.get().name().equals("attribute") ||
+                 reference.get().name().equals("constant") ||
+                 reference.get().name().equals("query")))
+            return Optional.empty();
+
+        return Optional.of(reference.get().arguments().expressions().get(0).toString());
+    }
+
+    private static String quoteIfNecessary(String s) {
+        if (notNeedQuotes(s))
+            return s;
+        else
+            return "\"" + s + "\"";
+    }
+
+    static boolean notNeedQuotes(String s) {
+        // Faster version of the regexp [A-Za-z0-9_][A-Za-z0-9_-]*
+        if (s.isEmpty()) return false;
+        if ( ! isValidFirst(s.charAt(0))) return false;
+        for (int i = 1; i < s.length(); i++) {
+            if (!isValidAny(s.charAt(i))) return false;
+        }
+        return true;
+    }
+    private static boolean isValidFirst(char c) {
+        // [A-Za-z0-9_]
+        return (c == '_') || ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')) || ((c >= '0') && (c <= '9'));
+    }
+    private static boolean isValidAny(char c) {
+        // [A-Za-z0-9_-]*
+        return c == '-' || isValidFirst(c);
+    }
+
+}