src/java/org/apache/cassandra/cql3/functions/masking/ReplaceMaskingFunction.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.cassandra.cql3.functions.masking;

import java.nio.ByteBuffer;
import java.util.List;

import org.apache.cassandra.cql3.functions.FunctionFactory;
import org.apache.cassandra.cql3.functions.FunctionName;
import org.apache.cassandra.cql3.functions.FunctionParameter;
import org.apache.cassandra.cql3.functions.NativeFunction;
import org.apache.cassandra.db.marshal.AbstractType;

/**
 * A {@link MaskingFunction} that replaces the specified column value by a certain replacement value.
 * <p>
 * The returned replacement value needs to have the same type as the replaced value.
 * <p>
 * For example, given a text column named "username", {@code mask_replace(username, '****')} will return {@code ****}.
 */
public class ReplaceMaskingFunction extends MaskingFunction
{
    public static final String NAME = "replace";

    private ReplaceMaskingFunction(FunctionName name, AbstractType<?> replacedType, AbstractType<?> replacementType)
    {
        super(name, replacementType, replacedType, replacementType);
    }

    @Override
    public Masker masker(ByteBuffer... parameters)
    {
        return new Masker(parameters[0]);
    }

    private static class Masker implements MaskingFunction.Masker
    {
        private final ByteBuffer replacement;

        private Masker(ByteBuffer replacement)
        {
            this.replacement = replacement;
        }

        @Override
        public ByteBuffer mask(ByteBuffer value)
        {
            return replacement;
        }
    }

    /** @return a {@link FunctionFactory} to build new {@link ReplaceMaskingFunction}s. */
    public static FunctionFactory factory()
    {
        return new MaskingFunction.Factory(NAME, FunctionParameter.anyType(true), FunctionParameter.sameAsFirst())
        {
            @Override
            protected NativeFunction doGetOrCreateFunction(List<AbstractType<?>> argTypes, AbstractType<?> receiverType)
            {
                AbstractType<?> replacedType = argTypes.get(0);
                AbstractType<?> replacementType = argTypes.get(1);

                assert replacedType == replacementType
                : String.format("Both arguments should have the same type, but found %s(%s, %s)",
                                name, replacedType.asCQL3Type(), replacementType.asCQL3Type());

                return new ReplaceMaskingFunction(name, replacedType, replacementType);
            }
        };
    }
}