content: /*
   * 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;
  
  import org.apache.cassandra.db.marshal.AbstractType;
  import org.apache.cassandra.db.marshal.UTF8Type;
  import org.apache.cassandra.exceptions.InvalidRequestException;
  import org.apache.cassandra.transport.ProtocolVersion;
  import org.apache.cassandra.utils.ByteBufferUtil;
  
  import java.nio.ByteBuffer;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  import static java.lang.String.format;
  
  public class ToJsonFct extends NativeScalarFunction
  {
      private static final Map<AbstractType<?>, ToJsonFct> instances = new ConcurrentHashMap<>();
  
      public static ToJsonFct getInstance(String name, List<AbstractType<?>> argTypes) throws InvalidRequestException
      {
          if (argTypes.size() != 1)
              throw new InvalidRequestException(format("%s() only accepts one argument (got %d)", name, argTypes.size()));
  
          AbstractType<?> fromType = argTypes.get(0);
          ToJsonFct func = instances.get(fromType);
          if (func == null)
          {
              func = new ToJsonFct(name, fromType);
              instances.put(fromType, func);
          }
          return func;
      }
  
      private ToJsonFct(String name, AbstractType<?> argType)
      {
          super(name, UTF8Type.instance, argType);
      }
  
      @Override
      public Arguments newArguments(ProtocolVersion version)
      {
          return new FunctionArguments(version, (protocolVersion, buffer) -> {
              AbstractType<?> argType = argTypes.get(0);
  
              if (buffer == null || (!buffer.hasRemaining() && argType.isEmptyValueMeaningless()))
                  return null;
  
              return argTypes.get(0).toJSONString(buffer, protocolVersion);
          });
      }
  
      @Override
      public ByteBuffer execute(Arguments arguments) throws InvalidRequestException
      {
          if (arguments.containsNulls())
              return ByteBufferUtil.bytes("null");
  
          return ByteBufferUtil.bytes(arguments.<String>get(0));
      }
  
      public static void addFunctionsTo(NativeFunctions functions)
      {
          functions.add(new Factory("to_json"));
          functions.add(new Factory("tojson")); // deprecated pre-5.0 name
      }
  
      private static class Factory extends FunctionFactory
      {
          public Factory(String name)
          {
              super(name, FunctionParameter.anyType(false));
          }
  
          @Override
          protected NativeFunction doGetOrCreateFunction(List<AbstractType<?>> argTypes, AbstractType<?> receiverType)
          {
              return ToJsonFct.getInstance(name.name, argTypes);
          }
      }
  }
  