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.asterix.runtime.evaluators.functions;
  
  import static org.apache.asterix.om.types.EnumDeserializer.ATYPETAGDESERIALIZER;
  
  import java.io.IOException;
  
  import org.apache.asterix.common.annotations.MissingNullInOutFunction;
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.asterix.om.functions.IFunctionDescriptorFactory;
  import org.apache.asterix.om.types.ATypeTag;
  import org.apache.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
  import org.apache.asterix.runtime.evaluators.common.ListAccessor;
  import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
  import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
  import org.apache.hyracks.api.context.IEvaluatorContext;
  import org.apache.hyracks.api.exceptions.HyracksDataException;
  import org.apache.hyracks.data.std.api.AbstractPointable;
  import org.apache.hyracks.data.std.api.IPointable;
  import org.apache.hyracks.data.std.primitive.VoidPointable;
  import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
  import org.apache.hyracks.dataflow.common.data.accessors.IFrameTupleReference;
  
  /**
   * <pre>
   * array_ifnull(list) returns the first item it encounters that is not a null or missing. Otherwise, it returns null.
   *
   * It throws an error at compile time if the number of arguments != 1
   *
   * It returns in order:
   * 1. missing if the input list is missing
   * 2. null if the input list is null or is not a list.
   * 3. otherwise, the first non-null non-missing item in the list. Otherwise, null.
   *
   * </pre>
   */
  
  @MissingNullInOutFunction
  public class ArrayIfNullDescriptor extends AbstractScalarFunctionDynamicDescriptor {
      private static final long serialVersionUID = 1L;
  
      public static final IFunctionDescriptorFactory FACTORY = ArrayIfNullDescriptor::new;
  
      @Override
      public FunctionIdentifier getIdentifier() {
          return BuiltinFunctions.ARRAY_IFNULL;
      }
  
      @Override
      public IScalarEvaluatorFactory createEvaluatorFactory(final IScalarEvaluatorFactory[] args)
              throws AlgebricksException {
          return new IScalarEvaluatorFactory() {
              private static final long serialVersionUID = 1L;
  
              @Override
              public IScalarEvaluator createScalarEvaluator(final IEvaluatorContext ctx) throws HyracksDataException {
                  return new ArrayIfNullEval(args, ctx);
              }
          };
      }
  
      public class ArrayIfNullEval implements IScalarEvaluator {
          private final ArrayBackedValueStorage storage;
          private final IScalarEvaluator listArgEval;
          private final IPointable listArg;
          private final ListAccessor listAccessor;
          private final AbstractPointable item;
  
          public ArrayIfNullEval(IScalarEvaluatorFactory[] args, IEvaluatorContext ctx) throws HyracksDataException {
              storage = new ArrayBackedValueStorage();
              listArg = new VoidPointable();
              item = new VoidPointable();
              listAccessor = new ListAccessor();
              listArgEval = args[0].createScalarEvaluator(ctx);
          }
  
          @Override
          public void evaluate(IFrameTupleReference tuple, IPointable result) throws HyracksDataException {
              // get the list argument and make sure it's a list
              listArgEval.evaluate(tuple, listArg);
  
              if (PointableHelper.checkAndSetMissingOrNull(result, listArg)) {
                  return;
              }
  
              byte[] listBytes = listArg.getByteArray();
              int offset = listArg.getStartOffset();
              ATypeTag listType = ATYPETAGDESERIALIZER.deserialize(listBytes[offset]);
              if (!listType.isListType()) {
                  PointableHelper.setNull(result);
                  return;
              }
  
              listAccessor.reset(listBytes, offset);
              ATypeTag itemTypeTag = listAccessor.getItemType();
              try {
                  if (itemTypeTag == ATypeTag.NULL || itemTypeTag == ATypeTag.MISSING) {
                      // list of nulls or list of missings
                      PointableHelper.setNull(result);
                      return;
                  }
  
                  int numItems = listAccessor.size();
                  for (int i = 0; i < numItems; i++) {
                      listAccessor.getOrWriteItem(i, item, storage);
                      itemTypeTag = ATYPETAGDESERIALIZER.deserialize(item.getByteArray()[item.getStartOffset()]);
                      if (itemTypeTag != ATypeTag.NULL && itemTypeTag != ATypeTag.MISSING) {
                          result.set(item);
                          return;
                      }
                  }
                  PointableHelper.setNull(result);
              } catch (IOException e) {
                  throw HyracksDataException.create(e);
              }
          }
      }
  }
  