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.aggregates.scalar;
  
  import java.util.function.Supplier;
  
  import org.apache.asterix.om.functions.IFunctionDescriptor;
  import org.apache.asterix.om.functions.IFunctionDescriptorFactory;
  import org.apache.asterix.om.typecomputer.impl.TypeComputeUtils;
  import org.apache.asterix.om.types.BuiltinType;
  import org.apache.asterix.om.types.IAType;
  import org.apache.asterix.runtime.aggregates.base.AbstractAggregateFunctionDynamicDescriptor;
  import org.apache.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
  import org.apache.asterix.runtime.functions.FunctionTypeInferers;
  import org.apache.asterix.runtime.unnestingfunctions.std.ScanCollectionDescriptor.ScanCollectionUnnestingFunctionFactory;
  import org.apache.asterix.runtime.utils.DescriptorFactoryUtil;
  import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
  import org.apache.hyracks.algebricks.runtime.base.IAggregateEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IAggregateEvaluatorFactory;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
  import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
  import org.apache.hyracks.algebricks.runtime.evaluators.ColumnAccessEvalFactory;
  import org.apache.hyracks.api.context.IEvaluatorContext;
  import org.apache.hyracks.api.exceptions.HyracksDataException;
  import org.apache.hyracks.api.exceptions.SourceLocation;
  
  public abstract class AbstractScalarAggregateDescriptor extends AbstractScalarFunctionDynamicDescriptor {
      private static final long serialVersionUID = 1L;
  
      protected final AbstractAggregateFunctionDynamicDescriptor aggFuncDesc;
  
      public AbstractScalarAggregateDescriptor(IFunctionDescriptorFactory aggFuncDescFactory) {
          this.aggFuncDesc = (AbstractAggregateFunctionDynamicDescriptor) aggFuncDescFactory.createFunctionDescriptor();
      }
  
      @Override
      public void setSourceLocation(SourceLocation sourceLoc) {
          super.setSourceLocation(sourceLoc);
          aggFuncDesc.setSourceLocation(sourceLoc);
      }
  
      @Override
      public IScalarEvaluatorFactory createEvaluatorFactory(final IScalarEvaluatorFactory[] args)
              throws AlgebricksException {
  
          // The aggregate function will get a SingleFieldFrameTupleReference that points to the result of the
          // ScanCollection. The list-item will always reside in the first field (column) of the
          // SingleFieldFrameTupleReference.
          int numArgs = args.length;
          IScalarEvaluatorFactory[] aggFuncArgs = new IScalarEvaluatorFactory[numArgs];
  
          aggFuncArgs[0] = new ColumnAccessEvalFactory(0);
  
          for (int i = 1; i < numArgs; ++i) {
              aggFuncArgs[i] = args[i];
          }
          // Create aggregate function from this scalar version.
          final IAggregateEvaluatorFactory aggFuncFactory = aggFuncDesc.createAggregateEvaluatorFactory(aggFuncArgs);
  
          return new IScalarEvaluatorFactory() {
              private static final long serialVersionUID = 1L;
  
              @Override
              public IScalarEvaluator createScalarEvaluator(IEvaluatorContext ctx) throws HyracksDataException {
                  // Use ScanCollection to iterate over list items.
                  ScanCollectionUnnestingFunctionFactory scanCollectionFactory =
                          new ScanCollectionUnnestingFunctionFactory(args[0], sourceLoc, getIdentifier());
                  return createScalarAggregateEvaluator(aggFuncFactory.createAggregateEvaluator(ctx),
                          scanCollectionFactory, ctx);
              }
          };
      }
  
      protected IScalarEvaluator createScalarAggregateEvaluator(IAggregateEvaluator aggEval,
              ScanCollectionUnnestingFunctionFactory scanCollectionFactory, IEvaluatorContext ctx)
              throws HyracksDataException {
          return new GenericScalarAggregateFunction(aggEval, scanCollectionFactory, ctx, sourceLoc);
      }
  
      static IAType getItemType(IAType listType) {
          IAType itemType = TypeComputeUtils.extractListItemType(listType);
          return itemType != null ? itemType : BuiltinType.ANY;
      }
  
      public static IFunctionDescriptorFactory createDescriptorFactory(Supplier<IFunctionDescriptor> descriptorSupplier) {
          return DescriptorFactoryUtil.createFactory(descriptorSupplier, FunctionTypeInferers.SET_ARGUMENT_TYPE);
      }
  }
  