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 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.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;
  
  /**
   * This function takes 2 arguments, first argument is a list of strings, and second argument is a string separator,
   * the function concatenates the strings in the first list argument together and returns that as a result.
   *
   * If only a single string is passed in the list, the separator is not added to the result.
   *
   * The behavior is as follows:
   * - If the first argument is a list of strings, and the second argument is a string, concatenated string is returned.
   * - If any argument is missing, missing is returned.
   * - If any argument is null, null is returned.
   * - If any item is not a string, or the array is containing non-strings, null is returned.
   *
   * Examples:
   * string_join(["1", "2"], "-") -> "1-2"
   * string_join(["1"], "-") -> "1"
   */
  @MissingNullInOutFunction
  public class StringJoinDescriptor extends AbstractScalarFunctionDynamicDescriptor {
  
      private static final long serialVersionUID = 1L;
      public static final IFunctionDescriptorFactory FACTORY = StringJoinDescriptor::new;
  
      @Override
      public IScalarEvaluatorFactory createEvaluatorFactory(final IScalarEvaluatorFactory[] args) {
          return new IScalarEvaluatorFactory() {
              private static final long serialVersionUID = 1L;
  
              @Override
              public IScalarEvaluator createScalarEvaluator(final IEvaluatorContext ctx) throws HyracksDataException {
                  return new AbstractConcatStringEval(args, ctx, sourceLoc, getIdentifier(), 1) {
  
                      // TODO Need a way to report array of strings is the expected type
                      private final byte[] ARRAY_TYPE = new byte[] { ATypeTag.SERIALIZED_ORDEREDLIST_TYPE_TAG };
  
                      @Override
                      protected boolean isAcceptedType(ATypeTag typeTag) {
                          return typeTag.isListType();
                      }
  
                      @Override
                      protected byte[] getExpectedType() {
                          return ARRAY_TYPE;
                      }
                  };
              }
          };
      }
  
      @Override
      public FunctionIdentifier getIdentifier() {
          return BuiltinFunctions.STRING_JOIN;
      }
  }
  