content: package com.alibaba.qlexpress4.runtime.instruction;
  
  import com.alibaba.qlexpress4.QLOptions;
  import com.alibaba.qlexpress4.exception.ErrorReporter;
  import com.alibaba.qlexpress4.exception.QLErrorCodes;
  import com.alibaba.qlexpress4.runtime.QContext;
  import com.alibaba.qlexpress4.runtime.QResult;
  import com.alibaba.qlexpress4.runtime.Value;
  import com.alibaba.qlexpress4.runtime.data.ArrayItemValue;
  import com.alibaba.qlexpress4.runtime.data.ListItemValue;
  import com.alibaba.qlexpress4.runtime.data.MapItemValue;
  import com.alibaba.qlexpress4.runtime.util.ValueUtils;
  import com.alibaba.qlexpress4.utils.PrintlnUtils;
  
  import java.lang.reflect.Array;
  import java.util.List;
  import java.util.Map;
  import java.util.function.Consumer;
  
  /**
   * Operation: extract value with index, like a[0], m['a']
   * Input: 2, indexable object and index
   * Output: 1
   * <p>
   * Author: DQinYuan
   */
  public class IndexInstruction extends QLInstruction {
      
      public IndexInstruction(ErrorReporter errorReporter) {
          super(errorReporter);
      }
      
      @SuppressWarnings("unchecked")
      @Override
      public QResult execute(QContext qContext, QLOptions qlOptions) {
          Object index = qContext.pop().get();
          Object indexAble = qContext.pop().get();
          if (indexAble instanceof List) {
              Number indexNumber = ValueUtils.assertType(index,
                  Number.class,
                  QLErrorCodes.INVALID_INDEX.name(),
                  QLErrorCodes.INVALID_INDEX.getErrorMsg(),
                  errorReporter);
              List<? super Object> list = (List<? super Object>)indexAble;
              int intIndex = ValueUtils.javaIndex(list.size(), indexNumber.intValue());
              if (intIndex < 0 || intIndex >= list.size()) {
                  throw errorReporter.report(QLErrorCodes.INDEX_OUT_BOUND.name(),
                      QLErrorCodes.INDEX_OUT_BOUND.getErrorMsg());
              }
              qContext.push(new ListItemValue(list, intIndex));
          }
          else if (indexAble instanceof Map) {
              qContext.push(new MapItemValue((Map<?, ?>)indexAble, index));
          }
          else if (indexAble != null && indexAble.getClass().isArray()) {
              Number indexNumber = ValueUtils.assertType(index,
                  Number.class,
                  QLErrorCodes.INVALID_INDEX.name(),
                  QLErrorCodes.INVALID_INDEX.getErrorMsg(),
                  errorReporter);
              int arrLen = Array.getLength(indexAble);
              int intIndex = ValueUtils.javaIndex(arrLen, indexNumber.intValue());
              if (intIndex < 0 || intIndex >= arrLen) {
                  throw errorReporter.report(QLErrorCodes.INDEX_OUT_BOUND.name(),
                      QLErrorCodes.INDEX_OUT_BOUND.getErrorMsg());
              }
              qContext.push(new ArrayItemValue(indexAble, intIndex));
          }
          else if (indexAble == null && qlOptions.isAvoidNullPointer()) {
              qContext.push(Value.NULL_VALUE);
          }
          else {
              throw errorReporter.reportFormat(QLErrorCodes.NONINDEXABLE_OBJECT.name(),
                  QLErrorCodes.NONINDEXABLE_OBJECT.getErrorMsg(),
                  indexAble == null ? "null" : indexAble.getClass().getName());
          }
          return QResult.NEXT_INSTRUCTION;
      }
      
      @Override
      public int stackInput() {
          return 2;
      }
      
      @Override
      public int stackOutput() {
          return 1;
      }
      
      @Override
      public void println(int index, int depth, Consumer<String> debug) {
          PrintlnUtils.printlnByCurDepth(depth, index + ": Index", debug);
      }
  }
  