code: /*
   * Copyright (c) 2019 the Eclipse Milo Authors
   *
   * This program and the accompanying materials are made
   * available under the terms of the Eclipse Public License 2.0
   * which is available at https://www.eclipse.org/legal/epl-2.0/
   *
   * SPDX-License-Identifier: EPL-2.0
   */
  
  package org.eclipse.milo.opcua.sdk.server.events.operators;
  
  import org.eclipse.milo.opcua.sdk.server.events.FilterContext;
  import org.eclipse.milo.opcua.sdk.server.events.OperatorContext;
  import org.eclipse.milo.opcua.sdk.server.events.ValidationException;
  import org.eclipse.milo.opcua.sdk.server.events.conversions.ImplicitConversions;
  import org.eclipse.milo.opcua.sdk.server.model.nodes.objects.BaseEventTypeNode;
  import org.eclipse.milo.opcua.stack.core.BuiltinDataType;
  import org.eclipse.milo.opcua.stack.core.StatusCodes;
  import org.eclipse.milo.opcua.stack.core.UaException;
  import org.eclipse.milo.opcua.stack.core.types.builtin.ExpandedNodeId;
  import org.eclipse.milo.opcua.stack.core.types.builtin.NodeId;
  import org.eclipse.milo.opcua.stack.core.types.structured.FilterOperand;
  import org.jetbrains.annotations.Nullable;
  
  
  public class Cast implements Operator<Object> {
  
      Cast() {}
  
      @Override
      public void validate(FilterContext context, FilterOperand[] operands) throws ValidationException {
          if (operands.length < 2) {
              throw new ValidationException(StatusCodes.Bad_FilterOperandCountMismatch);
          }
      }
  
      @Nullable
      @Override
      public Object apply(
          OperatorContext context,
          BaseEventTypeNode eventNode,
          FilterOperand[] operands) throws UaException {
  
          validate(context, operands);
  
          FilterOperand op0 = operands[0];
          FilterOperand op1 = operands[1];
  
          Object sourceValue = context.resolve(op0, eventNode);
  
          Object dataTypeIdObject = context.resolve(op1, eventNode);
  
          if (dataTypeIdObject instanceof NodeId) {
              NodeId dataTypeId = (NodeId) dataTypeIdObject;
  
              BuiltinDataType dataType = BuiltinDataType.fromNodeId(dataTypeId);
  
              if (dataType != null) {
                  return ImplicitConversions.convert(sourceValue, dataType);
              } else {
                  return null;
              }
          } else if (dataTypeIdObject instanceof ExpandedNodeId) {
              ExpandedNodeId dataTypeId = (ExpandedNodeId) dataTypeIdObject;
  
              BuiltinDataType dataType = BuiltinDataType.fromNodeId(dataTypeId);
  
              if (dataType != null) {
                  return ImplicitConversions.convert(sourceValue, dataType);
              } else {
                  return null;
              }
          } else {
              return null;
          }
      }
  
  }
  