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.model.nodes.objects.BaseEventTypeNode;
  import org.eclipse.milo.opcua.stack.core.UaException;
  import org.eclipse.milo.opcua.stack.core.types.structured.FilterOperand;
  import org.jetbrains.annotations.Nullable;
  
  public interface Operator<T> {
  
      void validate(FilterContext context, FilterOperand[] operands) throws ValidationException;
  
      @Nullable
      T apply(
          OperatorContext context,
          BaseEventTypeNode eventNode,
          FilterOperand[] operands) throws UaException;
  
  }
  