001/*
002 * Portions of this software was developed by employees of the National Institute
003 * of Standards and Technology (NIST), an agency of the Federal Government and is
004 * being made available as a public service. Pursuant to title 17 United States
005 * Code Section 105, works of NIST employees are not subject to copyright
006 * protection in the United States. This software may be subject to foreign
007 * copyright. Permission in the United States and in foreign countries, to the
008 * extent that NIST may hold copyright, to use, copy, modify, create derivative
009 * works, and distribute this software and its documentation without fee is hereby
010 * granted on a non-exclusive basis, provided that this notice and disclaimer
011 * of warranty appears in all copies.
012 *
013 * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
014 * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
015 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
016 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
017 * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
018 * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
019 * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
020 * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
021 * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
022 * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
023 * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
024 * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
025 */
026
027package gov.nist.secauto.metaschema.core.metapath;
028
029import gov.nist.secauto.metaschema.core.metapath.item.IItem;
030
031import java.util.List;
032
033import edu.umd.cs.findbugs.annotations.NonNull;
034
035public interface IExpression {
036  /**
037   * Retrieve the child expressions associated with this expression.
038   *
039   * @return a list of expressions, which may be empty
040   */
041  @NonNull
042  List<? extends IExpression> getChildren();
043
044  /**
045   * The minimum expected result type to be produced when evaluating the
046   * expression. The result may be a sub-class or sub-interface of this value.
047   *
048   * @return the base result type
049   */
050  @NonNull
051  default Class<? extends IItem> getBaseResultType() {
052    return IItem.class;
053  }
054
055  /**
056   * The expected result type produced by evaluating the expression. The result
057   * must be the same or a sub-class or sub-interface of the value provided by
058   * {@link #getBaseResultType()}.
059   * <p>
060   * This method can be overloaded to provide static analysis of the expression to
061   * determine a more specific result type.
062   *
063   * @return the result type
064   */
065  @NonNull
066  default Class<? extends IItem> getStaticResultType() {
067    return getBaseResultType();
068  }
069
070  /**
071   * Produce a string representation of this expression including the expression's
072   * name.
073   * <p>
074   * This method can be overloaded to provide a more appropriate representation of
075   * the expression.
076   *
077   * @return a string representing the data elements of the expression
078   */
079  @SuppressWarnings("null")
080  @NonNull
081  default String toASTString() {
082    return String.format("%s[]", getClass().getName());
083  }
084
085  /**
086   * Provides a double dispatch callback for visitor handling.
087   *
088   * @param dynamicContext
089   *          the dynamic evaluation context
090   * @param focus
091   *          the outer focus of the expression
092   * @return the result of evaluation
093   */
094  @NonNull
095  ISequence<? extends IItem> accept(@NonNull DynamicContext dynamicContext, @NonNull ISequence<?> focus);
096
097  /**
098   * Provides a double dispatch callback for visitor handling.
099   *
100   * @param <RESULT>
101   *          the type of the evaluation result
102   * @param <CONTEXT>
103   *          the type of the visitor context
104   * @param visitor
105   *          the visitor calling this method
106   * @param context
107   *          the visitor context
108   * @return the result of evaluation
109   */
110  <RESULT, CONTEXT> RESULT accept(@NonNull IExpressionVisitor<RESULT, CONTEXT> visitor, @NonNull CONTEXT context);
111}