AbstractFilterExpression.java

/*
 * Portions of this software was developed by employees of the National Institute
 * of Standards and Technology (NIST), an agency of the Federal Government and is
 * being made available as a public service. Pursuant to title 17 United States
 * Code Section 105, works of NIST employees are not subject to copyright
 * protection in the United States. This software may be subject to foreign
 * copyright. Permission in the United States and in foreign countries, to the
 * extent that NIST may hold copyright, to use, copy, modify, create derivative
 * works, and distribute this software and its documentation without fee is hereby
 * granted on a non-exclusive basis, provided that this notice and disclaimer
 * of warranty appears in all copies.
 *
 * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
 * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
 * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
 * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
 * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
 * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
 * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
 * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
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 * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
 */

package gov.nist.secauto.metaschema.core.metapath;

import gov.nist.secauto.metaschema.core.metapath.item.IItem;

import java.util.List;

import edu.umd.cs.findbugs.annotations.NonNull;

abstract class AbstractFilterExpression
    extends AbstractBinaryExpression<IExpression, IExpression> {

  @NonNull
  private final Class<? extends IItem> staticResultType;

  /**
   * Construct a new filter expression.
   *
   * @param left
   *          an expression indicating the items to filter
   * @param right
   *          an expression indicating the items to use as the filter
   */
  @SuppressWarnings("null")
  public AbstractFilterExpression(@NonNull IExpression left, @NonNull IExpression right) {
    super(left, right);
    this.staticResultType = ExpressionUtils.analyzeStaticResultType(IItem.class, List.of(left, right));
  }

  @Override
  public Class<? extends IItem> getStaticResultType() {
    return staticResultType;
  }

  @Override
  public ISequence<? extends IItem> accept(
      @NonNull DynamicContext dynamicContext,
      @NonNull ISequence<?> focus) {

    ISequence<?> left = getLeft().accept(dynamicContext, focus);
    ISequence<?> right = getRight().accept(dynamicContext, focus);
    List<? extends IItem> rightList = right.asList();

    return applyFilterTo(left, rightList);
  }

  /**
   * A callback used to apply the filter to the result of evaluating the left
   * expression.
   *
   * @param result
   *          the set of items to filter
   * @param items
   *          a list of items to filter with
   * @return the filtered result set
   */
  @NonNull
  protected abstract ISequence<?> applyFilterTo(
      @NonNull ISequence<?> result,
      @NonNull List<? extends IItem> items);
}