FnStartsWith.java

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 * 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
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 * 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
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 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
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package gov.nist.secauto.metaschema.core.metapath.function.library;

import gov.nist.secauto.metaschema.core.metapath.DynamicContext;
import gov.nist.secauto.metaschema.core.metapath.ISequence;
import gov.nist.secauto.metaschema.core.metapath.MetapathConstants;
import gov.nist.secauto.metaschema.core.metapath.function.FunctionUtils;
import gov.nist.secauto.metaschema.core.metapath.function.IArgument;
import gov.nist.secauto.metaschema.core.metapath.function.IFunction;
import gov.nist.secauto.metaschema.core.metapath.item.IItem;
import gov.nist.secauto.metaschema.core.metapath.item.atomic.IBooleanItem;
import gov.nist.secauto.metaschema.core.metapath.item.atomic.IStringItem;
import gov.nist.secauto.metaschema.core.util.ObjectUtils;

import java.util.List;

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

public final class FnStartsWith {

  @NonNull
  static final IFunction SIGNATURE = IFunction.builder()
      .name("starts-with")
      .namespace(MetapathConstants.NS_XPATH_FUNCTIONS)
      .argument(IArgument.newBuilder()
          .name("arg1").type(IStringItem.class)
          .zeroOrOne()
          .build())
      .argument(IArgument.newBuilder()
          .name("arg2")
          .type(IStringItem.class)
          .zeroOrOne()
          .build())
      .returnType(IBooleanItem.class)
      .returnOne()
      .functionHandler(FnStartsWith::execute)
      .build();

  @SuppressWarnings("unused")
  @NonNull
  private static ISequence<IBooleanItem> execute(@NonNull IFunction function,
      @NonNull List<ISequence<?>> arguments,
      @NonNull DynamicContext dynamicContext,
      IItem focus) {
    IStringItem arg1 = FunctionUtils.getFirstItem(
        FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(0))), true);
    IStringItem arg2 = FunctionUtils.getFirstItem(
        FunctionUtils.asType(ObjectUtils.requireNonNull(arguments.get(1))), true);

    return ISequence.of(fnStartsWith(arg1, arg2));
  }

  private FnStartsWith() {
    // disable construction
  }

  /**
   * Determine if the string provided in the first argument contains the string in
   * the second argument as a leading substring.
   * <p>
   * Based on the XPath 3.1 <a href=
   * "https://www.w3.org/TR/xpath-functions-31/#func-starts-with">fn:starts-with</a>
   * function.
   *
   * @param arg1
   *          the string to examine
   * @param arg2
   *          the string to check as the leading substring
   * @return {@link IBooleanItem#TRUE} if {@code arg1} starts with {@code arg2},
   *         or {@link IBooleanItem#FALSE} otherwise
   */
  public static IBooleanItem fnStartsWith(@Nullable IStringItem arg1, @Nullable IStringItem arg2) {
    String arg2String = arg2 == null ? "" : arg2.asString();

    boolean retval;
    if (arg2String.isEmpty()) {
      retval = true;
    } else {
      String arg1String = arg1 == null ? "" : arg1.asString();
      retval = arg1String.contains(arg2String);
    }
    return IBooleanItem.valueOf(retval);
  }
}