/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package gov.nist.secauto.metaschema.core.metapath.cst;
   
   import gov.nist.secauto.metaschema.core.metapath.ISequence;
   import gov.nist.secauto.metaschema.core.metapath.TypeMetapathException;
  import gov.nist.secauto.metaschema.core.metapath.function.library.FnData;
  import gov.nist.secauto.metaschema.core.metapath.item.atomic.IAnyAtomicItem;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public abstract class AbstractExpression implements IExpression {
    /**
     * Get the first data item of the provided {@code sequence} cast to an
     * {@link IAnyAtomicItem}.
     *
     * @param sequence
     *          the sequence to get the data item from
     * @param requireSingleton
     *          if {@code true} then a {@link TypeMetapathException} is thrown if
     *          the sequence contains more than one item
     * @return {@code null} if the sequence is empty, or the item otherwise
     * @throws TypeMetapathException
     *           if the sequence contains more than one item and requireSingleton is
     *           {@code true}, or if the data item cannot be cast
     */
    @Nullable
    public static IAnyAtomicItem getFirstDataItem(@NonNull ISequence<?> sequence,
        boolean requireSingleton) {
      return FnData.fnData(sequence).getFirstItem(requireSingleton);
    }
  
    @Override
    public String toString() {
      return CSTPrinter.toString(this);
    }
  }