/*
    * 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
   * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
   * 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.antlr.metapath10Lexer;
  import gov.nist.secauto.metaschema.core.metapath.item.ItemUtils;
  import gov.nist.secauto.metaschema.core.metapath.item.node.INodeItem;
  import gov.nist.secauto.metaschema.core.util.CollectionUtil;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import java.util.List;
  import java.util.function.Function;
  import java.util.stream.Stream;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  @SuppressWarnings("PMD.ShortClassName") // intentional
  public enum Axis implements IExpression {
    SELF(metapath10Lexer.KW_SELF, focus -> Stream.of(focus)),
    PARENT(metapath10Lexer.KW_PARENT, focus -> Stream.ofNullable(focus.getParentNodeItem())),
    ANCESTOR(metapath10Lexer.KW_ANCESTOR, INodeItem::ancestor),
    ANCESTOR_OR_SELF(metapath10Lexer.KW_ANCESTOR_OR_SELF, INodeItem::ancestorOrSelf),
    CHILDREN(metapath10Lexer.KW_CHILD, INodeItem::modelItems),
    DESCENDANT(metapath10Lexer.KW_DESCENDANT, INodeItem::descendant),
    DESCENDANT_OR_SELF(metapath10Lexer.KW_DESCENDANT_OR_SELF, INodeItem::descendantOrSelf);
  
    private final int keywordIndex;
    @NonNull
    private final Function<INodeItem, Stream<? extends INodeItem>> action;
  
    Axis(int keywordIndex, @NonNull Function<INodeItem, Stream<? extends INodeItem>> action) {
      this.keywordIndex = keywordIndex;
      this.action = action;
    }
  
    /**
     * The ANTLR keyword for this axis type.
     *
     * @return the keyword
     */
    public int getKeywordIndex() {
      return keywordIndex;
    }
  
    /**
     * Execute the axis operation on the provided {@code focus}.
     *
     * @param focus
     *          the node to operate on
     * @return the result of the axis operation
     */
    @NonNull
    public Stream<? extends INodeItem> execute(@NonNull INodeItem focus) {
      return ObjectUtils.notNull(action.apply(focus));
    }
  
    @Override
    public List<? extends IExpression> getChildren() {
      return CollectionUtil.emptyList();
    }
  
    @Override
    public Class<INodeItem> getBaseResultType() {
      return INodeItem.class;
    }
  
    @Override
    public Class<INodeItem> getStaticResultType() {
      return getBaseResultType();
    }
  
    @Override
    public <RESULT, CONTEXT> RESULT accept(IExpressionVisitor<RESULT, CONTEXT> visitor, CONTEXT context) {
      return visitor.visitAxis(this, context);
    }
 
   @Override
   public ISequence<? extends INodeItem> accept(
       DynamicContext dynamicContext,
       ISequence<?> outerFocus) {
     ISequence<? extends INodeItem> retval;
     if (outerFocus.isEmpty()) {
       retval = ISequence.empty();
     } else {
       retval = ISequence.of(outerFocus.asStream()
           .map(item -> ItemUtils.checkItemIsNodeItemForStep(item))
           .flatMap(item -> {
             assert item != null;
             return execute(item);
           }).distinct());
     }
     return retval;
   }
 }