/*
    * 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.function.library.FnBoolean;
  import gov.nist.secauto.metaschema.core.metapath.item.IItem;
  import gov.nist.secauto.metaschema.core.util.ObjectUtils;
  
  import java.math.BigInteger;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  class Predicate implements IExpression {
    @NonNull
    private final IExpression base;
    @NonNull
    private final List<IExpression> predicates;
  
    /**
     * Construct a new predicate expression.
     *
     * @param base
     *          the base to evaluate against
     * @param predicates
     *          the expression(s) to apply as a filter
     */
    protected Predicate(@NonNull IExpression base, @NonNull List<IExpression> predicates) {
      this.base = base;
      this.predicates = predicates;
    }
  
    /**
     * Get the base sub-expression.
     *
     * @return the sub-expression
     */
    @NonNull
    public IExpression getBase() {
      return base;
    }
  
    /**
     * Retrieve the list of predicates to filter with.
     *
     * @return the list of predicates
     */
    @NonNull
    public List<IExpression> getPredicates() {
      return predicates;
    }
  
    @Override
    public List<? extends IExpression> getChildren() {
      return ObjectUtils.notNull(
          Stream.concat(Stream.of(getBase()), getPredicates().stream()).collect(Collectors.toList()));
    }
  
    @Override
    public @NonNull ISequence<? extends IItem> accept(@NonNull DynamicContext dynamicContext,
        @NonNull ISequence<?> focus) {
  
      ISequence<?> retval = getBase().accept(dynamicContext, focus);
  
      if (dynamicContext.getConfiguration().isFeatureEnabled(MetapathEvaluationFeature.METAPATH_EVALUATE_PREDICATES)) {
        // evaluate the predicates for this step
        AtomicInteger index = new AtomicInteger();
  
        Stream<? extends IItem> stream = ObjectUtils.notNull(
            retval.asStream().map(item -> {
              // build a positional index of the items
             return Map.entry(BigInteger.valueOf(index.incrementAndGet()), item);
           }).filter(entry -> {
             @SuppressWarnings("null")
             @NonNull IItem item = entry.getValue();
 
             // return false if any predicate evaluates to false
             return !predicates.stream()
                 .map(predicateExpr -> {
                   boolean bool;
                   if (predicateExpr instanceof IntegerLiteral) {
                     // reduce the result to the matching item
                     BigInteger predicateIndex = ((IntegerLiteral) predicateExpr).getValue();
 
                     // get the position of the item
                     final BigInteger position = entry.getKey();
 
                     // it is a match if the position matches
                     bool = position.equals(predicateIndex);
                   } else {
                     ISequence<?> innerFocus = ISequence.of(item);
                     ISequence<?> predicateResult = predicateExpr.accept(dynamicContext, innerFocus);
                     bool = FnBoolean.fnBoolean(predicateResult).toBoolean();
                   }
                   return bool;
                 }).anyMatch(x -> !x);
           }).map(entry -> entry.getValue()));
 
       retval = ISequence.of(stream);
     }
     return retval;
   }
 
   @Override
   public <RESULT, CONTEXT> RESULT accept(@NonNull IExpressionVisitor<RESULT, CONTEXT> visitor, CONTEXT context) {
     return visitor.visitPredicate(this, context);
   }
 
 }