/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package dev.metaschema.core.metapath.cst.path;
   
   import dev.metaschema.core.metapath.DynamicContext;
   import dev.metaschema.core.metapath.IExpression;
  import dev.metaschema.core.metapath.cst.IExpressionVisitor;
  import dev.metaschema.core.metapath.item.ISequence;
  import edu.umd.cs.findbugs.annotations.NonNull;
  
  /**
   * An expression that finds a child of the {@code left} expression using the
   * {@code right} expression.
   * <p>
   * Based on the XPath 3.1 <a href=
   * "https://www.w3.org/TR/xpath-31/#id-relative-path-expressions">relative path
   * expressions</a>.
   */
  public class RelativeSlashPath
      extends AbstractRelativePathExpression {
  
    /**
     * Construct a new expression that finds a child of the {@code left} expression
     * using the {@code right} expression.
     *
     * @param text
     *          the parsed text of the expression
     * @param left
     *          the context path
     * @param right
     *          the path to evaluate in the context of the left
     */
    public RelativeSlashPath(
        @NonNull String text,
        @NonNull IExpression left,
        @NonNull IExpression right) {
      super(text, left, right);
    }
  
    @Override
    public <RESULT, CONTEXT> RESULT accept(IExpressionVisitor<RESULT, CONTEXT> visitor, CONTEXT context) {
      return visitor.visitRelativeSlashPath(this, context);
    }
  
    @Override
    protected ISequence<?> evaluate(
        DynamicContext dynamicContext,
        ISequence<?> focus) {
      ISequence<?> leftResult = getLeft().accept(dynamicContext, focus);
  
      // ensures the left sequence is list backed
      return leftResult.isEmpty()
          ? ISequence.empty()
          : getRight().accept(dynamicContext, leftResult);
    }
  }