LoopFocus.cs

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using System.Xml.Xsl.Qil;
using System.Xml.Xsl.XPath;
 
namespace System.Xml.Xsl.Xslt;
 
internal struct LoopFocus : IFocus
{
    private readonly XPathQilFactory _f;
 
    private QilIterator _current;
 
    private QilIterator _cached;
 
    private QilIterator _last;
 
    public bool IsFocusSet => _current != null;
 
    public LoopFocus(XPathQilFactory f)
    {
        _f = f;
        _current = (_cached = (_last = null));
    }
 
    public void SetFocus(QilIterator current)
    {
        _current = current;
        _cached = (_last = null);
    }
 
    public QilNode GetCurrent()
    {
        return _current;
    }
 
    public QilNode GetPosition()
    {
        return _f.XsltConvert(_f.PositionOf(_current), XmlQueryTypeFactory.DoubleX);
    }
 
    public QilNode GetLast()
    {
        if (_last == null)
        {
            _last = _f.Let(_f.Double(0.0));
        }
        return _last;
    }
 
    public void EnsureCache()
    {
        if (_cached == null)
        {
            _cached = _f.Let(_current.Binding);
            _current.Binding = _cached;
        }
    }
 
    public void Sort(QilNode sortKeys)
    {
        if (sortKeys != null)
        {
            EnsureCache();
            _current = _f.For(_f.Sort(_current, sortKeys));
        }
    }
 
    public QilLoop ConstructLoop(QilNode body)
    {
        if (_last != null)
        {
            EnsureCache();
            _last.Binding = _f.XsltConvert(_f.Length(_cached), XmlQueryTypeFactory.DoubleX);
        }
        QilLoop qilLoop = _f.BaseFactory.Loop(_current, body);
        if (_last != null)
        {
            qilLoop = _f.BaseFactory.Loop(_last, qilLoop);
        }
        if (_cached != null)
        {
            qilLoop = _f.BaseFactory.Loop(_cached, qilLoop);
        }
        return qilLoop;
    }
}