BooleanFunctions.cs

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using System;
using System.Xml.XPath;
using System.Xml.Xsl;
 
namespace MS.Internal.Xml.XPath;
 
internal sealed class BooleanFunctions : ValueQuery
{
    private readonly Query _arg;
 
    private readonly Function.FunctionType _funcType;
 
    public override XPathResultType StaticType => XPathResultType.Boolean;
 
    public BooleanFunctions(Function.FunctionType funcType, Query arg)
    {
        _arg = arg;
        _funcType = funcType;
    }
 
    private BooleanFunctions(BooleanFunctions other)
        : base(other)
    {
        _arg = Query.Clone(other._arg);
        _funcType = other._funcType;
    }
 
    public override void SetXsltContext(XsltContext context)
    {
        if (_arg != null)
        {
            _arg.SetXsltContext(context);
        }
    }
 
    public override object Evaluate(XPathNodeIterator nodeIterator)
    {
        return _funcType switch
        {
            Function.FunctionType.FuncBoolean => toBoolean(nodeIterator), 
            Function.FunctionType.FuncNot => Not(nodeIterator), 
            Function.FunctionType.FuncTrue => true, 
            Function.FunctionType.FuncFalse => false, 
            Function.FunctionType.FuncLang => Lang(nodeIterator), 
            _ => false, 
        };
    }
 
    internal static bool toBoolean(double number)
    {
        if (number != 0.0)
        {
            return !double.IsNaN(number);
        }
        return false;
    }
 
    internal static bool toBoolean(string str)
    {
        return str.Length > 0;
    }
 
    internal bool toBoolean(XPathNodeIterator nodeIterator)
    {
        object obj = _arg.Evaluate(nodeIterator);
        if (obj is XPathNodeIterator)
        {
            return _arg.Advance() != null;
        }
        if (obj is string str)
        {
            return toBoolean(str);
        }
        if (obj is double)
        {
            return toBoolean((double)obj);
        }
        if (obj is bool)
        {
            return (bool)obj;
        }
        return true;
    }
 
    private bool Not(XPathNodeIterator nodeIterator)
    {
        return !(bool)_arg.Evaluate(nodeIterator);
    }
 
    private bool Lang(XPathNodeIterator nodeIterator)
    {
        string text = _arg.Evaluate(nodeIterator).ToString();
        string xmlLang = nodeIterator.Current.XmlLang;
        if (xmlLang.StartsWith(text, StringComparison.OrdinalIgnoreCase))
        {
            if (xmlLang.Length != text.Length)
            {
                return xmlLang[text.Length] == '-';
            }
            return true;
        }
        return false;
    }
 
    public override XPathNodeIterator Clone()
    {
        return new BooleanFunctions(this);
    }
}