SelectXmlStr.cs

using System.Threading.Tasks;
using System.Xml;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Xml.Functions
{
    public class SelectXmlStr : FunctionTwoScalarVariables
    {
        public SelectXmlStr(ScriptNode Xml, ScriptNode Name, int Start, int Length, Expression Expression)
            : base(Xml, Name, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(SelectXmlStr);
 
        public override string[] DefaultArgumentNames => new string[] { "XML", "XPath" };
 
        public override bool UpgradeScalarsToSameSet => false;
 
        public override IElement EvaluateScalar(IElement Argument1, IElement Argument2, Variables Variables)
        {
            object Obj = Argument1.AssociatedObjectValue;
            XmlNodeList Result;
 
            if (Obj is null)
                return ObjectValue.Null;
            else if (Obj is XmlNode N)
                Result = SelectXml.Evaluate(N, ToString(Argument2) ?? string.Empty);
            else
                throw new ScriptRuntimeException("XPath expression only operate on XML.", this);
 
            int i, c = Result.Count;
 
            switch (c)
            {
                case 0:
                    return ObjectValue.Null;
 
                case 1:
                    return ToElement(Result[0]);
 
                default:
                    IElement[] Items = new IElement[c];
 
                    for (i = 0; i < c; i++)
                        Items[i] = ToElement(Result[i]);
 
                    return Operators.Vectors.VectorDefinition.Encapsulate(Items, false, this);
            }
        }
 
        public override Task<IElement> EvaluateScalarAsync(IElement Argument1, IElement Argument2, Variables Variables)
        {
            return Task.FromResult(this.EvaluateScalar(Argument1, Argument2, Variables));
        }
 
        public static IElement ToElement(XmlNode Node)
        {
            if (Node is XmlText Text)
                return new StringValue(Text.Value);
            else if (Node is XmlCDataSection CData)
                return new StringValue(CData.Value);
            else if (Node is XmlAttribute Attr)
                return new StringValue(Attr.Value);
            else
            {
                if (Node.HasChildNodes && Node.FirstChild == Node.LastChild && Node.FirstChild is XmlText Text2)
                    return new StringValue(Text2.Value);
                else
                    return new ObjectValue(Node);
            }
        }
 
    }
}