GetElement.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 GetElement : FunctionTwoScalarVariables
    {
        public GetElement(ScriptNode Xml, ScriptNode Name, int Start, int Length, Expression Expression)
            : base(Xml, Name, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(GetElement);
 
        public override string[] DefaultArgumentNames => new string[] { "XML", "Name" };
 
        public override bool UpgradeScalarsToSameSet => false;
 
        public override IElement EvaluateScalar(IElement Argument1, IElement Argument2, Variables Variables)
        {
            object Obj = Argument1.AssociatedObjectValue;
            if (Obj is null)
                return Argument1;
 
            string Name = ToString(Argument2) ?? string.Empty;
            XmlElement Response;
 
            if (Obj is XmlElement E)
                Response = E[Name];
            else if (Obj is XmlDocument Doc)
                Response = Doc.DocumentElement[Name];
            else
                throw new ScriptRuntimeException("XML expected.", this);
 
            if (Response is null)
                return ObjectValue.Null;
            else
                return new ObjectValue(Response);
        }
 
        public override Task<IElement> EvaluateScalarAsync(IElement Argument1, IElement Argument2, Variables Variables)
        {
            return Task.FromResult(this.EvaluateScalar(Argument1, Argument2, Variables));
        }
    }
}