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