Before.cs

using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Functions.Strings
{
    public class Before : FunctionTwoScalarVariables
    {
        public Before(ScriptNode String, ScriptNode Delimiter, int Start, int Length, Expression Expression)
            : base(String, Delimiter, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Before);
 
        public override string[] DefaultArgumentNames => new string[] { "s", "Delimiter" };
 
        public override IElement EvaluateScalar(string Argument1, string Argument2, Variables Variables)
        {
            int i = Argument1?.IndexOf(Argument2) ?? -1;
            if (i < 0)
                return ObjectValue.Null;
            else
                return new StringValue(Argument1.Substring(0, i));
        }
 
    }
}