Calc.cs

using System.Threading.Tasks;
using System.Xml;
using Waher.Persistence.Attributes;
using Waher.Service.IoTBroker.StateMachines.Model.Attributes;
 
namespace Waher.Service.IoTBroker.StateMachines.Model.Values
{
    public class Calc : ValueNode
    {
        private ExpressionAttribute expression;
 
        public Calc()
            : base()
        {
        }
 
        [DefaultValueNull]
        public string Expression
        {
            get => this.expression?.Expression;
            set => this.expression = new ExpressionAttribute(value, false, this);
        }
 
        public override string LocalName => nameof(Calc);
 
        public override IStateMachineNode Create()
        {
            return new Calc();
        }
 
        public override Task Parse(XmlElement Xml)
        {
            this.expression = new ExpressionAttribute(Xml.InnerText, true, this);
 
            return base.Parse(Xml);
        }
 
        public override Task<object> Evaluate(EvaluationArguments Arguments)
        {
            return this.expression?.Evaluate(Arguments.Variables) ?? Task.FromResult<object>(null);
        }
    }
}