OnCondition.cs

using System.Text;
using System.Threading.Tasks;
using System.Xml;
using Waher.Persistence.Attributes;
using Waher.Service.IoTBroker.StateMachines.EventHandlers;
using Waher.Service.IoTBroker.StateMachines.Model.Attributes;
using Waher.Service.IoTBroker.StateMachines.Model.States;
 
namespace Waher.Service.IoTBroker.StateMachines.Model.Events
{
    public class OnCondition : EventNode
    {
        private ExpressionAttribute condition;
 
        public OnCondition()
            : base()
        {
        }
 
        [DefaultValueNull]
        public string Condition
        {
            get => this.condition?.Expression;
            set => this.condition = new ExpressionAttribute(value, false, this);
        }
 
        public override string LocalName => nameof(OnCondition);
 
        public override IStateMachineNode Create()
        {
            return new OnCondition();
        }
 
        public override Task Parse(XmlElement Xml)
        {
            this.condition = new ExpressionAttribute(Xml.InnerText, true, this);
 
            return base.Parse(Xml);
        }
 
        public override Task<EventHandlerReference> Register(int EventIndex, EvaluationArguments Arguments, OnEvent Event)
        {
            return this.StateUpdated(Arguments);
        }
 
        public override Task Unregister(int EventIndex, EvaluationArguments Arguments)
        {
            return Task.CompletedTask;
        }
 
        public override async Task<EventHandlerReference> StateUpdated(EvaluationArguments Arguments)
        {
            if (this.condition is null)
                return null;
 
            if (await this.condition.Evaluate(Arguments.Variables) is bool b && b)
                return new EventHandlerReference(null, true);
 
            return null;
        }
 
        public override string Label
        {
            get
            {
                StringBuilder sb = new StringBuilder();
 
                sb.Append('[');
                sb.Append(this.condition.Expression);
                sb.Append(']');
 
                return sb.ToString();
            }
        }
    }
}