As.cs

using System;
using System.Reflection;
using System.Threading.Tasks;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Operators.Membership
{
    public class As : BinaryScalarOperator
    {
        public As(ScriptNode Left, ScriptNode Right, int Start, int Length, Expression Expression)
            : base(Left, Right, Start, Length, Expression)
        {
        }
 
        public override IElement Evaluate(IElement Left, IElement Right, Variables Variables)
        {
            if (Right is TypeValue TypeValue)
            {
                Type T = TypeValue.Value;
                object Obj = Left.AssociatedObjectValue;
 
                if (!(Obj is null) && T.GetTypeInfo().IsAssignableFrom(Obj.GetType().GetTypeInfo()))
                    return Left;
                else
                    return ObjectValue.Null;
            }
            else
                return base.Evaluate(Left, Right, Variables);
        }
 
        public override Task<IElement> EvaluateAsync(IElement Left, IElement Right, Variables Variables)
        {
            if (Right is TypeValue TypeValue)
            {
                Type T = TypeValue.Value;
                object Obj = Left.AssociatedObjectValue;
 
                if (!(Obj is null) && T.GetTypeInfo().IsAssignableFrom(Obj.GetType().GetTypeInfo()))
                    return Task.FromResult<IElement>(Left);
                else
                    return Task.FromResult<IElement>(ObjectValue.Null);
            }
            else
                return base.EvaluateAsync(Left, Right, Variables);
        }
 
        public override IElement EvaluateScalar(IElement Left, IElement Right, Variables Variables)
        {
            if (Right is TypeValue TypeValue)
            {
                Type T = TypeValue.Value;
                object Obj = Left.AssociatedObjectValue;
 
                if (!(Obj is null) && T.GetTypeInfo().IsAssignableFrom(Obj.GetType().GetTypeInfo()))
                    return Left;
                else
                    return ObjectValue.Null;
            }
            else
                throw new ScriptRuntimeException("Right operand in an AS operation must be a type value.", this);
        }
 
        public override Task<IElement> EvaluateScalarAsync(IElement Left, IElement Right, Variables Variables)
        {
            if (Right is TypeValue TypeValue)
            {
                Type T = TypeValue.Value;
                object Obj = Left.AssociatedObjectValue;
 
                if (!(Obj is null) && T.GetTypeInfo().IsAssignableFrom(Obj.GetType().GetTypeInfo()))
                    return Task.FromResult<IElement>(Left);
                else
                    return Task.FromResult<IElement>(ObjectValue.Null);
            }
            else
                throw new ScriptRuntimeException("Right operand in an AS operation must be a type value.", this);
        }
 
        public override UpgradeBehaviour ScalarUpgradeBehaviour => UpgradeBehaviour.DifferentTypesOk;
    }
}