DecCounter.cs

using System.Threading.Tasks;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
 
namespace Waher.Script.Persistence.Functions
{
    public class DecCounter : FunctionMultiVariate
    {
        public DecCounter(ScriptNode Key, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Key }, argumentTypes1Scalar, Start, Length, Expression)
        {
        }
 
        public DecCounter(ScriptNode Key, ScriptNode Amount, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Key, Amount }, argumentTypes2Scalar, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(DecCounter);
 
        public override string[] DefaultArgumentNames => new string[] { "Key", "Amount" };
 
        public override bool IsAsynchronous => true;
 
        public override IElement Evaluate(IElement[] Arguments, Variables Variables)
        {
            return this.EvaluateAsync(Arguments, Variables).Result; 
        }
 
        public override async Task<IElement> EvaluateAsync(IElement[] Arguments, Variables Variables)
        {
            long Count;
 
            if (!(Arguments[0].AssociatedObjectValue is string Key))
                throw new ScriptRuntimeException("Key must be a string.", this);
 
            if (Arguments.Length == 2)
            {
                double N = Expression.ToDouble(Arguments[1].AssociatedObjectValue);
                long Amount = (long)N;
 
                if (Amount != N)
                    throw new ScriptRuntimeException("Amounts must be integers.", this);
 
                Count = await Runtime.Counters.RuntimeCounters.DecrementCounter(Key, Amount);
            }
            else
            {
                Count = await Runtime.Counters.RuntimeCounters.DecrementCounter(Key);
            }
        
            return new DoubleNumber(Count);
        }
    }
}