GetSetting.cs

using System.Threading.Tasks;
using Waher.Content;
using Waher.Runtime.Settings;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
 
namespace Waher.Script.Persistence.Functions
{
    public class GetSetting : FunctionMultiVariate
    {
        public GetSetting(ScriptNode Name, ScriptNode DefaultValue, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Name, DefaultValue }, argumentTypes2Scalar, Start, Length, Expression)
        {
        }
 
        public GetSetting(ScriptNode Host, ScriptNode Name, ScriptNode DefaultValue, int Start, int Length, Expression Expression)
            : base(new ScriptNode[] { Host, Name, DefaultValue }, argumentTypes3Scalar, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(GetSetting);
 
        public override string[] DefaultArgumentNames => new string[] { "Name", "DefaultValue" };
 
        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)
        {
            int i = 0;
            int c = Arguments.Length;
            string Host = c < 3 ? null : GetHost(Arguments[i++].AssociatedObjectValue, this);
            string Name = Arguments[i++].AssociatedObjectValue?.ToString();
            object DefaultValue = Arguments[i].AssociatedObjectValue;
            object Result;
 
            if (string.IsNullOrEmpty(Host))
                Result = await RuntimeSettings.GetAsync(Name, DefaultValue);
            else
                Result = await HostSettings.GetAsync(Host, Name, DefaultValue);
 
            return Expression.Encapsulate(Result);
        }
 
        public static string GetHost(object Value, ScriptNode Node)
        {
            if (Value is IHostReference Ref)
                return Ref.Host;
            else if (Value is string s)
                return s;
            else if (Value is null)
                return null;
            else
                throw new ScriptRuntimeException("Expected a host reference, or null.", Node);
        }
    }
}