using EC.Helper.RabbitFunc.Expressions;
using EC.Helper.RabbitFunc.Runtime;

namespace EC.Helper.RabbitFunc.Extern;

[ExternLambda]
internal class RoundLambdaExpression : SystemLambdaExpression
{
    public RoundLambdaExpression()
        : base(typeof(Math).GetMethod(nameof(Math.Round), new Type[] { typeof(double), typeof(int) }), "round", new BodyExpression(),
              Expression.Parameter(typeof(double), "value"),
              Expression.Parameter(typeof(double), "digits"))
    { }

    private class BodyExpression : Expression
    {
        public override object Eval(RuntimeContext context)
        {
            var value = ParameterExpression.Access<double>(context, "value");
            var digits = (int)ParameterExpression.Access<double>(context, "digits");
            return Math.Round(value, digits);
        }
    }
}