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

namespace EC.Helper.RabbitFunc.Extern;

[ExternLambda]
internal class LogLambdaExpression : SystemLambdaExpression
{
    public LogLambdaExpression()
        : base(typeof(Math).GetMethod(nameof(Math.Log), new Type[] { typeof(double), typeof(double) }), "log", new BodyExpression(),
              Expression.Parameter(typeof(double), "x"),
              Expression.Parameter(typeof(double), "e"))
    { }

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