using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Security.AccessControl;

namespace ChangkeTec.Utils
{
    public static class TransHelper<TIn, TOut>
    {

        private static readonly Func<TIn, TOut> Cache = GetFunc();
        private static Func<TIn, TOut> GetFunc()
        {
            var parameterExpression = Expression.Parameter(typeof(TIn), "p");
            var memberBindingList = new List<MemberBinding>();

            foreach (var item in typeof(TOut).GetProperties())
            {
                if (!item.CanWrite) continue;
                var inProp = typeof(TIn).GetProperty(item.Name);
                if (inProp==null) continue;
                var outProp = Expression.Property(parameterExpression, inProp);
                MemberBinding memberBinding = Expression.Bind(item, outProp);
                memberBindingList.Add(memberBinding);
            }

            var memberInitExpression = Expression.MemberInit(Expression.New(typeof(TOut)), memberBindingList.ToArray());
            var lambda = Expression.Lambda<Func<TIn, TOut>>(memberInitExpression, new ParameterExpression[] { parameterExpression });

            return lambda.Compile();
        }

        public static TOut Trans(TIn tIn)
        {
            return Cache(tIn);
        }

    }
}