using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;

namespace APT.Infrastructure.EF.Extensions
{
    public class IQueryableSelectorExtension
    {
        public static Expression<Func<TSource, TResult>> CreateSelecter<TSource, TResult>(List<string> columns)
        {
            Expression<Func<TSource, TResult>> selector = null;

            //(rec)
            ParameterExpression param = Expression.Parameter(typeof(TSource), "rec");
            //new ParadigmSearchListData 
            var v0 = Expression.New(typeof(TResult));

            var memberBindings = new List<MemberBinding>();
            foreach (var column in columns)
            {
                var left = typeof(TResult).GetProperty(column);

                var right = Expression.Property(param, typeof(TSource).GetProperty(column));

                memberBindings.Add(Expression.Bind(left, right));
            }

            Expression body = Expression.MemberInit(v0,
                           //{ Number = rec.NUMBER, Name = rec.RES_NAME }
                           memberBindings.ToArray());

            selector = (Expression<Func<TSource, TResult>>)Expression.Lambda(body, param);

            return selector;
        }

        private static MemberAssignment GetPropertyLambdaExpression(ParameterExpression param, string field)
        {
            string[] propertyNames = field.Split('.');
            Expression propertyAccess = param;
            Type type = param.Type;
            PropertyInfo property;
            foreach (string propertyName in propertyNames)
            {
                property = type.GetProperty(propertyName);
                if (property != null)
                {
                    type = property.PropertyType;
                    propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);
                }
            }

            //var left = typeof(TResult).GetProperty(column);
            //return Expression.Bind(property, Expression.Lambda(propertyAccess, param));
            //return Expression.Lambda(propertyAccess, param);

            return null;
        }
    }
}