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

namespace DDD
{
    public static class BindingPath
    {
        public static string For<TViewModel, TProp>(Expression<Func<TViewModel, TProp>> expression)
        {
            if (expression == null) throw new ArgumentNullException(nameof(expression));

            Expression expr = expression.Body;

            // 값형식 → object 캐스팅 제거
            if (expr is UnaryExpression unary && unary.NodeType == ExpressionType.Convert)
            {
                expr = unary.Operand;
            }

            var members = new Stack<string>();
            while (expr is MemberExpression me)
            {
                members.Push(me.Member.Name);
                expr = me.Expression;

                if (expr is ParameterExpression) break; // 루트 도달

                if (expr is UnaryExpression innerUnary && innerUnary.NodeType == ExpressionType.Convert)
                    expr = innerUnary.Operand;
            }

            return string.Join(".", members);
        }

        // 편의용: object 리턴 시그니처도 지원
        public static string For<TViewModel>(Expression<Func<TViewModel, object>> expression)
        {
            if (expression == null) throw new ArgumentNullException(nameof(expression));
            Expression expr = expression.Body;
            if (expr is UnaryExpression unary && unary.NodeType == ExpressionType.Convert)
                expr = unary.Operand;

            var members = new Stack<string>();
            while (expr is MemberExpression me)
            {
                members.Push(me.Member.Name);
                expr = me.Expression;
                if (expr is ParameterExpression) break;
                if (expr is UnaryExpression innerUnary && innerUnary.NodeType == ExpressionType.Convert)
                    expr = innerUnary.Operand;
            }
            return string.Join(".", members);
        }
    }
}