using Newtonsoft.Json.Serialization;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace LiveForum.Code.JsonConverterExtend;

public class NullToEmptyStringContractResolver : CamelCasePropertyNamesContractResolver
{
    protected override IValueProvider CreateMemberValueProvider(MemberInfo member)
    {
        var valueProvider = base.CreateMemberValueProvider(member);

        // 处理字符串属性（包括可空字符串）
        if (member is PropertyInfo property &&
            (property.PropertyType == typeof(string) ||
             (property.PropertyType.IsGenericType &&
              property.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>) &&
              property.PropertyType.GetGenericArguments()[0] == typeof(string))))
        {
            return new StringValueProvider(valueProvider);
        }

        return valueProvider;
    }

    private class StringValueProvider : IValueProvider
    {
        private readonly IValueProvider _innerProvider;

        public StringValueProvider(IValueProvider innerProvider)
        {
            _innerProvider = innerProvider;
        }

        public void SetValue(object target, object value)
        {
            _innerProvider.SetValue(target, value);
        }

        public object GetValue(object target)
        {
            var value = _innerProvider.GetValue(target);
            return value ?? string.Empty;
        }
    }
}