using System;
using System.Text;
using Newtonsoft.Json;

namespace NzbDrone.Common.Serializer
{
    public class UnderscoreStringEnumConverter : JsonConverter
    {
        public object UnknownValue { get; set; }

        public UnderscoreStringEnumConverter(object unknownValue)
        {
            UnknownValue = unknownValue;
        }

        public override bool CanConvert(Type objectType)
        {
            return objectType.IsEnum;
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            var enumString = reader.Value.ToString().Replace("_", string.Empty);

            try
            {
                return Enum.Parse(objectType, enumString, true);
            }
            catch
            {
                if (UnknownValue == null)
                {
                    throw;
                }

                return UnknownValue;
            }
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            var enumText = value.ToString();
            var builder = new StringBuilder(enumText.Length + 4);
            builder.Append(char.ToLower(enumText[0]));
            for (var i = 1; i < enumText.Length; i++)
            {
                if (char.IsUpper(enumText[i]))
                {
                    builder.Append('_');
                }

                builder.Append(char.ToLower(enumText[i]));
            }

            enumText = builder.ToString();

            writer.WriteValue(enumText);
        }
    }
}