using Newtonsoft.Json;
using System;
using System.Linq;
using System.Reflection;

namespace TMDbLib.Utilities.Converters
{
    public class TolerantEnumConverter : JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            Type type = IsNullableType(objectType) ? Nullable.GetUnderlyingType(objectType) : objectType;
            return type.GetTypeInfo().IsEnum;
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            bool isNullable = IsNullableType(objectType);
            Type enumType = isNullable ? Nullable.GetUnderlyingType(objectType) : objectType;

            string[] names = Enum.GetNames(enumType);

            if (reader.TokenType == JsonToken.String)
            {
                string enumText = reader.Value.ToString();

                if (!string.IsNullOrEmpty(enumText))
                {
                    string match = names.FirstOrDefault(n => string.Equals(n, enumText, StringComparison.OrdinalIgnoreCase));

                    if (match != null)
                    {
                        return Enum.Parse(enumType, match);
                    }
                }
            }
            else if (reader.TokenType == JsonToken.Integer)
            {
                int enumVal = Convert.ToInt32(reader.Value);
                int[] values = (int[])Enum.GetValues(enumType);
                if (values.Contains(enumVal))
                {
                    return Enum.Parse(enumType, enumVal.ToString());
                }
            }

            if (!isNullable)
            {
                string defaultName = names.FirstOrDefault(n => string.Equals(n, "Unknown", StringComparison.OrdinalIgnoreCase)) ?? names.First();

                return Enum.Parse(enumType, defaultName);
            }

            return null;
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            writer.WriteValue(value.ToString());
        }

        private static bool IsNullableType(Type t)
        {
            return t.GetTypeInfo().IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>);
        }
    }
}