using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Mime;
using System.Text;
using System.Threading.Tasks;
using Nancy;

namespace Sony.Filtr.AdminAPI.Utility
{
    public static class NancyExtensions
    {
        public static Response WithContentDispositionFileName(this Response response, string filename)
        {
            return response.WithHeader("Content-disposition", GetHeaderValue(filename));
        }

        private static string GetHeaderValue(string fileName)
        {
            foreach (int num in fileName)
            {
                if (num > (int)sbyte.MaxValue)
                    return CreateRfc2231HeaderValue(fileName);
            }
            return $"attachment; filename=\"{fileName}\"";
        }
        private static string CreateRfc2231HeaderValue(string filename)
        {
            StringBuilder builder = new StringBuilder("attachment; filename*=UTF-8''");
            foreach (byte b in Encoding.UTF8.GetBytes(filename))
            {
                if (IsByteValidHeaderValueCharacter(b))
                    builder.Append((char)b);
                else
                    AddByteToStringBuilder(b, builder);
            }
            return builder.ToString();
        }

        private static void AddByteToStringBuilder(byte b, StringBuilder builder)
        {
            builder.Append('%');
            int num = (int)b;
            AddHexDigitToStringBuilder(num >> 4, builder);
            AddHexDigitToStringBuilder(num % 16, builder);
        }

        private static void AddHexDigitToStringBuilder(int digit, StringBuilder builder)
        {
            builder.Append("0123456789ABCDEF"[digit]);
        }

        private static bool IsByteValidHeaderValueCharacter(byte b)
        {
            if (48 <= b && b <= 57 || 97 <= b && b <= 122 || 65 <= b && b <= 90)
                return true;
            byte num = b;
            if (num <= 46U)
            {
                switch (num)
                {
                    case 33:
                    case 36:
                    case 38:
                    case 43:
                    case 45:
                    case 46:
                        break;
                    default:
                        goto label_6;
                }
            }
            else if (num != 58 && (int)num != 95 && (int)num != 126)
                goto label_6;
            return true;
            label_6:
            return false;
        }
    }
}