using ICSharpCode.SharpZipLib.GZip;
using System.IO.Compression;
using System.Security.Cryptography;
using System.Text;

namespace Elisa.WebAPI.Utils;

public static class Crypto
{
    static DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    static MD5 md5 = System.Security.Cryptography.MD5.Create();

    public static string Decrypt(string body, string key)
    {
        if (string.IsNullOrEmpty(body) || string.IsNullOrEmpty(key))
            return string.Empty;

        if (body.Length == 1 || body.StartsWith("error:") || (body.StartsWith("{") && body.EndsWith("}")))
            return body;

        try
        {
            string text = MD5(MD5(key).Substring(16));
            string pwd = text + MD5(text);

            if (body.StartsWith("#"))
            {
                body = body.Substring(1);

                return GZipDecompress(RC4(ConvertFromBase64String(body), pwd).Skip(26).ToArray<byte>());
            }

            byte[] bytes = RC4(ConvertFromBase64String(body), pwd);
            string @string = Encoding.UTF8.GetString(bytes);

            return (@string.Length > 26) ? @string.Substring(26) : string.Empty;
        }
        catch
        {
        }

        return string.Empty;
    }

    public static string Encrypt(string body, string key)
    {
        try
        {
            byte[] array = GZipCompress(Encoding.UTF8.GetBytes(body));
            string text = MD5(key);
            string s = MD5(text.Substring(0, 16));
            string text2 = MD5(text.Substring(16, 16));
            string pwd = text2 + MD5(text2);
            byte[] bytes = Encoding.UTF8.GetBytes(string.Format("{0}", Math.Round(GetCurrentSec()) + 3600.0));
            string s2 = MD5(array.Concat(Encoding.UTF8.GetBytes(s)).ToArray<byte>()).Substring(0, 16);
            byte[] array2 = new byte[array.Length + 26];

            Array.Copy(bytes, 0, array2, 0, bytes.Length);
            Array.Copy(Encoding.UTF8.GetBytes(s2), 0, array2, 10, 16);
            Array.Copy(array, 0, array2, 26, array.Length);

            return "#" + Convert.ToBase64String(RC4(array2, pwd));
        }
        catch
        {
        }

        return string.Empty;
    }

    public static byte[] ConvertFromBase64String(string input)
    {
        byte[] result = [];

        try
        {
            result = Convert.FromBase64String(input);
        }
        catch
        {
            try
            {
                result = Convert.FromBase64String(input + "=");
            }
            catch
            {
                try
                {
                    result = Convert.FromBase64String(input + "==");
                }
                catch
                {
                    return result;
                }
            }
        }

        return result;
    }

    public static double GetCurrentSec()
    {
        return (DateTime.UtcNow - epoch).TotalSeconds;
    }

    public static string MD5(string input)
    {
        return MD5(Encoding.UTF8.GetBytes(input));
    }

    public static string MD5(byte[] input)
    {
        byte[] array = md5.ComputeHash(input);
        StringBuilder stringBuilder = new StringBuilder();

        for (int i = 0; i < array.Length; i++)
            stringBuilder.Append(array[i].ToString("x2"));

        return stringBuilder.ToString();
    }

    public static byte[] RC4(byte[] data, string pwd)
    {
        return RC4(data, Encoding.UTF8.GetBytes(pwd));
    }

    public static byte[] RC4(byte[] data, byte[] pwd)
    {
        int[] array = new int[256];
        int[] array2 = new int[256];
        byte[] array3 = new byte[data.Length];
        int i;
        int num;

        for (i = 0; i < 256; i++)
        {
            array[i] = (int)pwd[i % pwd.Length];
            array2[i] = i;
        }

        for (i = (num = 0); i < 256; i++)
        {
            int num2 = array2[i];

            num = (num + array2[i] + array[i]) % 256;
            array2[i] = array2[num];
            array2[num] = num2;
        }

        int num3;
        num = (num3 = (i = 0));

        while (i < data.Length)
        {
            num3++;
            num3 %= 256;
            num += array2[num3];
            num %= 256;

            int num2 = array2[num3];
            array2[num3] = array2[num];
            array2[num] = num2;

            int num4 = array2[(array2[num3] + array2[num]) % 256];
            array3[i] = (byte)((int)data[i] ^ num4);

            i++;
        }

        return array3;
    }

    public static byte[] GZipCompress(byte[] raw)
    {
        byte[] result;

        using (MemoryStream memoryStream = new MemoryStream())
        {
            using GZipOutputStream gzipOutputStream = new GZipOutputStream(memoryStream);

            gzipOutputStream.IsStreamOwner = false;
            gzipOutputStream.Write(raw, 0, raw.Length);
            gzipOutputStream.Flush();
            gzipOutputStream.Finish();

            result = memoryStream.ToArray();
        }

        return result;
    }

    public static string GZipDecompress(byte[] raw)
    {
        string result;

        using (MemoryStream memoryStream = new MemoryStream(raw))
        {
            using Stream stream = new GZipInputStream(memoryStream);
            using StreamReader streamReader = new StreamReader(stream, Encoding.UTF8);

            result = streamReader.ReadToEnd();
        }

        return result;
    }

    public static string CompressText(string text)
    {
        byte[] bytes = Encoding.UTF8.GetBytes(text);
        byte[]? inArray = null;

        using (MemoryStream memoryStream = new MemoryStream())
        {
            using (GZipStream gzipStream = new GZipStream(memoryStream, CompressionMode.Compress))
            {
                gzipStream.Write(bytes, 0, bytes.Length);
            }

            inArray = memoryStream.ToArray();
        }

        return Convert.ToBase64String(inArray);
    }

    public static string DecompressText(string text)
    {
        string result = string.Empty;

        using (MemoryStream memoryStream = new MemoryStream(Convert.FromBase64String(text)))
        {
            using (GZipStream gzipStream = new GZipStream(memoryStream, CompressionMode.Decompress))
            {
                using (StreamReader streamReader = new StreamReader(gzipStream))
                {
                    result = streamReader.ReadToEnd();
                }
            }
        }

        return result;
    }

    public static string ConvertMD5(string input)
    {
        byte[] array = md5.ComputeHash(Encoding.UTF8.GetBytes(input));
        StringBuilder stringBuilder = new StringBuilder();

        for (int i = 0; i < array.Length; i++)
            stringBuilder.Append(array[i].ToString("x2"));

        return stringBuilder.ToString();
    }
}