using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Runtime.Intrinsics.X86;
using System.Security.Cryptography;
using System.Text;

namespace SunlightAggregationManager.UserClass
{
    public class AES
    {
        public static string AesEncipher(string Key, string dat) //加密
        {
            //压缩
            byte[] plainBytes = Compress( Encoding.UTF8.GetBytes(dat));

            using var sha256 = System.Security.Cryptography.SHA256.Create();
            using var aes = System.Security.Cryptography.Aes.Create();

            aes.Key = sha256.ComputeHash(Encoding.UTF8.GetBytes(Key));
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;
            aes.GenerateIV(); // 生成随机 IV

            using var enc = aes.CreateEncryptor();
            byte[] cipherBytes = enc.TransformFinalBlock(plainBytes, 0, plainBytes.Length);

            //将 IV (16字节) 和 密文 拼接成一个完整的字节数组
            byte[] combinedBytes = new byte[aes.IV.Length + cipherBytes.Length];
            Buffer.BlockCopy(aes.IV, 0, combinedBytes, 0, aes.IV.Length);
            Buffer.BlockCopy(cipherBytes, 0, combinedBytes, aes.IV.Length, cipherBytes.Length);

            return Convert.ToBase64String(combinedBytes);
        }

        public static string AesDecrypt(string Key, string dat)//解密
        {
            // 解码Base64
            byte[] cipherBytes = Convert.FromBase64String(dat);

            using var sha256 = System.Security.Cryptography.SHA256.Create();
            using var aes = System.Security.Cryptography.Aes.Create();

            aes.Key = sha256.ComputeHash(Encoding.UTF8.GetBytes(Key));
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;
            // 从字节数组中提取前 16 字节作为 IV
            aes.IV = cipherBytes.AsSpan(0, 16).ToArray();
            using var dec = aes.CreateDecryptor();

            // 解密
            byte[] bytes = dec.TransformFinalBlock(cipherBytes, 16, cipherBytes.Length - 16);
            //解压缩并返回
            return Encoding.UTF8.GetString(Decompress(bytes));
        }

        // 3. Brotli 压缩辅助方法
        private static byte[] Compress(byte[] data)
        {
            using var output = new MemoryStream();
            using (var brotli = new BrotliStream(output, CompressionLevel.Optimal))
            {
                brotli.Write(data, 0, data.Length);
            }
            return output.ToArray();
        }

        // 4. Brotli 解压辅助方法
        private static byte[] Decompress(byte[] data)
        {
            using var input = new MemoryStream(data);
            using var brotli = new BrotliStream(input, CompressionMode.Decompress);
            using var output = new MemoryStream();
            brotli.CopyTo(output);
            return output.ToArray();
        }
    }
}