using System.Security.Cryptography;
using System.Text;
using Azaion.Common.Entities;

namespace Azaion.Services;

public static class Security
{
    private const int BUFFER_SIZE = 524288; // 512 KB buffer size

    public static string ToHash(this string str) =>
        Convert.ToBase64String(SHA384.HashData(Encoding.UTF8.GetBytes(str)));

    public static string GetHWHash(string hardware) =>
        $"Azaion_{hardware}_%$$$)0_".ToHash();

    public static string GetApiEncryptionKey(string email, string password, string? hardwareHash) =>
        $"{email}-{password}-{hardwareHash}-#%@AzaionKey@%#---".ToHash();

    public static async Task EncryptTo(this Stream inputStream, Stream toStream, string key, CancellationToken cancellationToken = default)
    {
        inputStream.Seek(0, SeekOrigin.Begin);
        if (inputStream is { CanRead: false }) throw new ArgumentNullException(nameof(inputStream));
        if (key is not { Length: > 0 }) throw new ArgumentNullException(nameof(key));

        using var aes = Aes.Create();
        aes.Mode = CipherMode.CBC;
        aes.Padding = PaddingMode.PKCS7;
        aes.Key = SHA256.HashData(Encoding.UTF8.GetBytes(key));
        aes.GenerateIV();
        using var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);

        await using var cs = new CryptoStream(toStream, encryptor, CryptoStreamMode.Write, leaveOpen: true);

        await toStream.WriteAsync(aes.IV.AsMemory(0, aes.IV.Length), cancellationToken);

        var buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        while ((bytesRead = await inputStream.ReadAsync(buffer, cancellationToken)) > 0)
            await cs.WriteAsync(buffer.AsMemory(0, bytesRead), cancellationToken);
    }

    public static async Task DecryptTo(this Stream encryptedStream, Stream toStream, string key, CancellationToken cancellationToken = default)
    {
        encryptedStream.Seek(0, SeekOrigin.Begin);
        using var aes = Aes.Create();
        aes.Key = SHA256.HashData(Encoding.UTF8.GetBytes(key));

        var iv = new byte[aes.BlockSize / 8];
        _ = await encryptedStream.ReadAsync(iv, cancellationToken);
        aes.IV = iv;
        aes.Mode = CipherMode.CBC;
        aes.Padding = PaddingMode.PKCS7;
        using var decryptor = aes.CreateDecryptor(aes.Key, aes.IV);

        await using var cryptoStream = new CryptoStream(encryptedStream, decryptor, CryptoStreamMode.Read, leaveOpen: true);

        var buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        while ((bytesRead = await cryptoStream.ReadAsync(buffer, cancellationToken)) > 0)
            await toStream.WriteAsync(buffer.AsMemory(0, bytesRead), cancellationToken);
        toStream.Seek(0, SeekOrigin.Begin);
    }
}