using System.Buffers.Binary;
using System.Net.Sockets;
using System.Text;

namespace Api.SeaHavenIndustries.Helper
{
    public enum DocumentScanResult
    {
        Passed,
        Infected,
        Unavailable
    }

    public interface IDocumentScanner
    {
        Task<DocumentScanResult> ScanAsync(string path, CancellationToken cancellationToken);
    }

    public class ClamAvDocumentScanner : IDocumentScanner
    {
        private readonly IConfiguration _configuration;

        public ClamAvDocumentScanner(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        public async Task<DocumentScanResult> ScanAsync(string path, CancellationToken cancellationToken)
        {
            var host = _configuration["ClamAV:Host"];
            var port = _configuration.GetValue<int?>("ClamAV:Port") ?? 3310;
            if (string.IsNullOrWhiteSpace(host) || !File.Exists(path))
                return DocumentScanResult.Unavailable;

            try
            {
                using var client = new TcpClient();
                await client.ConnectAsync(host, port, cancellationToken);
                await using var network = client.GetStream();
                await network.WriteAsync(Encoding.ASCII.GetBytes("zINSTREAM\0"), cancellationToken);
                await using var file = File.OpenRead(path);
                var buffer = new byte[64 * 1024];
                while (true)
                {
                    var count = await file.ReadAsync(buffer, cancellationToken);
                    if (count == 0) break;
                    var length = new byte[4];
                    BinaryPrimitives.WriteInt32BigEndian(length, count);
                    await network.WriteAsync(length, cancellationToken);
                    await network.WriteAsync(buffer.AsMemory(0, count), cancellationToken);
                }
                await network.WriteAsync(new byte[4], cancellationToken);
                await network.FlushAsync(cancellationToken);

                var responseBuffer = new byte[1024];
                var responseLength = await network.ReadAsync(responseBuffer, cancellationToken);
                var response = Encoding.ASCII.GetString(responseBuffer, 0, responseLength);
                if (response.Contains("FOUND", StringComparison.OrdinalIgnoreCase))
                    return DocumentScanResult.Infected;
                return response.Contains("OK", StringComparison.OrdinalIgnoreCase)
                    ? DocumentScanResult.Passed
                    : DocumentScanResult.Unavailable;
            }
            catch (Exception) when (!cancellationToken.IsCancellationRequested)
            {
                return DocumentScanResult.Unavailable;
            }
        }
    }
}