using Renci.SshNet;
using Renci.SshNet.Common;
using McpSsh.Server.Ssh;

namespace McpSsh.Server.Terminal;

public interface ITerminalConnection : IDisposable
{
    bool DataAvailable { get; }

    string ReadAvailable();

    void Write(string input);
}

public interface ITerminalConnectionFactory
{
    ITerminalConnection Create(TerminalStartRequest request);
}

public sealed class SshNetTerminalConnectionFactory : ITerminalConnectionFactory
{
    private const int ShellBufferSize = 16 * 1024;
    private readonly ISshKeyResolver _keyResolver;

    public SshNetTerminalConnectionFactory(ISshKeyResolver keyResolver)
    {
        _keyResolver = keyResolver;
    }

    public ITerminalConnection Create(TerminalStartRequest request)
    {
        try
        {
            var keyPath = _keyResolver.ResolveKeyPath(request.KeyPath);
            var keyFile = string.IsNullOrEmpty(request.KeyPassphrase)
                ? new PrivateKeyFile(keyPath)
                : new PrivateKeyFile(keyPath, request.KeyPassphrase);
            var client = new SshClient(request.Host, request.Port, request.Username, keyFile);

            client.Connect();

            var stream = client.CreateShellStream(
                "xterm-256color",
                (uint)request.Cols,
                (uint)request.Rows,
                width: 0,
                height: 0,
                bufferSize: ShellBufferSize);

            return new SshNetTerminalConnection(client, stream, keyFile);
        }
        catch (SshAuthenticationException ex)
        {
            throw new SshToolException("ssh_authentication_failed", "SSH key authentication failed. Check the username, key path, and key passphrase.", ex);
        }
        catch (SshException ex)
        {
            throw new SshToolException("ssh_error", ex.Message, ex);
        }
    }

    private sealed class SshNetTerminalConnection : ITerminalConnection
    {
        private readonly SshClient _client;
        private readonly ShellStream _stream;
        private readonly PrivateKeyFile _keyFile;

        public SshNetTerminalConnection(SshClient client, ShellStream stream, PrivateKeyFile keyFile)
        {
            _client = client;
            _stream = stream;
            _keyFile = keyFile;
        }

        public bool DataAvailable => _stream.DataAvailable;

        public string ReadAvailable()
        {
            return _stream.Read();
        }

        public void Write(string input)
        {
            _stream.Write(input);
        }

        public void Dispose()
        {
            _stream.Dispose();
            _client.Dispose();
            _keyFile.Dispose();
        }
    }
}