Add SFTP tools with SCP fallback

src/McpSsh.Server/Ssh/SshClientFactory.cs

@@ -0,0 +1,70 @@
+using Renci.SshNet;
+
+namespace McpSsh.Server.Ssh;
+
+public interface ISshClientFactory
+{
+    SshClient CreateSshClient(SshConnectionRequest request);
+
+    SftpClient CreateSftpClient(SshConnectionRequest request);
+
+    ScpClient CreateScpClient(SshConnectionRequest request);
+}
+
+public sealed record SshConnectionRequest(
+    string Host,
+    string Username,
+    int Port,
+    string? KeyPath,
+    string? KeyPassphrase,
+    TimeSpan? Timeout = null);
+
+public sealed class SshNetClientFactory : ISshClientFactory
+{
+    private readonly ISshKeyResolver _keyResolver;
+
+    public SshNetClientFactory(ISshKeyResolver keyResolver)
+    {
+        _keyResolver = keyResolver;
+    }
+
+    public SshClient CreateSshClient(SshConnectionRequest request)
+    {
+        var client = new SshClient(CreateConnectionInfo(request));
+        ApplyTimeout(client, request.Timeout);
+        return client;
+    }
+
+    public SftpClient CreateSftpClient(SshConnectionRequest request)
+    {
+        var client = new SftpClient(CreateConnectionInfo(request));
+        ApplyTimeout(client, request.Timeout);
+        return client;
+    }
+
+    public ScpClient CreateScpClient(SshConnectionRequest request)
+    {
+        var client = new ScpClient(CreateConnectionInfo(request));
+        ApplyTimeout(client, request.Timeout);
+        return client;
+    }
+
+    private ConnectionInfo CreateConnectionInfo(SshConnectionRequest request)
+    {
+        var keyPath = _keyResolver.ResolveKeyPath(request.KeyPath);
+        var keyFile = string.IsNullOrEmpty(request.KeyPassphrase)
+            ? new PrivateKeyFile(keyPath)
+            : new PrivateKeyFile(keyPath, request.KeyPassphrase);
+
+        var auth = new PrivateKeyAuthenticationMethod(request.Username, keyFile);
+        return new ConnectionInfo(request.Host, request.Port, request.Username, auth);
+    }
+
+    private static void ApplyTimeout(BaseClient client, TimeSpan? timeout)
+    {
+        if (timeout is { } value)
+        {
+            client.ConnectionInfo.Timeout = value;
+        }
+    }
+}