From 1d90bf3611d54cb60b931286798e42533bf0e96f Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Fri, 24 Jul 2026 14:08:10 -0400
Subject: [PATCH] feat(modbus-rtu): add ModbusTransportFactory switch on
 Transport mode

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW
---
 .../ModbusTransportFactory.cs                 | 37 +++++++++++++++++++
 .../ModbusTransportFactoryTests.cs            | 22 +++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportFactory.cs
 create mode 100644 tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusTransportFactoryTests.cs

diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportFactory.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportFactory.cs
new file mode 100644
index 00000000..88827a8e
--- /dev/null
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusTransportFactory.cs
@@ -0,0 +1,37 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
+
+/// <summary>
+///     Single mapping point from <see cref="ModbusDriverOptions"/> to the concrete
+///     <see cref="IModbusTransport"/> its <see cref="ModbusDriverOptions.Transport"/> selects.
+///     Consumed by both <see cref="ModbusDriver"/>'s default transport-factory closure and the
+///     AdminUI Test-Connect probe, so the <see cref="ModbusTransportMode"/> switch lives in
+///     exactly one place.
+/// </summary>
+public static class ModbusTransportFactory
+{
+    /// <summary>
+    ///     Builds the transport <paramref name="options"/>.<see cref="ModbusDriverOptions.Transport"/>
+    ///     selects, threading every shared connection setting (Host/Port/Timeout/AutoReconnect/
+    ///     KeepAlive/IdleDisconnectTimeout/Reconnect) through to whichever concrete transport is built.
+    /// </summary>
+    /// <param name="options">Driver configuration options.</param>
+    /// <returns>A <see cref="ModbusRtuOverTcpTransport"/> when <see cref="ModbusTransportMode.RtuOverTcp"/>
+    /// is selected; otherwise a <see cref="ModbusTcpTransport"/> (also the default/unrecognized fallback).</returns>
+    public static IModbusTransport Create(ModbusDriverOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+        return options.Transport switch
+        {
+            ModbusTransportMode.RtuOverTcp => new ModbusRtuOverTcpTransport(
+                options.Host, options.Port, options.Timeout, options.AutoReconnect,
+                keepAlive: options.KeepAlive,
+                idleDisconnect: options.IdleDisconnectTimeout,
+                reconnect: options.Reconnect),
+            _ => new ModbusTcpTransport(
+                options.Host, options.Port, options.Timeout, options.AutoReconnect,
+                keepAlive: options.KeepAlive,
+                idleDisconnect: options.IdleDisconnectTimeout,
+                reconnect: options.Reconnect),
+        };
+    }
+}
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusTransportFactoryTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusTransportFactoryTests.cs
new file mode 100644
index 00000000..5644998f
--- /dev/null
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests/ModbusTransportFactoryTests.cs
@@ -0,0 +1,22 @@
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Tests;
+
+public sealed class ModbusTransportFactoryTests
+{
+    [Fact]
+    public void Tcp_mode_builds_tcp_transport()
+        => ModbusTransportFactory.Create(new ModbusDriverOptions { Transport = ModbusTransportMode.Tcp })
+            .ShouldBeOfType<ModbusTcpTransport>();
+
+    [Fact]
+    public void RtuOverTcp_mode_builds_rtu_transport()
+        => ModbusTransportFactory.Create(new ModbusDriverOptions { Transport = ModbusTransportMode.RtuOverTcp })
+            .ShouldBeOfType<ModbusRtuOverTcpTransport>();
+
+    [Fact]
+    public void Default_options_build_tcp_transport()
+        => ModbusTransportFactory.Create(new ModbusDriverOptions())
+            .ShouldBeOfType<ModbusTcpTransport>();
+}