Create SerialDeviceMonitor.kt

Author: consuelita

Transmission/src/main/java/org/operatorfoundation/transmission/SerialDeviceMonitor.kt

@@ -0,0 +1,111 @@
+package org.operatorfoundation.transmission
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import android.hardware.usb.UsbManager
+import kotlinx.coroutines.flow.StateFlow
+import timber.log.Timber
+
+/**
+ * Application-scoped monitor for USB serial device availability.
+ *
+ * Wraps [SerialConnectionFactory] and self-registers a USB broadcast receiver
+ * using application context, so attach/detach events are handled for the full
+ * app lifetime without requiring any Activity involvement.
+ *
+ * Instantiate once in Application.onCreate() and hold as a property.
+ * Observe [connectionState] to react to connection changes.
+ *
+ * Usage:
+ * ```
+ * // In Application.onCreate():
+ * serialDeviceMonitor = SerialDeviceMonitor(applicationContext)
+ *
+ * // Anywhere that needs connection state:
+ * serialDeviceMonitor.connectionState.collect { state -> ... }
+ * ```
+ */
+class SerialDeviceMonitor(private val context: Context)
+{
+    private val factory = SerialConnectionFactory(context)
+
+    /** Current serial connection state. Observe this to react to connect/disconnect. */
+    val connectionState: StateFlow<SerialConnectionFactory.ConnectionState> = factory.connectionState
+
+    /** True when a serial connection is established. Convenience derived from [connectionState]. */
+    val isConnected: Boolean
+        get() = connectionState.value is SerialConnectionFactory.ConnectionState.Connected
+
+    // ==================== USB Broadcast Receiver ====================
+
+    private val usbReceiver = object : BroadcastReceiver()
+    {
+        override fun onReceive(context: Context, intent: Intent)
+        {
+            when (intent.action)
+            {
+                UsbManager.ACTION_USB_DEVICE_ATTACHED ->
+                {
+                    Timber.d("SerialDeviceMonitor: USB device attached")
+                    onDeviceAttached()
+                }
+
+                UsbManager.ACTION_USB_DEVICE_DETACHED ->
+                {
+                    Timber.d("SerialDeviceMonitor: USB device detached")
+                    factory.onDeviceDetached()
+                }
+            }
+        }
+    }
+
+    init
+    {
+        // Register receiver for the app's lifetime using application context.
+        // No need to unregister — this lives as long as the app does.
+        val filter = IntentFilter().apply {
+            addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED)
+            addAction(UsbManager.ACTION_USB_DEVICE_DETACHED)
+        }
+
+        context.registerReceiver(usbReceiver, filter, Context.RECEIVER_NOT_EXPORTED)
+        Timber.d("SerialDeviceMonitor: USB receiver registered")
+
+        // Check for already-connected devices on startup
+        // (device may have been attached before the app launched)
+        onDeviceAttached()
+    }
+
+    // ==================== Private ====================
+
+    /**
+     * Called on USB attach or startup. Finds available serial devices
+     * and initiates connection to the first one found, if any.
+     *
+     * No-ops if a connection is already established or in progress.
+     */
+    private fun onDeviceAttached()
+    {
+        // Don't attempt if already connected or connecting
+        val current = connectionState.value
+        if (current is SerialConnectionFactory.ConnectionState.Connected ||
+            current is SerialConnectionFactory.ConnectionState.Connecting ||
+            current is SerialConnectionFactory.ConnectionState.RequestingPermission)
+        {
+            Timber.d("SerialDeviceMonitor: connection already active, ignoring attach")
+            return
+        }
+
+        val devices = factory.findAvailableDevices()
+        if (devices.isEmpty())
+        {
+            Timber.d("SerialDeviceMonitor: no serial devices found")
+            return
+        }
+
+        Timber.d("SerialDeviceMonitor: found ${devices.size} device(s), connecting to first")
+        factory.createConnection(devices.first().device)
+    }
+}