Adding EthernetInterfaceTracker to support EthernetSettings

This class is part of the middleware and will be used to be notified
when an EthernetInterface is added or removed.

Flag: com.android.settings.connectivity.ethernet_settings

Test: atest
SettingsRoboTests: com.android.settings.network.EthernetInterfaceTrackerTest
Change-Id: If3a1f4d7a96b301cd47ffbea55864bcc780cd1e0

src/com/android/settings/network/ethernet/EthernetInterfaceTracker.kt

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.network.ethernet
+
+import android.content.Context
+import android.net.EthernetManager
+import android.net.IpConfiguration
+import androidx.core.content.ContextCompat
+import java.util.concurrent.Executor
+
+class EthernetInterfaceTracker(private val context: Context) :
+    EthernetManager.InterfaceStateListener {
+    interface EthernetInterfaceListListener {
+        fun onInterfaceListChanged()
+    }
+
+    private val ethernetManager =
+        context.getSystemService(Context.ETHERNET_SERVICE) as EthernetManager
+    private val TAG = "EthernetInterfaceTracker"
+
+    // Maps ethernet interface identifier to EthernetInterface object
+    private val ethernetInterfaces = mutableMapOf<String, EthernetInterface>()
+    private val interfaceListeners = mutableListOf<EthernetInterfaceListListener>()
+    private val mExecutor = ContextCompat.getMainExecutor(context)
+
+    init {
+        ethernetManager.addInterfaceStateListener(mExecutor, this)
+    }
+
+    fun getInterface(id: String): EthernetInterface? {
+        return ethernetInterfaces.get(id)
+    }
+
+    fun getAvailableInterfaces(): Collection<EthernetInterface> {
+        return ethernetInterfaces.values
+    }
+
+    fun registerInterfaceListener(listener: EthernetInterfaceListListener) {
+        interfaceListeners.add(listener)
+    }
+
+    fun unregisterInterfaceListener(listener: EthernetInterfaceListListener) {
+        interfaceListeners.remove(listener)
+    }
+
+    override fun onInterfaceStateChanged(id: String, state: Int, role: Int, cfg: IpConfiguration?) {
+        var interfacesChanged = false
+        if (!ethernetInterfaces.contains(id) && state != EthernetManager.STATE_ABSENT) {
+            ethernetInterfaces.put(id, EthernetInterface(context, id))
+            interfacesChanged = true
+        } else if (ethernetInterfaces.contains(id) && state == EthernetManager.STATE_ABSENT) {
+            ethernetInterfaces.remove(id)
+            interfacesChanged = true
+        }
+        if (interfacesChanged) {
+            for (listener in interfaceListeners) {
+                listener.onInterfaceListChanged()
+            }
+        }
+    }
+}