Refer to the last Hotspot password when generating the password

- Query the last Hotspot password when security type is SECURITY_TYPE_OPEN and it will be used when the user changes to another security type

- If the last hotspot password is an empty string, then generate random password

Bug: 201789473
Test: manual test
atest -c WifiHotspotRepositoryTest
make RunSettingsRoboTests ROBOTEST_FILTER=WifiTetherPasswordPreferenceControllerTest

Change-Id: Id3a846099238433e7b6c8b934fa26a74df0dcb61

src/com/android/settings/wifi/repository/WifiHotspotRepository.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2023 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.wifi.repository;
+
+import android.content.Context;
+import android.net.wifi.SoftApConfiguration;
+import android.net.wifi.WifiManager;
+import android.text.TextUtils;
+
+import androidx.annotation.NonNull;
+
+import java.util.UUID;
+import java.util.function.Consumer;
+
+/**
+ * Wi-Fi Hotspot Repository
+ */
+public class WifiHotspotRepository {
+
+    protected final Context mAppContext;
+    protected final WifiManager mWifiManager;
+
+    protected String mLastPassword;
+    protected LastPasswordListener mLastPasswordListener = new LastPasswordListener();
+
+    public WifiHotspotRepository(@NonNull Context appContext, @NonNull WifiManager wifiManager) {
+        mAppContext = appContext;
+        mWifiManager = wifiManager;
+    }
+
+    /**
+     * Query the last configured Tethered Ap Passphrase since boot.
+     */
+    public void queryLastPasswordIfNeeded() {
+        SoftApConfiguration config = mWifiManager.getSoftApConfiguration();
+        if (config.getSecurityType() != SoftApConfiguration.SECURITY_TYPE_OPEN) {
+            return;
+        }
+        mWifiManager.queryLastConfiguredTetheredApPassphraseSinceBoot(mAppContext.getMainExecutor(),
+                mLastPasswordListener);
+    }
+
+    /**
+     * Generate password.
+     */
+    public String generatePassword() {
+        return !TextUtils.isEmpty(mLastPassword) ? mLastPassword : generateRandomPassword();
+    }
+
+    private class LastPasswordListener implements Consumer<String> {
+        @Override
+        public void accept(String password) {
+            mLastPassword = password;
+        }
+    }
+
+    private static String generateRandomPassword() {
+        String randomUUID = UUID.randomUUID().toString();
+        //first 12 chars from xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
+        return randomUUID.substring(0, 8) + randomUUID.substring(9, 13);
+    }
+}