Extract and refactor logic to determine the data usage summary mark.

Created a new controller for DataUsageInfo and add appropriate
unit tests.

Bug: 30946416
Change-Id: Ida1281a771013fd807242f846edb4f2a9c0ccabb
Test: Robolectric tests with target RunSettingsRoboTests

src/com/android/settings/datausage/DataUsageInfoController.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2016 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.datausage;
+
+import android.net.NetworkPolicy;
+import com.android.settingslib.net.DataUsageController.DataUsageInfo;
+
+/**
+ * Controller to handle caching and mobile data logic.
+ */
+public class DataUsageInfoController {
+    /**
+     * Take the cached data usage values in the NetworkPolicy to update DataUsageInfo.
+     */
+    public void updateDataLimit(DataUsageInfo info, NetworkPolicy policy) {
+        if (info == null || policy == null) {
+            return;
+        }
+        if (policy.warningBytes >= 0) {
+            info.warningLevel = policy.warningBytes;
+        }
+        if (policy.limitBytes >= 0) {
+            info.limitLevel = policy.limitBytes;
+        }
+    }
+
+    /**
+     * @returns the most appropriate limit for the data usage summary. Use the total usage when it
+     * is higher than the limit and warning level. Use the limit when it is set and less than usage.
+     * Otherwise use warning level.
+     */
+    public long getSummaryLimit(DataUsageInfo info) {
+        long limit = info.limitLevel;
+        if (limit <= 0) {
+            limit = info.warningLevel;
+        }
+        if (info.usageLevel > limit) {
+            limit = info.usageLevel;
+        }
+        return limit;
+    }
+}