Add battery chart view model.

Test: manual
Bug: 239491373
Bug: 236101166
Change-Id: I1ae0e5fcc006855ac552fbbdfb4cd73f3dec52e7

src/com/android/settings/fuelgauge/batteryusage/BatteryChartViewModel.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2022 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.fuelgauge.batteryusage;
+
+import androidx.annotation.NonNull;
+import androidx.core.util.Preconditions;
+
+import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
+
+/** The view model of {@code BatteryChartViewV2} */
+class BatteryChartViewModel {
+    private static final String TAG = "BatteryChartViewModel";
+
+    public static final int SELECTED_INDEX_ALL = -1;
+    public static final int SELECTED_INDEX_INVALID = -2;
+
+    // We need at least 2 levels to draw a trapezoid.
+    private static final int MIN_LEVELS_DATA_SIZE = 2;
+
+    private final List<Integer> mLevels;
+    private final List<String> mTexts;
+    private int mSelectedIndex;
+
+    BatteryChartViewModel(
+            @NonNull List<Integer> levels, @NonNull List<String> texts, int selectedIndex) {
+        Preconditions.checkArgument(
+                levels.size() == texts.size()
+                        && levels.size() >= MIN_LEVELS_DATA_SIZE
+                        && selectedIndex >= SELECTED_INDEX_ALL
+                        && selectedIndex < levels.size(),
+                String.format(Locale.getDefault(), "Invalid BatteryChartViewModel"
+                                + "  levels.size: %d\ntexts.size: %d\nselectedIndex: %d.",
+                        levels.size(), texts.size(), selectedIndex));
+        mLevels = levels;
+        mTexts = texts;
+        mSelectedIndex = selectedIndex;
+    }
+
+    public int size() {
+        return mLevels.size();
+    }
+
+    public List<Integer> levels() {
+        return mLevels;
+    }
+
+    public List<String> texts() {
+        return mTexts;
+    }
+
+    public int selectedIndex() {
+        return mSelectedIndex;
+    }
+
+    public void setSelectedIndex(int index) {
+        mSelectedIndex = index;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(mLevels, mTexts, mSelectedIndex);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (this == other) {
+            return true;
+        } else if (!(other instanceof BatteryChartViewModel)) {
+            return false;
+        }
+        final BatteryChartViewModel batteryChartViewModel = (BatteryChartViewModel) other;
+        return Objects.equals(mLevels, batteryChartViewModel.mLevels)
+                && Objects.equals(mTexts, batteryChartViewModel.mTexts)
+                && mSelectedIndex == batteryChartViewModel.mSelectedIndex;
+    }
+
+    @Override
+    public String toString() {
+        return String.format(Locale.getDefault(), "levels: %s\ntexts: %s\nselectedIndex: %d",
+                Objects.toString(mLevels), Objects.toString(mTexts), mSelectedIndex);
+    }
+}