fuelgauge/batteryusage/DataProcessor.java

/*
 * 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 static com.android.settings.fuelgauge.batteryusage.ConvertUtils.utcToLocalTime;

import android.app.settings.SettingsEnums;
import android.content.ContentValues;
import android.content.Context;
import android.os.AsyncTask;
import android.os.BatteryStatsManager;
import android.os.BatteryUsageStats;
import android.os.BatteryUsageStatsQuery;
import android.os.Handler;
import android.os.Looper;
import android.os.UserHandle;
import android.os.UserManager;
import android.text.TextUtils;
import android.text.format.DateUtils;
import android.util.ArraySet;
import android.util.Log;

import androidx.annotation.Nullable;

import com.android.internal.annotations.VisibleForTesting;
import com.android.settings.Utils;
import com.android.settings.fuelgauge.BatteryUtils;
import com.android.settings.overlay.FeatureFactory;
import com.android.settingslib.core.instrumentation.MetricsFeatureProvider;
import com.android.settingslib.fuelgauge.BatteryStatus;

import java.time.Duration;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

/**
 * A utility class to process data loaded from database and make the data easy to use for battery
 * usage UI.
 */
public final class DataProcessor {
    private static final boolean DEBUG = false;
    private static final String TAG = "DataProcessor";
    private static final int MIN_DAILY_DATA_SIZE = 2;
    private static final int MIN_TIMESTAMP_DATA_SIZE = 2;
    private static final int MAX_DIFF_SECONDS_OF_UPPER_TIMESTAMP = 5;
    // Maximum total time value for each hourly slot cumulative data at most 2 hours.
    private static final float TOTAL_HOURLY_TIME_THRESHOLD = DateUtils.HOUR_IN_MILLIS * 2;
    private static final long MIN_TIME_SLOT = DateUtils.HOUR_IN_MILLIS * 2;
    private static final Map<String, BatteryHistEntry> EMPTY_BATTERY_MAP = new HashMap<>();
    private static final BatteryHistEntry EMPTY_BATTERY_HIST_ENTRY =
            new BatteryHistEntry(new ContentValues());

    @VisibleForTesting
    static final double PERCENTAGE_OF_TOTAL_THRESHOLD = 1f;
    @VisibleForTesting
    static final int SELECTED_INDEX_ALL = BatteryChartViewModel.SELECTED_INDEX_ALL;

    /** A fake package name to represent no BatteryEntry data. */
    public static final String FAKE_PACKAGE_NAME = "fake_package";

    /** A callback listener when battery usage loading async task is executed. */
    public interface UsageMapAsyncResponse {
        /** The callback function when batteryUsageMap is loaded. */
        void onBatteryUsageMapLoaded(
                Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap);
    }

    private DataProcessor() {
    }

    /**
     * @return Returns battery level data and start async task to compute battery diff usage data
     * and load app labels + icons.
     * Returns null if the input is invalid or not having at least 2 hours data.
     */
    @Nullable
    public static BatteryLevelData getBatteryLevelData(
            Context context,
            @Nullable Handler handler,
            @Nullable final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap,
            final UsageMapAsyncResponse asyncResponseDelegate) {
        if (batteryHistoryMap == null || batteryHistoryMap.isEmpty()) {
            Log.d(TAG, "batteryHistoryMap is null in getBatteryLevelData()");
            loadBatteryUsageDataFromBatteryStatsService(
                    context, handler, asyncResponseDelegate);
            return null;
        }
        handler = handler != null ? handler : new Handler(Looper.getMainLooper());
        // Process raw history map data into hourly timestamps.
        final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap =
                getHistoryMapWithExpectedTimestamps(context, batteryHistoryMap);
        // Wrap and processed history map into easy-to-use format for UI rendering.
        final BatteryLevelData batteryLevelData =
                getLevelDataThroughProcessedHistoryMap(context, processedBatteryHistoryMap);
        if (batteryLevelData == null) {
            loadBatteryUsageDataFromBatteryStatsService(
                    context, handler, asyncResponseDelegate);
            Log.d(TAG, "getBatteryLevelData() returns null");
            return null;
        }

        // Start the async task to compute diff usage data and load labels and icons.
        new ComputeUsageMapAndLoadItemsTask(
                context,
                handler,
                asyncResponseDelegate,
                batteryLevelData.getHourlyBatteryLevelsPerDay(),
                processedBatteryHistoryMap).execute();

        return batteryLevelData;
    }

    /**
     * @return Returns battery usage data of different entries.
     * Returns null if the input is invalid or there is no enough data.
     */
    @Nullable
    public static Map<Integer, Map<Integer, BatteryDiffData>> getBatteryUsageData(
            Context context,
            @Nullable final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
        if (batteryHistoryMap == null || batteryHistoryMap.isEmpty()) {
            Log.d(TAG, "getBatteryLevelData() returns null");
            return null;
        }
        // Process raw history map data into hourly timestamps.
        final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap =
                getHistoryMapWithExpectedTimestamps(context, batteryHistoryMap);
        // Wrap and processed history map into easy-to-use format for UI rendering.
        final BatteryLevelData batteryLevelData =
                getLevelDataThroughProcessedHistoryMap(context, processedBatteryHistoryMap);
        return batteryLevelData == null
                ? null
                : getBatteryUsageMap(
                        context,
                        batteryLevelData.getHourlyBatteryLevelsPerDay(),
                        processedBatteryHistoryMap);
    }

    /**
     * @return Returns whether the target is in the CharSequence array.
     */
    public static boolean contains(String target, CharSequence[] packageNames) {
        if (target != null && packageNames != null) {
            for (CharSequence packageName : packageNames) {
                if (TextUtils.equals(target, packageName)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * @return Returns the processed history map which has interpolated to every hour data.
     * The start and end timestamp must be the even hours.
     * The keys of processed history map should contain every hour between the start and end
     * timestamp. If there's no data in some key, the value will be the empty hashmap.
     */
    @VisibleForTesting
    static Map<Long, Map<String, BatteryHistEntry>> getHistoryMapWithExpectedTimestamps(
            Context context,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
        final long startTime = System.currentTimeMillis();
        final List<Long> rawTimestampList = new ArrayList<>(batteryHistoryMap.keySet());
        final Map<Long, Map<String, BatteryHistEntry>> resultMap = new HashMap();
        if (rawTimestampList.isEmpty()) {
            Log.d(TAG, "empty batteryHistoryMap in getHistoryMapWithExpectedTimestamps()");
            return resultMap;
        }
        Collections.sort(rawTimestampList);
        final List<Long> expectedTimestampList = getTimestampSlots(rawTimestampList);
        final boolean isFromFullCharge =
                isFromFullCharge(batteryHistoryMap.get(rawTimestampList.get(0)));
        interpolateHistory(
                context, rawTimestampList, expectedTimestampList, isFromFullCharge,
                batteryHistoryMap, resultMap);
        Log.d(TAG, String.format("getHistoryMapWithExpectedTimestamps() size=%d in %d/ms",
                resultMap.size(), (System.currentTimeMillis() - startTime)));
        return resultMap;
    }

    @VisibleForTesting
    @Nullable
    static BatteryLevelData getLevelDataThroughProcessedHistoryMap(
            Context context,
            final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap) {
        final List<Long> timestampList = new ArrayList<>(processedBatteryHistoryMap.keySet());
        Collections.sort(timestampList);
        final List<Long> dailyTimestamps = getDailyTimestamps(timestampList);
        // There should be at least the start and end timestamps. Otherwise, return null to not show
        // data in usage chart.
        if (dailyTimestamps.size() < MIN_DAILY_DATA_SIZE) {
            return null;
        }

        final List<List<Long>> hourlyTimestamps = getHourlyTimestamps(dailyTimestamps);
        final BatteryLevelData.PeriodBatteryLevelData dailyLevelData =
                getPeriodBatteryLevelData(context, processedBatteryHistoryMap, dailyTimestamps);
        final List<BatteryLevelData.PeriodBatteryLevelData> hourlyLevelData =
                getHourlyPeriodBatteryLevelData(
                        context, processedBatteryHistoryMap, hourlyTimestamps);
        return new BatteryLevelData(dailyLevelData, hourlyLevelData);
    }

    /**
     * Computes expected timestamp slots for last full charge, which will return hourly timestamps
     * between start and end two even hour values.
     */
    @VisibleForTesting
    static List<Long> getTimestampSlots(final List<Long> rawTimestampList) {
        final List<Long> timestampSlots = new ArrayList<>();
        final int rawTimestampListSize = rawTimestampList.size();
        // If timestamp number is smaller than 2, the following computation is not necessary.
        if (rawTimestampListSize < MIN_TIMESTAMP_DATA_SIZE) {
            return timestampSlots;
        }
        final long rawStartTimestamp = rawTimestampList.get(0);
        final long rawEndTimestamp = rawTimestampList.get(rawTimestampListSize - 1);
        // No matter the start is from last full charge or 6 days ago, use the nearest even hour.
        final long startTimestamp = getNearestEvenHourTimestamp(rawStartTimestamp);
        // Use the even hour before the raw end timestamp as the end.
        final long endTimestamp = getLastEvenHourBeforeTimestamp(rawEndTimestamp);
        // If the start timestamp is later or equal the end one, return the empty list.
        if (startTimestamp >= endTimestamp) {
            return timestampSlots;
        }
        for (long timestamp = startTimestamp; timestamp <= endTimestamp;
                timestamp += DateUtils.HOUR_IN_MILLIS) {
            timestampSlots.add(timestamp);
        }
        return timestampSlots;
    }

    /**
     * Computes expected daily timestamp slots.
     *
     * The valid result should be composed of 3 parts:
     * 1) start timestamp
     * 2) every 00:00 timestamp (default timezone) between the start and end
     * 3) end timestamp
     * Otherwise, returns an empty list.
     */
    @VisibleForTesting
    static List<Long> getDailyTimestamps(final List<Long> timestampList) {
        final List<Long> dailyTimestampList = new ArrayList<>();
        // If timestamp number is smaller than 2, the following computation is not necessary.
        if (timestampList.size() < MIN_TIMESTAMP_DATA_SIZE) {
            return dailyTimestampList;
        }
        final long startTime = timestampList.get(0);
        final long endTime = timestampList.get(timestampList.size() - 1);
        // If the timestamp diff is smaller than MIN_TIME_SLOT, returns the empty list directly.
        if (endTime - startTime < MIN_TIME_SLOT) {
            return dailyTimestampList;
        }
        long nextDay = getTimestampOfNextDay(startTime);
        // Only if the timestamp diff in the first day is bigger than MIN_TIME_SLOT, start from the
        // first day. Otherwise, start from the second day.
        if (nextDay - startTime >= MIN_TIME_SLOT) {
            dailyTimestampList.add(startTime);
        }
        while (nextDay < endTime) {
            dailyTimestampList.add(nextDay);
            nextDay += DateUtils.DAY_IN_MILLIS;
        }
        final long lastDailyTimestamp = dailyTimestampList.get(dailyTimestampList.size() - 1);
        // Only if the timestamp diff in the last day is bigger than MIN_TIME_SLOT, add the
        // last day.
        if (endTime - lastDailyTimestamp >= MIN_TIME_SLOT) {
            dailyTimestampList.add(endTime);
        }
        // The dailyTimestampList must have the start and end timestamp, otherwise, return an empty
        // list.
        if (dailyTimestampList.size() < MIN_TIMESTAMP_DATA_SIZE) {
            return new ArrayList<>();
        }
        return dailyTimestampList;
    }

    @VisibleForTesting
    static boolean isFromFullCharge(@Nullable final Map<String, BatteryHistEntry> entryList) {
        if (entryList == null) {
            Log.d(TAG, "entryList is null in isFromFullCharge()");
            return false;
        }
        final List<String> entryKeys = new ArrayList<>(entryList.keySet());
        if (entryKeys.isEmpty()) {
            Log.d(TAG, "empty entryList in isFromFullCharge()");
            return false;
        }
        // The hist entries in the same timestamp should have same battery status and level.
        // Checking the first one should be enough.
        final BatteryHistEntry firstHistEntry = entryList.get(entryKeys.get(0));
        return BatteryStatus.isCharged(firstHistEntry.mBatteryStatus, firstHistEntry.mBatteryLevel);
    }

    @VisibleForTesting
    static long[] findNearestTimestamp(final List<Long> timestamps, final long target) {
        final long[] results = new long[] {Long.MIN_VALUE, Long.MAX_VALUE};
        // Searches the nearest lower and upper timestamp value.
        timestamps.forEach(timestamp -> {
            if (timestamp <= target && timestamp > results[0]) {
                results[0] = timestamp;
            }
            if (timestamp >= target && timestamp < results[1]) {
                results[1] = timestamp;
            }
        });
        // Uses zero value to represent invalid searching result.
        results[0] = results[0] == Long.MIN_VALUE ? 0 : results[0];
        results[1] = results[1] == Long.MAX_VALUE ? 0 : results[1];
        return results;
    }

    /**
     * @return Returns the timestamp for 00:00 1 day after the given timestamp based on local
     * timezone.
     */
    @VisibleForTesting
    static long getTimestampOfNextDay(long timestamp) {
        return getTimestampWithDayDiff(timestamp, /*dayDiff=*/ 1);
    }

    /**
     *  Returns whether currentSlot will be used in daily chart.
     */
    @VisibleForTesting
    static boolean isForDailyChart(final boolean isStartOrEnd, final long currentSlot) {
        // The start and end timestamps will always be used in daily chart.
        if (isStartOrEnd) {
            return true;
        }

        // The timestamps for 00:00 will be used in daily chart.
        final long startOfTheDay = getTimestampWithDayDiff(currentSlot, /*dayDiff=*/ 0);
        return currentSlot == startOfTheDay;
    }

    /**
     * @return Returns the indexed battery usage data for each corresponding time slot.
     *
     * There could be 2 cases of the returned value:
     * 1) null: empty or invalid data.
     * 2) non-null: must be a 2d map and composed by 3 parts:
     *    1 - [SELECTED_INDEX_ALL][SELECTED_INDEX_ALL]
     *    2 - [0][SELECTED_INDEX_ALL] ~ [maxDailyIndex][SELECTED_INDEX_ALL]
     *    3 - [0][0] ~ [maxDailyIndex][maxHourlyIndex]
     */
    @VisibleForTesting
    @Nullable
    static Map<Integer, Map<Integer, BatteryDiffData>> getBatteryUsageMap(
            final Context context,
            final List<BatteryLevelData.PeriodBatteryLevelData> hourlyBatteryLevelsPerDay,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
        if (batteryHistoryMap.isEmpty()) {
            return null;
        }
        final Map<Integer, Map<Integer, BatteryDiffData>> resultMap = new HashMap<>();
        // Insert diff data from [0][0] to [maxDailyIndex][maxHourlyIndex].
        insertHourlyUsageDiffData(
                context, hourlyBatteryLevelsPerDay, batteryHistoryMap, resultMap);
        // Insert diff data from [0][SELECTED_INDEX_ALL] to [maxDailyIndex][SELECTED_INDEX_ALL].
        insertDailyUsageDiffData(hourlyBatteryLevelsPerDay, resultMap);
        // Insert diff data [SELECTED_INDEX_ALL][SELECTED_INDEX_ALL].
        insertAllUsageDiffData(resultMap);
        // Compute the apps number before purge. Must put before purgeLowPercentageAndFakeData.
        final int countOfAppBeforePurge = getCountOfApps(resultMap);
        purgeLowPercentageAndFakeData(context, resultMap);
        // Compute the apps number after purge. Must put after purgeLowPercentageAndFakeData.
        final int countOfAppAfterPurge = getCountOfApps(resultMap);
        if (!isUsageMapValid(resultMap, hourlyBatteryLevelsPerDay)) {
            return null;
        }

        logAppCountMetrics(context, countOfAppBeforePurge, countOfAppAfterPurge);
        return resultMap;
    }

    @VisibleForTesting
    @Nullable
    static BatteryDiffData generateBatteryDiffData(
            final Context context,
            @Nullable final List<BatteryEntry> batteryEntryList,
            final BatteryUsageStats batteryUsageStats) {
        final List<BatteryHistEntry> batteryHistEntryList =
                convertToBatteryHistEntry(batteryEntryList, batteryUsageStats);
        if (batteryHistEntryList == null || batteryHistEntryList.isEmpty()) {
            Log.w(TAG, "batteryHistEntryList is null or empty in generateBatteryDiffData()");
            return null;
        }
        final int currentUserId = context.getUserId();
        final UserHandle userHandle =
                Utils.getManagedProfile(context.getSystemService(UserManager.class));
        final int workProfileUserId =
                userHandle != null ? userHandle.getIdentifier() : Integer.MIN_VALUE;
        final List<BatteryDiffEntry> appEntries = new ArrayList<>();
        final List<BatteryDiffEntry> systemEntries = new ArrayList<>();
        double totalConsumePower = 0f;
        double consumePowerFromOtherUsers = 0f;

        for (BatteryHistEntry entry : batteryHistEntryList) {
            final boolean isFromOtherUsers = isConsumedFromOtherUsers(
                    currentUserId, workProfileUserId, entry);
            totalConsumePower += entry.mConsumePower;
            if (isFromOtherUsers) {
                consumePowerFromOtherUsers += entry.mConsumePower;
            } else {
                final BatteryDiffEntry currentBatteryDiffEntry = new BatteryDiffEntry(
                        context,
                        entry.mForegroundUsageTimeInMs,
                        entry.mBackgroundUsageTimeInMs,
                        entry.mConsumePower,
                        entry);
                if (currentBatteryDiffEntry.isSystemEntry()) {
                    systemEntries.add(currentBatteryDiffEntry);
                } else {
                    appEntries.add(currentBatteryDiffEntry);
                }
            }
        }
        if (consumePowerFromOtherUsers != 0) {
            systemEntries.add(createOtherUsersEntry(context, consumePowerFromOtherUsers));
        }

        // If there is no data, return null instead of empty item.
        if (appEntries.isEmpty() && systemEntries.isEmpty()) {
            return null;
        }

        return new BatteryDiffData(appEntries, systemEntries, totalConsumePower);
    }

    /**
     * Starts the async task to load battery diff usage data and load app labels + icons.
     */
    private static void loadBatteryUsageDataFromBatteryStatsService(
            Context context,
            @Nullable Handler handler,
            final UsageMapAsyncResponse asyncResponseDelegate) {
        new LoadUsageMapFromBatteryStatsServiceTask(
                context,
                handler,
                asyncResponseDelegate).execute();
    }

    /**
     * @return Returns the overall battery usage data from battery stats service directly.
     *
     * The returned value should be always a 2d map and composed by only 1 part:
     * - [SELECTED_INDEX_ALL][SELECTED_INDEX_ALL]
     */
    @Nullable
    private static Map<Integer, Map<Integer, BatteryDiffData>> getBatteryUsageMapFromStatsService(
            final Context context) {
        final Map<Integer, Map<Integer, BatteryDiffData>> resultMap = new HashMap<>();
        final Map<Integer, BatteryDiffData> allUsageMap = new HashMap<>();
        // Always construct the map whether the value is null or not.
        allUsageMap.put(SELECTED_INDEX_ALL,
                getBatteryDiffDataFromBatteryStatsService(context));
        resultMap.put(SELECTED_INDEX_ALL, allUsageMap);

        // Compute the apps number before purge. Must put before purgeLowPercentageAndFakeData.
        final int countOfAppBeforePurge = getCountOfApps(resultMap);
        purgeLowPercentageAndFakeData(context, resultMap);
        // Compute the apps number after purge. Must put after purgeLowPercentageAndFakeData.
        final int countOfAppAfterPurge = getCountOfApps(resultMap);

        logAppCountMetrics(context, countOfAppBeforePurge, countOfAppAfterPurge);
        return resultMap;
    }

    @Nullable
    private static BatteryDiffData getBatteryDiffDataFromBatteryStatsService(
            final Context context) {
        BatteryDiffData batteryDiffData = null;
        try {
            final BatteryUsageStatsQuery batteryUsageStatsQuery =
                    new BatteryUsageStatsQuery.Builder().includeBatteryHistory().build();
            final BatteryUsageStats batteryUsageStats =
                    context.getSystemService(BatteryStatsManager.class)
                            .getBatteryUsageStats(batteryUsageStatsQuery);

            if (batteryUsageStats == null) {
                Log.w(TAG, "batteryUsageStats is null content");
                return null;
            }

            final List<BatteryEntry> batteryEntryList =
                    generateBatteryEntryListFromBatteryUsageStats(context, batteryUsageStats);
            batteryDiffData = generateBatteryDiffData(context, batteryEntryList, batteryUsageStats);
        } catch (RuntimeException e) {
            Log.e(TAG, "load batteryUsageStats:" + e);
        }

        return batteryDiffData;
    }

    @Nullable
    private static List<BatteryEntry> generateBatteryEntryListFromBatteryUsageStats(
            final Context context, final BatteryUsageStats batteryUsageStats) {
        // Loads the battery consuming data.
        final BatteryAppListPreferenceController controller =
                new BatteryAppListPreferenceController(
                        context,
                        /*preferenceKey=*/ null,
                        /*lifecycle=*/ null,
                        /*activity*=*/ null,
                        /*fragment=*/ null);
        return controller.getBatteryEntryList(batteryUsageStats, /*showAllApps=*/ true);
    }

    @Nullable
    private static List<BatteryHistEntry> convertToBatteryHistEntry(
            @Nullable final List<BatteryEntry> batteryEntryList,
            final BatteryUsageStats batteryUsageStats) {
        if (batteryEntryList == null || batteryEntryList.isEmpty()) {
            Log.w(TAG, "batteryEntryList is null or empty in convertToBatteryHistEntry()");
            return null;
        }
        return batteryEntryList.stream()
                .filter(entry -> {
                    final long foregroundMs = entry.getTimeInForegroundMs();
                    final long backgroundMs = entry.getTimeInBackgroundMs();
                    return entry.getConsumedPower() > 0
                            || (entry.getConsumedPower() == 0
                            && (foregroundMs != 0 || backgroundMs != 0));
                })
                .map(entry -> ConvertUtils.convertToBatteryHistEntry(
                        entry,
                        batteryUsageStats))
                .collect(Collectors.toList());
    }

    /**
     * Interpolates history map based on expected timestamp slots and processes the corner case when
     * the expected start timestamp is earlier than what we have.
     */
    private static void interpolateHistory(
            Context context,
            final List<Long> rawTimestampList,
            final List<Long> expectedTimestampSlots,
            final boolean isFromFullCharge,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap,
            final Map<Long, Map<String, BatteryHistEntry>> resultMap) {
        if (rawTimestampList.isEmpty() || expectedTimestampSlots.isEmpty()) {
            return;
        }
        final long expectedStartTimestamp = expectedTimestampSlots.get(0);
        final long rawStartTimestamp = rawTimestampList.get(0);
        int startIndex = 0;
        // If the expected start timestamp is full charge or earlier than what we have, use the
        // first data of what we have directly. This should be OK because the expected start
        // timestamp is the nearest even hour of the raw start timestamp, their time diff is no
        // more than 1 hour.
        if (isFromFullCharge || expectedStartTimestamp < rawStartTimestamp) {
            startIndex = 1;
            resultMap.put(expectedStartTimestamp, batteryHistoryMap.get(rawStartTimestamp));
        }
        final int expectedTimestampSlotsSize = expectedTimestampSlots.size();
        for (int index = startIndex; index < expectedTimestampSlotsSize; index++) {
            final long currentSlot = expectedTimestampSlots.get(index);
            final boolean isStartOrEnd = index == 0 || index == expectedTimestampSlotsSize - 1;
            interpolateHistoryForSlot(
                    context, currentSlot, rawTimestampList, batteryHistoryMap, resultMap,
                    isStartOrEnd);
        }
    }

    private static void interpolateHistoryForSlot(
            Context context,
            final long currentSlot,
            final List<Long> rawTimestampList,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap,
            final Map<Long, Map<String, BatteryHistEntry>> resultMap,
            final boolean isStartOrEnd) {
        final long[] nearestTimestamps = findNearestTimestamp(rawTimestampList, currentSlot);
        final long lowerTimestamp = nearestTimestamps[0];
        final long upperTimestamp = nearestTimestamps[1];
        // Case 1: upper timestamp is zero since scheduler is delayed!
        if (upperTimestamp == 0) {
            log(context, "job scheduler is delayed", currentSlot, null);
            resultMap.put(currentSlot, new HashMap<>());
            return;
        }
        // Case 2: upper timestamp is closed to the current timestamp.
        if ((upperTimestamp - currentSlot)
                < MAX_DIFF_SECONDS_OF_UPPER_TIMESTAMP * DateUtils.SECOND_IN_MILLIS) {
            log(context, "force align into the nearest slot", currentSlot, null);
            resultMap.put(currentSlot, batteryHistoryMap.get(upperTimestamp));
            return;
        }
        // Case 3: lower timestamp is zero before starting to collect data.
        if (lowerTimestamp == 0) {
            log(context, "no lower timestamp slot data", currentSlot, null);
            resultMap.put(currentSlot, new HashMap<>());
            return;
        }
        interpolateHistoryForSlot(context,
                currentSlot, lowerTimestamp, upperTimestamp, batteryHistoryMap, resultMap,
                isStartOrEnd);
    }

    private static void interpolateHistoryForSlot(
            Context context,
            final long currentSlot,
            final long lowerTimestamp,
            final long upperTimestamp,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap,
            final Map<Long, Map<String, BatteryHistEntry>> resultMap,
            final boolean isStartOrEnd) {
        final Map<String, BatteryHistEntry> lowerEntryDataMap =
                batteryHistoryMap.get(lowerTimestamp);
        final Map<String, BatteryHistEntry> upperEntryDataMap =
                batteryHistoryMap.get(upperTimestamp);
        // Verifies whether the lower data is valid to use or not by checking boot time.
        final BatteryHistEntry upperEntryDataFirstEntry =
                upperEntryDataMap.values().stream().findFirst().get();
        final long upperEntryDataBootTimestamp =
                upperEntryDataFirstEntry.mTimestamp - upperEntryDataFirstEntry.mBootTimestamp;
        // Lower data is captured before upper data corresponding device is booting.
        // Skips the booting-specific logics and always does interpolation for daily chart level
        // data.
        if (lowerTimestamp < upperEntryDataBootTimestamp
                && !isForDailyChart(isStartOrEnd, currentSlot)) {
            // Provides an opportunity to force align the slot directly.
            if ((upperTimestamp - currentSlot) < 10 * DateUtils.MINUTE_IN_MILLIS) {
                log(context, "force align into the nearest slot", currentSlot, null);
                resultMap.put(currentSlot, upperEntryDataMap);
            } else {
                log(context, "in the different booting section", currentSlot, null);
                resultMap.put(currentSlot, new HashMap<>());
            }
            return;
        }
        log(context, "apply interpolation arithmetic", currentSlot, null);
        final Map<String, BatteryHistEntry> newHistEntryMap = new HashMap<>();
        final double timestampLength = upperTimestamp - lowerTimestamp;
        final double timestampDiff = currentSlot - lowerTimestamp;
        // Applies interpolation arithmetic for each BatteryHistEntry.
        for (String entryKey : upperEntryDataMap.keySet()) {
            final BatteryHistEntry lowerEntry = lowerEntryDataMap.get(entryKey);
            final BatteryHistEntry upperEntry = upperEntryDataMap.get(entryKey);
            // Checks whether there is any abnormal battery reset conditions.
            if (lowerEntry != null) {
                final boolean invalidForegroundUsageTime =
                        lowerEntry.mForegroundUsageTimeInMs > upperEntry.mForegroundUsageTimeInMs;
                final boolean invalidBackgroundUsageTime =
                        lowerEntry.mBackgroundUsageTimeInMs > upperEntry.mBackgroundUsageTimeInMs;
                if (invalidForegroundUsageTime || invalidBackgroundUsageTime) {
                    newHistEntryMap.put(entryKey, upperEntry);
                    log(context, "abnormal reset condition is found", currentSlot, upperEntry);
                    continue;
                }
            }
            final BatteryHistEntry newEntry =
                    BatteryHistEntry.interpolate(
                            currentSlot,
                            upperTimestamp,
                            /*ratio=*/ timestampDiff / timestampLength,
                            lowerEntry,
                            upperEntry);
            newHistEntryMap.put(entryKey, newEntry);
            if (lowerEntry == null) {
                log(context, "cannot find lower entry data", currentSlot, upperEntry);
                continue;
            }
        }
        resultMap.put(currentSlot, newHistEntryMap);
    }

    /**
     * @return Returns the nearest even hour timestamp of the given timestamp.
     */
    private static long getNearestEvenHourTimestamp(long rawTimestamp) {
        // If raw hour is even, the nearest even hour should be the even hour before raw
        // start. The hour doesn't need to change and just set the minutes and seconds to 0.
        // Otherwise, the nearest even hour should be raw hour + 1.
        // For example, the nearest hour of 14:30:50 should be 14:00:00. While the nearest
        // hour of 15:30:50 should be 16:00:00.
        return getEvenHourTimestamp(rawTimestamp, /*addHourOfDay*/ 1);
    }

    /**
     * @return Returns the last even hour timestamp before the given timestamp.
     */
    private static long getLastEvenHourBeforeTimestamp(long rawTimestamp) {
        // If raw hour is even, the hour doesn't need to change as well.
        // Otherwise, the even hour before raw end should be raw hour - 1.
        // For example, the even hour before 14:30:50 should be 14:00:00. While the even
        // hour before 15:30:50 should be 14:00:00.
        return getEvenHourTimestamp(rawTimestamp, /*addHourOfDay*/ -1);
    }

    private static long getEvenHourTimestamp(long rawTimestamp, int addHourOfDay) {
        final Calendar evenHourCalendar = Calendar.getInstance();
        evenHourCalendar.setTimeInMillis(rawTimestamp);
        // Before computing the evenHourCalendar, record raw hour based on local timezone.
        final int rawHour = evenHourCalendar.get(Calendar.HOUR_OF_DAY);
        if (rawHour % 2 != 0) {
            evenHourCalendar.add(Calendar.HOUR_OF_DAY, addHourOfDay);
        }
        evenHourCalendar.set(Calendar.MINUTE, 0);
        evenHourCalendar.set(Calendar.SECOND, 0);
        evenHourCalendar.set(Calendar.MILLISECOND, 0);
        return evenHourCalendar.getTimeInMillis();
    }

    private static List<List<Long>> getHourlyTimestamps(final List<Long> dailyTimestamps) {
        final List<List<Long>> hourlyTimestamps = new ArrayList<>();
        if (dailyTimestamps.size() < MIN_DAILY_DATA_SIZE) {
            return hourlyTimestamps;
        }

        for (int dailyStartIndex = 0; dailyStartIndex < dailyTimestamps.size() - 1;
                dailyStartIndex++) {
            long currentTimestamp = dailyTimestamps.get(dailyStartIndex);
            final long dailyEndTimestamp = dailyTimestamps.get(dailyStartIndex + 1);
            final List<Long> hourlyTimestampsPerDay = new ArrayList<>();
            while (currentTimestamp <= dailyEndTimestamp) {
                hourlyTimestampsPerDay.add(currentTimestamp);
                currentTimestamp += MIN_TIME_SLOT;
            }
            hourlyTimestamps.add(hourlyTimestampsPerDay);
        }
        return hourlyTimestamps;
    }

    private static List<BatteryLevelData.PeriodBatteryLevelData> getHourlyPeriodBatteryLevelData(
            Context context,
            final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap,
            final List<List<Long>> timestamps) {
        final List<BatteryLevelData.PeriodBatteryLevelData> levelData = new ArrayList<>();
        timestamps.forEach(
                timestampList -> levelData.add(
                        getPeriodBatteryLevelData(
                                context, processedBatteryHistoryMap, timestampList)));
        return levelData;
    }

    private static BatteryLevelData.PeriodBatteryLevelData getPeriodBatteryLevelData(
            Context context,
            final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap,
            final List<Long> timestamps) {
        final List<Integer> levels = new ArrayList<>();
        timestamps.forEach(
                timestamp -> levels.add(getLevel(context, processedBatteryHistoryMap, timestamp)));
        return new BatteryLevelData.PeriodBatteryLevelData(timestamps, levels);
    }

    private static Integer getLevel(
            Context context,
            final Map<Long, Map<String, BatteryHistEntry>> processedBatteryHistoryMap,
            final long timestamp) {
        final Map<String, BatteryHistEntry> entryMap = processedBatteryHistoryMap.get(timestamp);
        if (entryMap == null || entryMap.isEmpty()) {
            Log.e(TAG, "abnormal entry list in the timestamp:"
                    + utcToLocalTime(context, timestamp));
            return null;
        }
        // Averages the battery level in each time slot to avoid corner conditions.
        float batteryLevelCounter = 0;
        for (BatteryHistEntry entry : entryMap.values()) {
            batteryLevelCounter += entry.mBatteryLevel;
        }
        return Math.round(batteryLevelCounter / entryMap.size());
    }

    private static void insertHourlyUsageDiffData(
            Context context,
            final List<BatteryLevelData.PeriodBatteryLevelData> hourlyBatteryLevelsPerDay,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap,
            final Map<Integer, Map<Integer, BatteryDiffData>> resultMap) {
        final int currentUserId = context.getUserId();
        final UserHandle userHandle =
                Utils.getManagedProfile(context.getSystemService(UserManager.class));
        final int workProfileUserId =
                userHandle != null ? userHandle.getIdentifier() : Integer.MIN_VALUE;
        // Each time slot usage diff data =
        //     Math.abs(timestamp[i+2] data - timestamp[i+1] data) +
        //     Math.abs(timestamp[i+1] data - timestamp[i] data);
        // since we want to aggregate every two hours data into a single time slot.
        for (int dailyIndex = 0; dailyIndex < hourlyBatteryLevelsPerDay.size(); dailyIndex++) {
            final Map<Integer, BatteryDiffData> dailyDiffMap = new HashMap<>();
            resultMap.put(dailyIndex, dailyDiffMap);
            if (hourlyBatteryLevelsPerDay.get(dailyIndex) == null) {
                continue;
            }
            final List<Long> timestamps = hourlyBatteryLevelsPerDay.get(dailyIndex).getTimestamps();
            for (int hourlyIndex = 0; hourlyIndex < timestamps.size() - 1; hourlyIndex++) {
                final BatteryDiffData hourlyBatteryDiffData =
                        insertHourlyUsageDiffDataPerSlot(
                                context,
                                currentUserId,
                                workProfileUserId,
                                hourlyIndex,
                                timestamps,
                                batteryHistoryMap);
                dailyDiffMap.put(hourlyIndex, hourlyBatteryDiffData);
            }
        }
    }

    private static void insertDailyUsageDiffData(
            final List<BatteryLevelData.PeriodBatteryLevelData> hourlyBatteryLevelsPerDay,
            final Map<Integer, Map<Integer, BatteryDiffData>> resultMap) {
        for (int index = 0; index < hourlyBatteryLevelsPerDay.size(); index++) {
            Map<Integer, BatteryDiffData> dailyUsageMap = resultMap.get(index);
            if (dailyUsageMap == null) {
                dailyUsageMap = new HashMap<>();
                resultMap.put(index, dailyUsageMap);
            }
            dailyUsageMap.put(
                    SELECTED_INDEX_ALL,
                    getAccumulatedUsageDiffData(dailyUsageMap.values()));
        }
    }

    private static void insertAllUsageDiffData(
            final Map<Integer, Map<Integer, BatteryDiffData>> resultMap) {
        final List<BatteryDiffData> diffDataList = new ArrayList<>();
        resultMap.keySet().forEach(
                key -> diffDataList.add(resultMap.get(key).get(SELECTED_INDEX_ALL)));
        final Map<Integer, BatteryDiffData> allUsageMap = new HashMap<>();
        allUsageMap.put(SELECTED_INDEX_ALL, getAccumulatedUsageDiffData(diffDataList));
        resultMap.put(SELECTED_INDEX_ALL, allUsageMap);
    }

    @Nullable
    private static BatteryDiffData insertHourlyUsageDiffDataPerSlot(
            Context context,
            final int currentUserId,
            final int workProfileUserId,
            final int currentIndex,
            final List<Long> timestamps,
            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
        final List<BatteryDiffEntry> appEntries = new ArrayList<>();
        final List<BatteryDiffEntry> systemEntries = new ArrayList<>();

        final Long currentTimestamp = timestamps.get(currentIndex);
        final Long nextTimestamp = currentTimestamp + DateUtils.HOUR_IN_MILLIS;
        final Long nextTwoTimestamp = nextTimestamp + DateUtils.HOUR_IN_MILLIS;
        // Fetches BatteryHistEntry data from corresponding time slot.
        final Map<String, BatteryHistEntry> currentBatteryHistMap =
                batteryHistoryMap.getOrDefault(currentTimestamp, EMPTY_BATTERY_MAP);
        final Map<String, BatteryHistEntry> nextBatteryHistMap =
                batteryHistoryMap.getOrDefault(nextTimestamp, EMPTY_BATTERY_MAP);
        final Map<String, BatteryHistEntry> nextTwoBatteryHistMap =
                batteryHistoryMap.getOrDefault(nextTwoTimestamp, EMPTY_BATTERY_MAP);
        // We should not get the empty list since we have at least one fake data to record
        // the battery level and status in each time slot, the empty list is used to
        // represent there is no enough data to apply interpolation arithmetic.
        if (currentBatteryHistMap.isEmpty()
                || nextBatteryHistMap.isEmpty()
                || nextTwoBatteryHistMap.isEmpty()) {
            return null;
        }

        // Collects all keys in these three time slot records as all populations.
        final Set<String> allBatteryHistEntryKeys = new ArraySet<>();
        allBatteryHistEntryKeys.addAll(currentBatteryHistMap.keySet());
        allBatteryHistEntryKeys.addAll(nextBatteryHistMap.keySet());
        allBatteryHistEntryKeys.addAll(nextTwoBatteryHistMap.keySet());

        double totalConsumePower = 0.0;
        double consumePowerFromOtherUsers = 0f;
        // Calculates all packages diff usage data in a specific time slot.
        for (String key : allBatteryHistEntryKeys) {
            final BatteryHistEntry currentEntry =
                    currentBatteryHistMap.getOrDefault(key, EMPTY_BATTERY_HIST_ENTRY);
            final BatteryHistEntry nextEntry =
                    nextBatteryHistMap.getOrDefault(key, EMPTY_BATTERY_HIST_ENTRY);
            final BatteryHistEntry nextTwoEntry =
                    nextTwoBatteryHistMap.getOrDefault(key, EMPTY_BATTERY_HIST_ENTRY);
            // Cumulative values is a specific time slot for a specific app.
            long foregroundUsageTimeInMs =
                    getDiffValue(
                            currentEntry.mForegroundUsageTimeInMs,
                            nextEntry.mForegroundUsageTimeInMs,
                            nextTwoEntry.mForegroundUsageTimeInMs);
            long backgroundUsageTimeInMs =
                    getDiffValue(
                            currentEntry.mBackgroundUsageTimeInMs,
                            nextEntry.mBackgroundUsageTimeInMs,
                            nextTwoEntry.mBackgroundUsageTimeInMs);
            double consumePower =
                    getDiffValue(
                            currentEntry.mConsumePower,
                            nextEntry.mConsumePower,
                            nextTwoEntry.mConsumePower);
            // Excludes entry since we don't have enough data to calculate.
            if (foregroundUsageTimeInMs == 0
                    && backgroundUsageTimeInMs == 0
                    && consumePower == 0) {
                continue;
            }
            final BatteryHistEntry selectedBatteryEntry =
                    selectBatteryHistEntry(currentEntry, nextEntry, nextTwoEntry);
            if (selectedBatteryEntry == null) {
                continue;
            }
            // Forces refine the cumulative value since it may introduce deviation error since we
            // will apply the interpolation arithmetic.
            final float totalUsageTimeInMs =
                    foregroundUsageTimeInMs + backgroundUsageTimeInMs;
            if (totalUsageTimeInMs > TOTAL_HOURLY_TIME_THRESHOLD) {
                final float ratio = TOTAL_HOURLY_TIME_THRESHOLD / totalUsageTimeInMs;
                if (DEBUG) {
                    Log.w(TAG, String.format("abnormal usage time %d|%d for:\n%s",
                            Duration.ofMillis(foregroundUsageTimeInMs).getSeconds(),
                            Duration.ofMillis(backgroundUsageTimeInMs).getSeconds(),
                            currentEntry));
                }
                foregroundUsageTimeInMs =
                        Math.round(foregroundUsageTimeInMs * ratio);
                backgroundUsageTimeInMs =
                        Math.round(backgroundUsageTimeInMs * ratio);
                consumePower = consumePower * ratio;
            }
            totalConsumePower += consumePower;

            final boolean isFromOtherUsers = isConsumedFromOtherUsers(
                    currentUserId, workProfileUserId, selectedBatteryEntry);
            if (isFromOtherUsers) {
                consumePowerFromOtherUsers += consumePower;
            } else {
                final BatteryDiffEntry currentBatteryDiffEntry = new BatteryDiffEntry(
                        context,
                        foregroundUsageTimeInMs,
                        backgroundUsageTimeInMs,
                        consumePower,
                        selectedBatteryEntry);
                if (currentBatteryDiffEntry.isSystemEntry()) {
                    systemEntries.add(currentBatteryDiffEntry);
                } else {
                    appEntries.add(currentBatteryDiffEntry);
                }
            }
        }
        if (consumePowerFromOtherUsers != 0) {
            systemEntries.add(createOtherUsersEntry(context, consumePowerFromOtherUsers));
        }

        // If there is no data, return null instead of empty item.
        if (appEntries.isEmpty() && systemEntries.isEmpty()) {
            return null;
        }

        final BatteryDiffData resultDiffData =
                new BatteryDiffData(appEntries, systemEntries, totalConsumePower);
        return resultDiffData;
    }

    private static boolean isConsumedFromOtherUsers(
            final int currentUserId,
            final int workProfileUserId,
            final BatteryHistEntry batteryHistEntry) {
        return batteryHistEntry.mConsumerType == ConvertUtils.CONSUMER_TYPE_UID_BATTERY
                && batteryHistEntry.mUserId != currentUserId
                && batteryHistEntry.mUserId != workProfileUserId;
    }

    @Nullable
    private static BatteryDiffData getAccumulatedUsageDiffData(
            final Collection<BatteryDiffData> diffEntryListData) {
        double totalConsumePower = 0f;
        final Map<String, BatteryDiffEntry> diffEntryMap = new HashMap<>();
        final List<BatteryDiffEntry> appEntries = new ArrayList<>();
        final List<BatteryDiffEntry> systemEntries = new ArrayList<>();

        for (BatteryDiffData diffEntryList : diffEntryListData) {
            if (diffEntryList == null) {
                continue;
            }
            for (BatteryDiffEntry entry : diffEntryList.getAppDiffEntryList()) {
                computeUsageDiffDataPerEntry(entry, diffEntryMap);
                totalConsumePower += entry.mConsumePower;
            }
            for (BatteryDiffEntry entry : diffEntryList.getSystemDiffEntryList()) {
                computeUsageDiffDataPerEntry(entry, diffEntryMap);
                totalConsumePower += entry.mConsumePower;
            }
        }

        final Collection<BatteryDiffEntry> diffEntryList = diffEntryMap.values();
        for (BatteryDiffEntry entry : diffEntryList) {
            // Sets total daily consume power data into all BatteryDiffEntry.
            entry.setTotalConsumePower(totalConsumePower);
            if (entry.isSystemEntry()) {
                systemEntries.add(entry);
            } else {
                appEntries.add(entry);
            }
        }

        return diffEntryList.isEmpty() ? null : new BatteryDiffData(appEntries, systemEntries);
    }

    private static void computeUsageDiffDataPerEntry(
            final BatteryDiffEntry entry,
            final Map<String, BatteryDiffEntry> diffEntryMap) {
        final String key = entry.mBatteryHistEntry.getKey();
        final BatteryDiffEntry oldBatteryDiffEntry = diffEntryMap.get(key);
        // Creates new BatteryDiffEntry if we don't have it.
        if (oldBatteryDiffEntry == null) {
            diffEntryMap.put(key, entry.clone());
        } else {
            // Sums up some field data into the existing one.
            oldBatteryDiffEntry.mForegroundUsageTimeInMs +=
                    entry.mForegroundUsageTimeInMs;
            oldBatteryDiffEntry.mBackgroundUsageTimeInMs +=
                    entry.mBackgroundUsageTimeInMs;
            oldBatteryDiffEntry.mConsumePower += entry.mConsumePower;
        }
    }

    // Removes low percentage data and fake usage data, which will be zero value.
    private static void purgeLowPercentageAndFakeData(
            final Context context,
            final Map<Integer, Map<Integer, BatteryDiffData>> resultMap) {
        final Set<CharSequence> backgroundUsageTimeHideList =
                FeatureFactory.getFactory(context)
                        .getPowerUsageFeatureProvider(context)
                        .getHideBackgroundUsageTimeSet(context);
        final CharSequence[] notAllowShowEntryPackages =
                FeatureFactory.getFactory(context)
                        .getPowerUsageFeatureProvider(context)
                        .getHideApplicationEntries(context);
        resultMap.keySet().forEach(dailyKey -> {
            final Map<Integer, BatteryDiffData> dailyUsageMap = resultMap.get(dailyKey);
            dailyUsageMap.values().forEach(diffEntryLists -> {
                if (diffEntryLists == null) {
                    return;
                }
                purgeLowPercentageAndFakeData(
                        diffEntryLists.getAppDiffEntryList(), backgroundUsageTimeHideList,
                        notAllowShowEntryPackages);
                purgeLowPercentageAndFakeData(
                        diffEntryLists.getSystemDiffEntryList(), backgroundUsageTimeHideList,
                        notAllowShowEntryPackages);
            });
        });
    }

    private static void purgeLowPercentageAndFakeData(
            final List<BatteryDiffEntry> entries,
            final Set<CharSequence> backgroundUsageTimeHideList,
            final CharSequence[] notAllowShowEntryPackages) {
        final Iterator<BatteryDiffEntry> iterator = entries.iterator();
        while (iterator.hasNext()) {
            final BatteryDiffEntry entry = iterator.next();
            final String packageName = entry.getPackageName();
            if (entry.getPercentOfTotal() < PERCENTAGE_OF_TOTAL_THRESHOLD
                    || FAKE_PACKAGE_NAME.equals(packageName)
                    || contains(packageName, notAllowShowEntryPackages)) {
                iterator.remove();
            }
            if (packageName != null
                    && !backgroundUsageTimeHideList.isEmpty()
                    && contains(packageName, backgroundUsageTimeHideList)) {
                entry.mBackgroundUsageTimeInMs = 0;
            }
        }
    }

    private static boolean isUsageMapValid(
            final Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap,
            final List<BatteryLevelData.PeriodBatteryLevelData> hourlyBatteryLevelsPerDay) {
        if (batteryUsageMap.get(SELECTED_INDEX_ALL) == null
                || !batteryUsageMap.get(SELECTED_INDEX_ALL).containsKey(SELECTED_INDEX_ALL)) {
            Log.e(TAG, "no [SELECTED_INDEX_ALL][SELECTED_INDEX_ALL] in batteryUsageMap");
            return false;
        }
        for (int dailyIndex = 0; dailyIndex < hourlyBatteryLevelsPerDay.size(); dailyIndex++) {
            if (batteryUsageMap.get(dailyIndex) == null
                    || !batteryUsageMap.get(dailyIndex).containsKey(SELECTED_INDEX_ALL)) {
                Log.e(TAG, "no [" + dailyIndex + "][SELECTED_INDEX_ALL] in batteryUsageMap, "
                        + "daily size is: " + hourlyBatteryLevelsPerDay.size());
                return false;
            }
            if (hourlyBatteryLevelsPerDay.get(dailyIndex) == null) {
                continue;
            }
            final List<Long> timestamps = hourlyBatteryLevelsPerDay.get(dailyIndex).getTimestamps();
            // Length of hourly usage map should be the length of hourly level data - 1.
            for (int hourlyIndex = 0; hourlyIndex < timestamps.size() - 1; hourlyIndex++) {
                if (!batteryUsageMap.get(dailyIndex).containsKey(hourlyIndex)) {
                    Log.e(TAG, "no [" + dailyIndex + "][" + hourlyIndex + "] in batteryUsageMap, "
                            + "hourly size is: " + (timestamps.size() - 1));
                    return false;
                }
            }
        }
        return true;
    }

    private static void loadLabelAndIcon(
            @Nullable final Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap) {
        if (batteryUsageMap == null) {
            return;
        }
        // Pre-loads each BatteryDiffEntry relative icon and label for all slots.
        final BatteryDiffData batteryUsageMapForAll =
                batteryUsageMap.get(SELECTED_INDEX_ALL).get(SELECTED_INDEX_ALL);
        if (batteryUsageMapForAll != null) {
            batteryUsageMapForAll.getAppDiffEntryList().forEach(
                    entry -> entry.loadLabelAndIcon());
            batteryUsageMapForAll.getSystemDiffEntryList().forEach(
                    entry -> entry.loadLabelAndIcon());
        }
    }

    private static long getTimestampWithDayDiff(final long timestamp, final int dayDiff) {
        final Calendar calendar = Calendar.getInstance();
        calendar.setTimeInMillis(timestamp);
        calendar.add(Calendar.DAY_OF_YEAR, dayDiff);
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        return calendar.getTimeInMillis();
    }

    private static int getCountOfApps(final Map<Integer, Map<Integer, BatteryDiffData>> resultMap) {
        final BatteryDiffData diffDataList =
                resultMap.get(SELECTED_INDEX_ALL).get(SELECTED_INDEX_ALL);
        return diffDataList == null
                ? 0
                : diffDataList.getAppDiffEntryList().size()
                        + diffDataList.getSystemDiffEntryList().size();
    }

    private static boolean contains(String target, Set<CharSequence> packageNames) {
        if (target != null && packageNames != null) {
            for (CharSequence packageName : packageNames) {
                if (TextUtils.equals(target, packageName)) {
                    return true;
                }
            }
        }
        return false;
    }

    private static long getDiffValue(long v1, long v2, long v3) {
        return (v2 > v1 ? v2 - v1 : 0) + (v3 > v2 ? v3 - v2 : 0);
    }

    private static double getDiffValue(double v1, double v2, double v3) {
        return (v2 > v1 ? v2 - v1 : 0) + (v3 > v2 ? v3 - v2 : 0);
    }

    @Nullable
    private static BatteryHistEntry selectBatteryHistEntry(
            final BatteryHistEntry... batteryHistEntries) {
        for (BatteryHistEntry entry : batteryHistEntries) {
            if (entry != null && entry != EMPTY_BATTERY_HIST_ENTRY) {
                return entry;
            }
        }
        return null;
    }

    private static BatteryDiffEntry createOtherUsersEntry(
            Context context, final double consumePower) {
        final ContentValues values = new ContentValues();
        values.put(BatteryHistEntry.KEY_UID, BatteryUtils.UID_OTHER_USERS);
        values.put(BatteryHistEntry.KEY_USER_ID, BatteryUtils.UID_OTHER_USERS);
        values.put(BatteryHistEntry.KEY_CONSUMER_TYPE, ConvertUtils.CONSUMER_TYPE_UID_BATTERY);
        // We will show the percentage for the "other users" item only, the aggregated
        // running time information is useless for users to identify individual apps.
        final BatteryDiffEntry batteryDiffEntry = new BatteryDiffEntry(
                context,
                /*foregroundUsageTimeInMs=*/ 0,
                /*backgroundUsageTimeInMs=*/ 0,
                consumePower,
                new BatteryHistEntry(values));
        return batteryDiffEntry;
    }

    private static void logAppCountMetrics(
            Context context, final int countOfAppBeforePurge, final int countOfAppAfterPurge) {
        context = context.getApplicationContext();
        final MetricsFeatureProvider metricsFeatureProvider =
                FeatureFactory.getFactory(context).getMetricsFeatureProvider();
        metricsFeatureProvider.action(
                context,
                SettingsEnums.ACTION_BATTERY_USAGE_SHOWN_APP_COUNT,
                countOfAppAfterPurge);
        metricsFeatureProvider.action(
                context,
                SettingsEnums.ACTION_BATTERY_USAGE_HIDDEN_APP_COUNT,
                countOfAppBeforePurge - countOfAppAfterPurge);
    }

    private static void log(Context context, final String content, final long timestamp,
            final BatteryHistEntry entry) {
        if (DEBUG) {
            Log.d(TAG, String.format(entry != null ? "%s %s:\n%s" : "%s %s:%s",
                    utcToLocalTime(context, timestamp), content, entry));
        }
    }

    // Compute diff map and loads all items (icon and label) in the background.
    private static class ComputeUsageMapAndLoadItemsTask
            extends AsyncTask<Void, Void, Map<Integer, Map<Integer, BatteryDiffData>>> {

        Context mApplicationContext;
        final Handler mHandler;
        final UsageMapAsyncResponse mAsyncResponseDelegate;
        private List<BatteryLevelData.PeriodBatteryLevelData> mHourlyBatteryLevelsPerDay;
        private Map<Long, Map<String, BatteryHistEntry>> mBatteryHistoryMap;

        private ComputeUsageMapAndLoadItemsTask(
                Context context,
                Handler handler,
                final UsageMapAsyncResponse asyncResponseDelegate,
                final List<BatteryLevelData.PeriodBatteryLevelData> hourlyBatteryLevelsPerDay,
                final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
            mApplicationContext = context.getApplicationContext();
            mHandler = handler;
            mAsyncResponseDelegate = asyncResponseDelegate;
            mHourlyBatteryLevelsPerDay = hourlyBatteryLevelsPerDay;
            mBatteryHistoryMap = batteryHistoryMap;
        }

        @Override
        protected Map<Integer, Map<Integer, BatteryDiffData>> doInBackground(Void... voids) {
            if (mApplicationContext == null
                    || mHandler == null
                    || mAsyncResponseDelegate == null
                    || mBatteryHistoryMap == null
                    || mHourlyBatteryLevelsPerDay == null) {
                Log.e(TAG, "invalid input for ComputeUsageMapAndLoadItemsTask()");
                return null;
            }
            final long startTime = System.currentTimeMillis();
            final Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap =
                    getBatteryUsageMap(
                            mApplicationContext, mHourlyBatteryLevelsPerDay, mBatteryHistoryMap);
            loadLabelAndIcon(batteryUsageMap);
            Log.d(TAG, String.format("execute ComputeUsageMapAndLoadItemsTask in %d/ms",
                    (System.currentTimeMillis() - startTime)));
            return batteryUsageMap;
        }

        @Override
        protected void onPostExecute(
                final Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap) {
            mApplicationContext = null;
            mHourlyBatteryLevelsPerDay = null;
            mBatteryHistoryMap = null;
            // Post results back to main thread to refresh UI.
            if (mHandler != null && mAsyncResponseDelegate != null) {
                mHandler.post(() -> {
                    mAsyncResponseDelegate.onBatteryUsageMapLoaded(batteryUsageMap);
                });
            }
        }
    }

    // Loads battery usage data from battery stats service directly and loads all items (icon and
    // label) in the background.
    private static final class LoadUsageMapFromBatteryStatsServiceTask
            extends ComputeUsageMapAndLoadItemsTask {

        private LoadUsageMapFromBatteryStatsServiceTask(
                Context context,
                Handler handler,
                final UsageMapAsyncResponse asyncResponseDelegate) {
            super(context, handler, asyncResponseDelegate, /*hourlyBatteryLevelsPerDay=*/ null,
                    /*batteryHistoryMap=*/ null);
        }

        @Override
        protected Map<Integer, Map<Integer, BatteryDiffData>> doInBackground(Void... voids) {
            if (mApplicationContext == null
                    || mHandler == null
                    || mAsyncResponseDelegate == null) {
                Log.e(TAG, "invalid input for ComputeUsageMapAndLoadItemsTask()");
                return null;
            }
            final long startTime = System.currentTimeMillis();
            final Map<Integer, Map<Integer, BatteryDiffData>> batteryUsageMap =
                    getBatteryUsageMapFromStatsService(mApplicationContext);
            loadLabelAndIcon(batteryUsageMap);
            Log.d(TAG, String.format("execute LoadUsageMapFromBatteryStatsServiceTask in %d/ms",
                    (System.currentTimeMillis() - startTime)));
            return batteryUsageMap;
        }
    }
}