Battery usage page latency improvement (1-8)

Save battery slot diff data into database in hourly job. Then read the
saved diff data and only calculate the remaining data. This could speed
up the battery usage loading.

Bug: 261163071
Fix: 261163071
Test: manual
Change-Id: Icd4868ca9326b64b17ddbccdb0311e755dc68026

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

@@ -16,15 +16,28 @@
 
 package com.android.settings.fuelgauge.batteryusage;
 
+import static com.android.settingslib.fuelgauge.BatteryStatus.BATTERY_LEVEL_UNKNOWN;
+
+import android.text.format.DateUtils;
+import android.util.ArrayMap;
+
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
 import androidx.core.util.Preconditions;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Objects;
 
 /** Wraps the battery timestamp and level data used for battery usage chart. */
 public final class BatteryLevelData {
+    private static final long MIN_SIZE = 2;
+    private static final long TIME_SLOT = DateUtils.HOUR_IN_MILLIS * 2;
+
     /** A container for the battery timestamp and level data. */
     public static final class PeriodBatteryLevelData {
         // The length of mTimestamps and mLevels must be the same. mLevels[index] might be null when
@@ -33,12 +46,14 @@ public final class BatteryLevelData {
         private final List<Integer> mLevels;
 
         public PeriodBatteryLevelData(
-                @NonNull List<Long> timestamps, @NonNull List<Integer> levels) {
-            Preconditions.checkArgument(timestamps.size() == levels.size(),
-                    /* errorMessage= */ "Timestamp: " + timestamps.size() + ", Level: "
-                            + levels.size());
+                @NonNull Map<Long, Integer> batteryLevelMap,
+                @NonNull List<Long> timestamps) {
             mTimestamps = timestamps;
-            mLevels = levels;
+            mLevels = new ArrayList<>(timestamps.size());
+            for (Long timestamp : timestamps) {
+                mLevels.add(batteryLevelMap.containsKey(timestamp)
+                        ? batteryLevelMap.get(timestamp) : BATTERY_LEVEL_UNKNOWN);
+            }
         }
 
         public List<Long> getTimestamps() {
@@ -68,15 +83,21 @@ public final class BatteryLevelData {
     // The size of hourly data must be the size of daily data - 1.
     private final List<PeriodBatteryLevelData> mHourlyBatteryLevelsPerDay;
 
-    public BatteryLevelData(
-            @NonNull PeriodBatteryLevelData dailyBatteryLevels,
-            @NonNull List<PeriodBatteryLevelData> hourlyBatteryLevelsPerDay) {
-        final long dailySize = dailyBatteryLevels.getTimestamps().size();
-        final long hourlySize = hourlyBatteryLevelsPerDay.size();
-        Preconditions.checkArgument(hourlySize == dailySize - 1,
-                /* errorMessage= */ "DailySize: " + dailySize + ", HourlySize: " + hourlySize);
-        mDailyBatteryLevels = dailyBatteryLevels;
-        mHourlyBatteryLevelsPerDay = hourlyBatteryLevelsPerDay;
+    public BatteryLevelData(@NonNull Map<Long, Integer> batteryLevelMap) {
+        final int mapSize = batteryLevelMap.size();
+        Preconditions.checkArgument(mapSize >= MIN_SIZE, "batteryLevelMap size:" + mapSize);
+
+        final List<Long> timestampList = new ArrayList<>(batteryLevelMap.keySet());
+        Collections.sort(timestampList);
+        final List<Long> dailyTimestamps = getDailyTimestamps(timestampList);
+        final List<List<Long>> hourlyTimestamps = getHourlyTimestamps(dailyTimestamps);
+
+        mDailyBatteryLevels = new PeriodBatteryLevelData(batteryLevelMap, dailyTimestamps);
+        mHourlyBatteryLevelsPerDay = new ArrayList<>(hourlyTimestamps.size());
+        for (List<Long> hourlyTimestampsPerDay : hourlyTimestamps) {
+            mHourlyBatteryLevelsPerDay.add(
+                    new PeriodBatteryLevelData(batteryLevelMap, hourlyTimestampsPerDay));
+        }
     }
 
     public PeriodBatteryLevelData getDailyBatteryLevels() {
@@ -94,5 +115,69 @@ public final class BatteryLevelData {
                 Objects.toString(mDailyBatteryLevels),
                 Objects.toString(mHourlyBatteryLevelsPerDay));
     }
+
+    @Nullable
+    static BatteryLevelData combine(@Nullable BatteryLevelData existingBatteryLevelData,
+            List<BatteryEvent> batteryLevelRecordEvents) {
+        final Map<Long, Integer> batteryLevelMap = new ArrayMap<>(batteryLevelRecordEvents.size());
+        for (BatteryEvent event : batteryLevelRecordEvents) {
+            batteryLevelMap.put(event.getTimestamp(), event.getBatteryLevel());
+        }
+        if (existingBatteryLevelData != null) {
+            List<PeriodBatteryLevelData> multiDaysData =
+                    existingBatteryLevelData.getHourlyBatteryLevelsPerDay();
+            for (int dayIndex = 0; dayIndex < multiDaysData.size(); dayIndex++) {
+                PeriodBatteryLevelData oneDayData = multiDaysData.get(dayIndex);
+                for (int hourIndex = 0; hourIndex < oneDayData.getLevels().size(); hourIndex++) {
+                    batteryLevelMap.put(oneDayData.getTimestamps().get(hourIndex),
+                            oneDayData.getLevels().get(hourIndex));
+                }
+            }
+        }
+        return batteryLevelMap.size() < MIN_SIZE ? null : new BatteryLevelData(batteryLevelMap);
+    }
+
+    /**
+     * 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) {
+        Preconditions.checkArgument(
+                timestampList.size() >= MIN_SIZE, "timestampList size:" + timestampList.size());
+        final List<Long> dailyTimestampList = new ArrayList<>();
+        final long startTimestamp = timestampList.get(0);
+        final long endTimestamp = timestampList.get(timestampList.size() - 1);
+        for (long timestamp = startTimestamp; timestamp < endTimestamp;
+                timestamp = TimestampUtils.getNextDayTimestamp(timestamp)) {
+            dailyTimestampList.add(timestamp);
+        }
+        dailyTimestampList.add(endTimestamp);
+        return dailyTimestampList;
+    }
+
+    private static List<List<Long>> getHourlyTimestamps(final List<Long> dailyTimestamps) {
+        final List<List<Long>> hourlyTimestamps = new ArrayList<>();
+        for (int dailyIndex = 0; dailyIndex < dailyTimestamps.size() - 1; dailyIndex++) {
+            final List<Long> hourlyTimestampsPerDay = new ArrayList<>();
+            final long startTime = dailyTimestamps.get(dailyIndex);
+            final long endTime = dailyTimestamps.get(dailyIndex + 1);
+
+            hourlyTimestampsPerDay.add(startTime);
+            for (long timestamp = TimestampUtils.getNextEvenHourTimestamp(startTime);
+                    timestamp < endTime; timestamp += TIME_SLOT) {
+                hourlyTimestampsPerDay.add(timestamp);
+            }
+            hourlyTimestampsPerDay.add(endTime);
+
+            hourlyTimestamps.add(hourlyTimestampsPerDay);
+        }
+        return hourlyTimestamps;
+    }
 }