android/hardware/display/BrightnessConfiguration.java

/*
 * Copyright (C) 2017 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 android.hardware.display;

import android.annotation.FloatRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.SystemApi;
import android.annotation.TestApi;
import android.content.pm.ApplicationInfo;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.Pair;

import com.android.internal.util.Preconditions;
import com.android.internal.util.XmlUtils;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlSerializer;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;

/** @hide */
@SystemApi
@TestApi
public final class BrightnessConfiguration implements Parcelable {
    private static final String TAG_BRIGHTNESS_CURVE = "brightness-curve";
    private static final String TAG_BRIGHTNESS_POINT = "brightness-point";
    private static final String TAG_BRIGHTNESS_CORRECTIONS = "brightness-corrections";
    private static final String TAG_BRIGHTNESS_CORRECTION = "brightness-correction";
    private static final String TAG_BRIGHTNESS_PARAMS = "brightness-params";
    private static final String ATTR_LUX = "lux";
    private static final String ATTR_NITS = "nits";
    private static final String ATTR_DESCRIPTION = "description";
    private static final String ATTR_PACKAGE_NAME = "package-name";
    private static final String ATTR_CATEGORY = "category";
    private static final String ATTR_COLLECT_COLOR = "collect-color";
    private static final String ATTR_MODEL_TIMEOUT = "model-timeout";
    private static final String ATTR_MODEL_LOWER_BOUND = "model-lower-bound";
    private static final String ATTR_MODEL_UPPER_BOUND = "model-upper-bound";
    /**
     * Returned from {@link #getShortTermModelTimeoutMillis()} if no timeout has been set.
     * In this case the device will use the default timeout available in the
     * {@link BrightnessConfiguration} returned from
     * {@link DisplayManager#getDefaultBrightnessConfiguration()}.
     */
    public static final long SHORT_TERM_TIMEOUT_UNSET = -1;

    private final float[] mLux;
    private final float[] mNits;
    private final Map<String, BrightnessCorrection> mCorrectionsByPackageName;
    private final Map<Integer, BrightnessCorrection> mCorrectionsByCategory;
    private final String mDescription;
    private final boolean mShouldCollectColorSamples;
    private final long mShortTermModelTimeout;
    private final float mShortTermModelLowerLuxMultiplier;
    private final float mShortTermModelUpperLuxMultiplier;

    private BrightnessConfiguration(float[] lux, float[] nits,
            Map<String, BrightnessCorrection> correctionsByPackageName,
            Map<Integer, BrightnessCorrection> correctionsByCategory, String description,
            boolean shouldCollectColorSamples,
            long shortTermModelTimeout,
            float shortTermModelLowerLuxMultiplier,
            float shortTermModelUpperLuxMultiplier) {
        mLux = lux;
        mNits = nits;
        mCorrectionsByPackageName = correctionsByPackageName;
        mCorrectionsByCategory = correctionsByCategory;
        mDescription = description;
        mShouldCollectColorSamples = shouldCollectColorSamples;
        mShortTermModelTimeout = shortTermModelTimeout;
        mShortTermModelLowerLuxMultiplier = shortTermModelLowerLuxMultiplier;
        mShortTermModelUpperLuxMultiplier = shortTermModelUpperLuxMultiplier;
    }

    /**
     * Gets the base brightness as curve.
     *
     * The curve is returned as a pair of float arrays, the first representing all of the lux
     * points of the brightness curve and the second representing all of the nits values of the
     * brightness curve.
     *
     * @return the control points for the brightness curve.
     */
    public Pair<float[], float[]> getCurve() {
        return Pair.create(Arrays.copyOf(mLux, mLux.length), Arrays.copyOf(mNits, mNits.length));
    }

    /**
     * Returns a brightness correction by app, or null.
     *
     * @param packageName
     *      The app's package name.
     *
     * @return The matching brightness correction, or null.
     *
     */
    @Nullable
    public BrightnessCorrection getCorrectionByPackageName(@NonNull String packageName) {
        return mCorrectionsByPackageName.get(packageName);
    }

    /**
     * Returns a brightness correction by app category, or null.
     *
     * @param category
     *      The app category.
     *
     * @return The matching brightness correction, or null.
     */
    @Nullable
    public BrightnessCorrection getCorrectionByCategory(@ApplicationInfo.Category int category) {
        return mCorrectionsByCategory.get(category);
    }

    /**
     * Returns description string.
     * @hide
     */
    public String getDescription() {
        return mDescription;
    }

    /**
     * Returns whether color samples should be collected in
     * {@link BrightnessChangeEvent#colorValueBuckets}.
     */
    public boolean shouldCollectColorSamples() {
        return mShouldCollectColorSamples;
    }

    /**
     * Returns the timeout for the short term model in milliseconds.
     *
     * If the screen is inactive for this timeout then the short term model
     * will check the lux range defined by {@link #getShortTermModelLowerLuxMultiplier()} and
     * {@link #getShortTermModelUpperLuxMultiplier()} to decide whether to keep any adjustment
     * the user has made to adaptive brightness.
     */
    public long getShortTermModelTimeoutMillis() {
        return mShortTermModelTimeout;
    }

    /**
     * Returns the multiplier used to calculate the upper bound for which
     * a users adaptive brightness is considered valid.
     *
     * For example if a user changes the brightness when the ambient light level
     * is 100 lux, the adjustment will be kept if the current ambient light level
     * is {@code <= 100 + (100 * getShortTermModelUpperLuxMultiplier())}.
     */
    public float getShortTermModelUpperLuxMultiplier() {
        return mShortTermModelUpperLuxMultiplier;
    }

    /**
     * Returns the multiplier used to calculate the lower bound for which
     * a users adaptive brightness is considered valid.
     *
     * For example if a user changes the brightness when the ambient light level
     * is 100 lux, the adjustment will be kept if the current ambient light level
     * is {@code >= 100 - (100 * getShortTermModelLowerLuxMultiplier())}.
     */
    public float getShortTermModelLowerLuxMultiplier() {
        return mShortTermModelLowerLuxMultiplier;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeFloatArray(mLux);
        dest.writeFloatArray(mNits);
        dest.writeInt(mCorrectionsByPackageName.size());
        for (Entry<String, BrightnessCorrection> entry : mCorrectionsByPackageName.entrySet()) {
            final String packageName = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            dest.writeString(packageName);
            correction.writeToParcel(dest, flags);
        }
        dest.writeInt(mCorrectionsByCategory.size());
        for (Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
            final int category = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            dest.writeInt(category);
            correction.writeToParcel(dest, flags);
        }
        dest.writeString(mDescription);
        dest.writeBoolean(mShouldCollectColorSamples);
        dest.writeLong(mShortTermModelTimeout);
        dest.writeFloat(mShortTermModelLowerLuxMultiplier);
        dest.writeFloat(mShortTermModelUpperLuxMultiplier);
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @NonNull
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder("BrightnessConfiguration{[");
        final int size = mLux.length;
        for (int i = 0; i < size; i++) {
            if (i != 0) {
                sb.append(", ");
            }
            sb.append("(").append(mLux[i]).append(", ").append(mNits[i]).append(")");
        }
        sb.append("], {");
        for (Entry<String, BrightnessCorrection> entry : mCorrectionsByPackageName.entrySet()) {
            sb.append("'" + entry.getKey() + "': " + entry.getValue() + ", ");
        }
        for (Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
            sb.append(entry.getKey() + ": " + entry.getValue() + ", ");
        }
        sb.append("}, '");
        if (mDescription != null) {
            sb.append(mDescription);
        }
        sb.append(", shouldCollectColorSamples = " + mShouldCollectColorSamples);
        if (mShortTermModelTimeout >= 0) {
            sb.append(", shortTermModelTimeout = " + mShortTermModelTimeout);
        }
        if (!Float.isNaN(mShortTermModelLowerLuxMultiplier)) {
            sb.append(", shortTermModelLowerLuxMultiplier = " + mShortTermModelLowerLuxMultiplier);
        }
        if (!Float.isNaN(mShortTermModelLowerLuxMultiplier)) {
            sb.append(", shortTermModelUpperLuxMultiplier = " + mShortTermModelUpperLuxMultiplier);
        }
        sb.append("'}");
        return sb.toString();
    }

    @Override
    public int hashCode() {
        int result = 1;
        result = result * 31 + Arrays.hashCode(mLux);
        result = result * 31 + Arrays.hashCode(mNits);
        result = result * 31 + mCorrectionsByPackageName.hashCode();
        result = result * 31 + mCorrectionsByCategory.hashCode();
        if (mDescription != null) {
            result = result * 31 + mDescription.hashCode();
        }
        result = result * 31 + Boolean.hashCode(mShouldCollectColorSamples);
        result = result * 31 + Long.hashCode(mShortTermModelTimeout);
        result = result * 31 + Float.hashCode(mShortTermModelLowerLuxMultiplier);
        result = result * 31 + Float.hashCode(mShortTermModelUpperLuxMultiplier);
        return result;
    }

    @Override
    public boolean equals(@Nullable Object o) {
        if (o == this) {
            return true;
        }
        if (!(o instanceof BrightnessConfiguration)) {
            return false;
        }
        final BrightnessConfiguration other = (BrightnessConfiguration) o;
        return Arrays.equals(mLux, other.mLux) && Arrays.equals(mNits, other.mNits)
                && mCorrectionsByPackageName.equals(other.mCorrectionsByPackageName)
                && mCorrectionsByCategory.equals(other.mCorrectionsByCategory)
                && Objects.equals(mDescription, other.mDescription)
                && mShouldCollectColorSamples == other.mShouldCollectColorSamples
                && mShortTermModelTimeout == other.mShortTermModelTimeout
                && checkFloatEquals(mShortTermModelLowerLuxMultiplier,
                    other.mShortTermModelLowerLuxMultiplier)
                && checkFloatEquals(mShortTermModelUpperLuxMultiplier,
                    other.mShortTermModelUpperLuxMultiplier);
    }

    private boolean checkFloatEquals(float one, float two) {
        if (Float.isNaN(one) && Float.isNaN(two)) {
            return true;
        }
        return one == two;
    }

    public static final @android.annotation.NonNull Creator<BrightnessConfiguration> CREATOR =
            new Creator<BrightnessConfiguration>() {
        public BrightnessConfiguration createFromParcel(Parcel in) {
            float[] lux = in.createFloatArray();
            float[] nits = in.createFloatArray();
            Builder builder = new Builder(lux, nits);

            int n = in.readInt();
            for (int i = 0; i < n; i++) {
                final String packageName = in.readString();
                final BrightnessCorrection correction =
                        BrightnessCorrection.CREATOR.createFromParcel(in);
                builder.addCorrectionByPackageName(packageName, correction);
            }

            n = in.readInt();
            for (int i = 0; i < n; i++) {
                final int category = in.readInt();
                final BrightnessCorrection correction =
                        BrightnessCorrection.CREATOR.createFromParcel(in);
                builder.addCorrectionByCategory(category, correction);
            }

            final String description = in.readString();
            builder.setDescription(description);
            final boolean shouldCollectColorSamples = in.readBoolean();
            builder.setShouldCollectColorSamples(shouldCollectColorSamples);
            builder.setShortTermModelTimeoutMillis(in.readLong());
            builder.setShortTermModelLowerLuxMultiplier(in.readFloat());
            builder.setShortTermModelUpperLuxMultiplier(in.readFloat());
            return builder.build();
        }

        public BrightnessConfiguration[] newArray(int size) {
            return new BrightnessConfiguration[size];
        }
    };

    /**
     * Writes the configuration to an XML serializer.
     *
     * @param serializer
     *      The XML serializer.
     *
     * @hide
     */
    public void saveToXml(@NonNull XmlSerializer serializer) throws IOException {
        serializer.startTag(null, TAG_BRIGHTNESS_CURVE);
        if (mDescription != null) {
            serializer.attribute(null, ATTR_DESCRIPTION, mDescription);
        }
        for (int i = 0; i < mLux.length; i++) {
            serializer.startTag(null, TAG_BRIGHTNESS_POINT);
            serializer.attribute(null, ATTR_LUX, Float.toString(mLux[i]));
            serializer.attribute(null, ATTR_NITS, Float.toString(mNits[i]));
            serializer.endTag(null, TAG_BRIGHTNESS_POINT);
        }
        serializer.endTag(null, TAG_BRIGHTNESS_CURVE);

        serializer.startTag(null, TAG_BRIGHTNESS_CORRECTIONS);
        for (Map.Entry<String, BrightnessCorrection> entry :
                mCorrectionsByPackageName.entrySet()) {
            final String packageName = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            serializer.startTag(null, TAG_BRIGHTNESS_CORRECTION);
            serializer.attribute(null, ATTR_PACKAGE_NAME, packageName);
            correction.saveToXml(serializer);
            serializer.endTag(null, TAG_BRIGHTNESS_CORRECTION);
        }
        for (Map.Entry<Integer, BrightnessCorrection> entry : mCorrectionsByCategory.entrySet()) {
            final int category = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            serializer.startTag(null, TAG_BRIGHTNESS_CORRECTION);
            serializer.attribute(null, ATTR_CATEGORY, Integer.toString(category));
            correction.saveToXml(serializer);
            serializer.endTag(null, TAG_BRIGHTNESS_CORRECTION);
        }
        serializer.endTag(null, TAG_BRIGHTNESS_CORRECTIONS);

        serializer.startTag(null, TAG_BRIGHTNESS_PARAMS);
        if (mShouldCollectColorSamples) {
            serializer.attribute(null, ATTR_COLLECT_COLOR, Boolean.toString(true));
        }
        if (mShortTermModelTimeout >= 0) {
            serializer.attribute(null, ATTR_MODEL_TIMEOUT,
                    Long.toString(mShortTermModelTimeout));
        }
        if (!Float.isNaN(mShortTermModelLowerLuxMultiplier)) {
            serializer.attribute(null, ATTR_MODEL_LOWER_BOUND,
                    Float.toString(mShortTermModelLowerLuxMultiplier));
        }
        if (!Float.isNaN(mShortTermModelUpperLuxMultiplier)) {
            serializer.attribute(null, ATTR_MODEL_UPPER_BOUND,
                    Float.toString(mShortTermModelUpperLuxMultiplier));
        }
        serializer.endTag(null, TAG_BRIGHTNESS_PARAMS);
    }

    /**
     * Read a configuration from an XML parser.
     *
     * @param parser
     *      The XML parser.
     *
     * @throws IOException
     *      The parser failed to read the XML file.
     * @throws XmlPullParserException
     *      The parser failed to parse the XML file.
     *
     * @hide
     */
    public static BrightnessConfiguration loadFromXml(@NonNull XmlPullParser parser)
            throws IOException, XmlPullParserException {
        String description = null;
        List<Float> luxList = new ArrayList<>();
        List<Float> nitsList = new ArrayList<>();
        Map<String, BrightnessCorrection> correctionsByPackageName = new HashMap<>();
        Map<Integer, BrightnessCorrection> correctionsByCategory = new HashMap<>();
        boolean shouldCollectColorSamples = false;
        long shortTermModelTimeout = SHORT_TERM_TIMEOUT_UNSET;
        float shortTermModelLowerLuxMultiplier = Float.NaN;
        float shortTermModelUpperLuxMultiplier = Float.NaN;
        final int configDepth = parser.getDepth();
        while (XmlUtils.nextElementWithin(parser, configDepth)) {
            if (TAG_BRIGHTNESS_CURVE.equals(parser.getName())) {
                description = parser.getAttributeValue(null, ATTR_DESCRIPTION);
                final int curveDepth = parser.getDepth();
                while (XmlUtils.nextElementWithin(parser, curveDepth)) {
                    if (!TAG_BRIGHTNESS_POINT.equals(parser.getName())) {
                        continue;
                    }
                    final float lux = loadFloatFromXml(parser, ATTR_LUX);
                    final float nits = loadFloatFromXml(parser, ATTR_NITS);
                    luxList.add(lux);
                    nitsList.add(nits);
                }
            } else if (TAG_BRIGHTNESS_CORRECTIONS.equals(parser.getName())) {
                final int correctionsDepth = parser.getDepth();
                while (XmlUtils.nextElementWithin(parser, correctionsDepth)) {
                    if (!TAG_BRIGHTNESS_CORRECTION.equals(parser.getName())) {
                        continue;
                    }
                    final String packageName = parser.getAttributeValue(null, ATTR_PACKAGE_NAME);
                    final String categoryText = parser.getAttributeValue(null, ATTR_CATEGORY);
                    BrightnessCorrection correction = BrightnessCorrection.loadFromXml(parser);
                    if (packageName != null) {
                        correctionsByPackageName.put(packageName, correction);
                    } else if (categoryText != null) {
                        try {
                            final int category = Integer.parseInt(categoryText);
                            correctionsByCategory.put(category, correction);
                        } catch (NullPointerException | NumberFormatException e) {
                            continue;
                        }
                    }
                }
            } else if (TAG_BRIGHTNESS_PARAMS.equals(parser.getName())) {
                shouldCollectColorSamples =
                        Boolean.parseBoolean(parser.getAttributeValue(null, ATTR_COLLECT_COLOR));
                Long timeout = loadLongFromXml(parser, ATTR_MODEL_TIMEOUT);
                if (timeout != null) {
                    shortTermModelTimeout = timeout;
                }
                shortTermModelLowerLuxMultiplier = loadFloatFromXml(parser, ATTR_MODEL_LOWER_BOUND);
                shortTermModelUpperLuxMultiplier = loadFloatFromXml(parser, ATTR_MODEL_UPPER_BOUND);
            }
        }
        final int n = luxList.size();
        float[] lux = new float[n];
        float[] nits = new float[n];
        for (int i = 0; i < n; i++) {
            lux[i] = luxList.get(i);
            nits[i] = nitsList.get(i);
        }
        final BrightnessConfiguration.Builder builder = new BrightnessConfiguration.Builder(lux,
                nits);
        builder.setDescription(description);
        for (Map.Entry<String, BrightnessCorrection> entry : correctionsByPackageName.entrySet()) {
            final String packageName = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            builder.addCorrectionByPackageName(packageName, correction);
        }
        for (Map.Entry<Integer, BrightnessCorrection> entry : correctionsByCategory.entrySet()) {
            final int category = entry.getKey();
            final BrightnessCorrection correction = entry.getValue();
            builder.addCorrectionByCategory(category, correction);
        }
        builder.setShouldCollectColorSamples(shouldCollectColorSamples);
        builder.setShortTermModelTimeoutMillis(shortTermModelTimeout);
        builder.setShortTermModelLowerLuxMultiplier(shortTermModelLowerLuxMultiplier);
        builder.setShortTermModelUpperLuxMultiplier(shortTermModelUpperLuxMultiplier);
        return builder.build();
    }

    private static float loadFloatFromXml(XmlPullParser parser, String attribute) {
        final String string = parser.getAttributeValue(null, attribute);
        try {
            return Float.parseFloat(string);
        } catch (NullPointerException | NumberFormatException e) {
            return Float.NaN;
        }
    }

    private static Long loadLongFromXml(XmlPullParser parser, String attribute) {
        final String string = parser.getAttributeValue(null, attribute);
        try {
            return Long.parseLong(string);
        } catch (NullPointerException | NumberFormatException e) {
            // Ignoring
        }
        return null;
    }

    /**
     * A builder class for {@link BrightnessConfiguration}s.
     */
    public static class Builder {
        private static final int MAX_CORRECTIONS_BY_PACKAGE_NAME = 20;
        private static final int MAX_CORRECTIONS_BY_CATEGORY = 20;

        private float[] mCurveLux;
        private float[] mCurveNits;
        private Map<String, BrightnessCorrection> mCorrectionsByPackageName;
        private Map<Integer, BrightnessCorrection> mCorrectionsByCategory;
        private String mDescription;
        private boolean mShouldCollectColorSamples;
        private long mShortTermModelTimeout = SHORT_TERM_TIMEOUT_UNSET;
        private float mShortTermModelLowerLuxMultiplier = Float.NaN;
        private float mShortTermModelUpperLuxMultiplier = Float.NaN;

        /**
         * Constructs the builder with the control points for the brightness curve.
         *
         * Brightness curves must have strictly increasing ambient brightness values in lux and
         * monotonically increasing display brightness values in nits. In addition, the initial
         * control point must be 0 lux.
         *
         * @throws IllegalArgumentException if the initial control point is not at 0 lux.
         * @throws IllegalArgumentException if the lux levels are not strictly increasing.
         * @throws IllegalArgumentException if the nit levels are not monotonically increasing.
         */
        public Builder(float[] lux, float[] nits) {
            Objects.requireNonNull(lux);
            Objects.requireNonNull(nits);
            if (lux.length == 0 || nits.length == 0) {
                throw new IllegalArgumentException("Lux and nits arrays must not be empty");
            }
            if (lux.length != nits.length) {
                throw new IllegalArgumentException("Lux and nits arrays must be the same length");
            }
            if (lux[0] != 0) {
                throw new IllegalArgumentException("Initial control point must be for 0 lux");
            }
            Preconditions.checkArrayElementsInRange(lux, 0, Float.MAX_VALUE, "lux");
            Preconditions.checkArrayElementsInRange(nits, 0, Float.MAX_VALUE, "nits");
            checkMonotonic(lux, true /*strictly increasing*/, "lux");
            checkMonotonic(nits, false /*strictly increasing*/, "nits");
            mCurveLux = lux;
            mCurveNits = nits;
            mCorrectionsByPackageName = new HashMap<>();
            mCorrectionsByCategory = new HashMap<>();
        }

        /**
         * Returns the maximum number of corrections by package name allowed.
         *
         * @return The maximum number of corrections by package name allowed.
         *
         */
        public int getMaxCorrectionsByPackageName() {
            return MAX_CORRECTIONS_BY_PACKAGE_NAME;
        }

        /**
         * Returns the maximum number of corrections by category allowed.
         *
         * @return The maximum number of corrections by category allowed.
         *
         */
        public int getMaxCorrectionsByCategory() {
            return MAX_CORRECTIONS_BY_CATEGORY;
        }

        /**
         * Add a brightness correction by app package name.
         * This correction is applied whenever an app with this package name has the top activity
         * of the focused stack.
         *
         * @param packageName
         *      The app's package name.
         * @param correction
         *      The brightness correction.
         *
         * @return The builder.
         *
         * @throws IllegalArgumentExceptions
         *      Maximum number of corrections by package name exceeded (see
         *      {@link #getMaxCorrectionsByPackageName}).
         *
         */
        @NonNull
        public Builder addCorrectionByPackageName(@NonNull String packageName,
                @NonNull BrightnessCorrection correction) {
            Objects.requireNonNull(packageName, "packageName must not be null");
            Objects.requireNonNull(correction, "correction must not be null");
            if (mCorrectionsByPackageName.size() >= getMaxCorrectionsByPackageName()) {
                throw new IllegalArgumentException("Too many corrections by package name");
            }
            mCorrectionsByPackageName.put(packageName, correction);
            return this;
        }

        /**
         * Add a brightness correction by app category.
         * This correction is applied whenever an app with this category has the top activity of
         * the focused stack, and only if a correction by package name has not been applied.
         *
         * @param category
         *      The {@link android.content.pm.ApplicationInfo#category app category}.
         * @param correction
         *      The brightness correction.
         *
         * @return The builder.
         *
         * @throws IllegalArgumentException
         *      Maximum number of corrections by category exceeded (see
         *      {@link #getMaxCorrectionsByCategory}).
         *
         */
        @NonNull
        public Builder addCorrectionByCategory(@ApplicationInfo.Category int category,
                @NonNull BrightnessCorrection correction) {
            Objects.requireNonNull(correction, "correction must not be null");
            if (mCorrectionsByCategory.size() >= getMaxCorrectionsByCategory()) {
                throw new IllegalArgumentException("Too many corrections by category");
            }
            mCorrectionsByCategory.put(category, correction);
            return this;
        }

        /**
         * Set description of the brightness curve.
         *
         * @param description brief text describing the curve pushed. It maybe truncated
         *                    and will not be displayed in the UI
         */
        @NonNull
        public Builder setDescription(@Nullable String description) {
            mDescription = description;
            return this;
        }

        /**
         * Control whether screen color samples should be returned in
         * {@link BrightnessChangeEvent#colorValueBuckets} if supported by the device.
         *
         * @param shouldCollectColorSamples true if color samples should be collected.
         * @return
         */
        @NonNull
        public Builder setShouldCollectColorSamples(boolean shouldCollectColorSamples) {
            mShouldCollectColorSamples = shouldCollectColorSamples;
            return this;
        }

        /**
         * Sets the timeout for the short term model in milliseconds.
         *
         * If the screen is inactive for this timeout then the short term model
         * will check the lux range defined by {@link #setShortTermModelLowerLuxMultiplier(float))}
         * and {@link #setShortTermModelUpperLuxMultiplier(float)} to decide whether to keep any
         * adjustment the user has made to adaptive brightness.
         */
        @NonNull
        public Builder setShortTermModelTimeoutMillis(long shortTermModelTimeoutMillis) {
            mShortTermModelTimeout = shortTermModelTimeoutMillis;
            return this;
        }

        /**
         * Sets the multiplier used to calculate the upper bound for which
         * a users adaptive brightness is considered valid.
         *
         * For example if a user changes the brightness when the ambient light level
         * is 100 lux, the adjustment will be kept if the current ambient light level
         * is {@code <= 100 + (100 * shortTermModelUpperLuxMultiplier)}.
         *
         * @throws IllegalArgumentException if shortTermModelUpperLuxMultiplier is negative.
         */
        @NonNull
        public Builder setShortTermModelUpperLuxMultiplier(
                @FloatRange(from = 0.0f) float shortTermModelUpperLuxMultiplier) {
            if (shortTermModelUpperLuxMultiplier < 0.0f) {
                throw new IllegalArgumentException("Negative lux multiplier");
            }
            mShortTermModelUpperLuxMultiplier = shortTermModelUpperLuxMultiplier;
            return this;
        }

        /**
         * Returns the multiplier used to calculate the lower bound for which
         * a users adaptive brightness is considered valid.
         *
         * For example if a user changes the brightness when the ambient light level
         * is 100 lux, the adjustment will be kept if the current ambient light level
         * is {@code >= 100 - (100 * shortTermModelLowerLuxMultiplier)}.
         *
         * @throws IllegalArgumentException if shortTermModelUpperLuxMultiplier is negative.
         */
        @NonNull
        public Builder setShortTermModelLowerLuxMultiplier(
                @FloatRange(from = 0.0f) float shortTermModelLowerLuxMultiplier) {
            if (shortTermModelLowerLuxMultiplier < 0.0f) {
                throw new IllegalArgumentException("Negative lux multiplier");
            }
            mShortTermModelLowerLuxMultiplier = shortTermModelLowerLuxMultiplier;
            return this;
        }

        /**
         * Builds the {@link BrightnessConfiguration}.
         */
        @NonNull
        public BrightnessConfiguration build() {
            if (mCurveLux == null || mCurveNits == null) {
                throw new IllegalStateException("A curve must be set!");
            }
            return new BrightnessConfiguration(mCurveLux, mCurveNits, mCorrectionsByPackageName,
                    mCorrectionsByCategory, mDescription, mShouldCollectColorSamples,
                    mShortTermModelTimeout, mShortTermModelLowerLuxMultiplier,
                    mShortTermModelUpperLuxMultiplier);
        }

        private static void checkMonotonic(float[] vals, boolean strictlyIncreasing, String name) {
            if (vals.length <= 1) {
                return;
            }
            float prev = vals[0];
            for (int i = 1; i < vals.length; i++) {
                if (prev > vals[i] || prev == vals[i] && strictlyIncreasing) {
                    String condition = strictlyIncreasing ? "strictly increasing" : "monotonic";
                    throw new IllegalArgumentException(name + " values must be " + condition);
                }
                prev = vals[i];
            }
        }
    }
}