Merge "Let scorers fine-tune scoring heuristics." into lmp-mr1-dev

 * A curve defining the network score over a range of RSSI values.

 *

 * <p>For each RSSI bucket, the score may be any byte. Scores have no absolute meaning and are only

 * considered relative to other scores assigned by the same scorer. Networks with no score are all

 * considered equivalent and ranked below any network with a score.

 * considered relative to other scores assigned by the same scorer. Networks with no score are

 * treated equivalently to a network with score {@link Byte#MIN_VALUE}, and will not be used.

 *

 * <p>For example, consider a curve starting at -110 dBm with a bucket width of 10 and the

 * following buckets: {@code [-20, -10, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]}.

 */

@SystemApi

public class RssiCurve implements Parcelable {

    private static final int DEFAULT_ACTIVE_NETWORK_RSSI_BOOST = 25;

    /** The starting dBm of the curve. */

    public final int start;

    /** The score for each RSSI bucket. */

    public final byte[] rssiBuckets;

    /**

     * The RSSI boost to give this network when active, in dBm.

     *

     * <p>When the system is connected to this network, it will pretend that the network has this

     * much higher of an RSSI. This is to avoid switching networks when another network has only a

     * slightly higher score.

     */

    public final int activeNetworkRssiBoost;

    /**

     * Construct a new {@link RssiCurve}.

     *

     * @param rssiBuckets the score for each RSSI bucket.

     */

    public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets) {

        this(start, bucketWidth, rssiBuckets, DEFAULT_ACTIVE_NETWORK_RSSI_BOOST);

    }

    /**

     * Construct a new {@link RssiCurve}.

     *

     * @param start the starting dBm of the curve.

     * @param bucketWidth the width of each RSSI bucket, in dBm.

     * @param rssiBuckets the score for each RSSI bucket.

     * @param activeNetworkRssiBoost the RSSI boost to apply when this network is active, in dBm.

     */

    public RssiCurve(int start, int bucketWidth, byte[] rssiBuckets, int activeNetworkRssiBoost) {

        this.start = start;

        this.bucketWidth = bucketWidth;

        if (rssiBuckets == null || rssiBuckets.length == 0) {

            throw new IllegalArgumentException("rssiBuckets must be at least one element large.");

        }

        this.rssiBuckets = rssiBuckets;

        this.activeNetworkRssiBoost = activeNetworkRssiBoost;

    }

    private RssiCurve(Parcel in) {

        int bucketCount = in.readInt();

        rssiBuckets = new byte[bucketCount];

        in.readByteArray(rssiBuckets);

        activeNetworkRssiBoost = in.readInt();

    }

    @Override

        out.writeInt(bucketWidth);

        out.writeInt(rssiBuckets.length);

        out.writeByteArray(rssiBuckets);

        out.writeInt(activeNetworkRssiBoost);

    }

    /**

     * @return the score for the given RSSI.

     */

    public byte lookupScore(int rssi) {

        return lookupScore(rssi, false /* isActiveNetwork */);

    }

    /**

     * Lookup the score for a given RSSI value.

     *

     * @param rssi The RSSI to lookup. If the RSSI falls below the start of the curve, the score at

     *         the start of the curve will be returned. If it falls after the end of the curve, the

     *         score at the end of the curve will be returned.

     * @param isActiveNetwork Whether this network is currently active.

     * @return the score for the given RSSI.

     */

    public byte lookupScore(int rssi, boolean isActiveNetwork) {

        if (isActiveNetwork) {

            rssi += activeNetworkRssiBoost;

        }

        int index = (rssi - start) / bucketWidth;

        // Snap the index to the closest bucket if it falls outside the curve.

        return start == rssiCurve.start &&

                bucketWidth == rssiCurve.bucketWidth &&

                Arrays.equals(rssiBuckets, rssiCurve.rssiBuckets);

                Arrays.equals(rssiBuckets, rssiCurve.rssiBuckets) &&

                activeNetworkRssiBoost == rssiCurve.activeNetworkRssiBoost;

    }

    @Override

    public int hashCode() {

        return Objects.hash(start, bucketWidth, rssiBuckets);

        return Objects.hash(start, bucketWidth, rssiBuckets, activeNetworkRssiBoost);

    }

    @Override

        sb.append("RssiCurve[start=")

                .append(start)

                .append(",bucketWidth=")

                .append(bucketWidth);

                .append(bucketWidth)

                .append(",activeNetworkRssiBoost=")

                .append(activeNetworkRssiBoost);

        sb.append(",buckets=");

        for (int i = 0; i < rssiBuckets.length; i++) {