content: /*
   * Copyright (C) 2014 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.net;
  
  import android.annotation.SystemApi;
  import android.os.Parcel;
  import android.os.Parcelable;
  
  import java.util.Arrays;
  import java.util.Objects;
  
  /**
   * 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
   * 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]}.
   * This represents a linear curve between -110 dBm and 30 dBm. It scores progressively higher at
   * stronger signal strengths.
   *
   * <p>A network can be assigned a fixed score independent of RSSI by setting
   * {@link #rssiBuckets} to a one-byte array whose element is the fixed score. {@link #start}
   * should be set to the lowest RSSI value at which this fixed score should apply, and
   * {@link #bucketWidth} should be set such that {@code start + bucketWidth} is equal to the
   * highest RSSI value at which this fixed score should apply.
   *
   * <p>Note that RSSI values below -110 dBm or above 30 dBm are unlikely to cause any difference
   * in connectivity behavior from those endpoints. That is, the connectivity framework will treat
   * a network with a -120 dBm signal exactly as it would treat one with a -110 dBm signal.
   * Therefore, graphs which specify scores outside this range may be truncated to this range by
   * the system.
   *
   * @see ScoredNetwork
   * @hide
   */
  @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 width of each RSSI bucket, in dBm. */
      public final int bucketWidth;
  
      /** 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 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.
       */
      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) {
          start = in.readInt();
          bucketWidth = in.readInt();
          int bucketCount = in.readInt();
          rssiBuckets = new byte[bucketCount];
          in.readByteArray(rssiBuckets);
          activeNetworkRssiBoost = in.readInt();
      }
  
      @Override
      public int describeContents() {
          return 0;
      }
  
      @Override
      public void writeToParcel(Parcel out, int flags) {
          out.writeInt(start);
          out.writeInt(bucketWidth);
          out.writeInt(rssiBuckets.length);
          out.writeByteArray(rssiBuckets);
          out.writeInt(activeNetworkRssiBoost);
      }
  
      /**
       * 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.
       * @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.
          if (index < 0) {
              index = 0;
          } else if (index > rssiBuckets.length - 1) {
              index = rssiBuckets.length - 1;
          }
  
          return rssiBuckets[index];
      }
  
      /**
       * Determine if two RSSI curves are defined in the same way.
       *
       * <p>Note that two curves can be equivalent but defined differently, e.g. if one bucket in one
       * curve is split into two buckets in another. For the purpose of this method, these curves are
       * not considered equal to each other.
       */
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
  
          RssiCurve rssiCurve = (RssiCurve) o;
  
          return start == rssiCurve.start &&
                  bucketWidth == rssiCurve.bucketWidth &&
                  Arrays.equals(rssiBuckets, rssiCurve.rssiBuckets) &&
                  activeNetworkRssiBoost == rssiCurve.activeNetworkRssiBoost;
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(start, bucketWidth, activeNetworkRssiBoost) ^ Arrays.hashCode(rssiBuckets);
      }
  
      @Override
      public String toString() {
          StringBuilder sb = new StringBuilder();
          sb.append("RssiCurve[start=")
                  .append(start)
                  .append(",bucketWidth=")
                  .append(bucketWidth)
                  .append(",activeNetworkRssiBoost=")
                  .append(activeNetworkRssiBoost);
  
          sb.append(",buckets=");
          for (int i = 0; i < rssiBuckets.length; i++) {
              sb.append(rssiBuckets[i]);
              if (i < rssiBuckets.length - 1) {
                  sb.append(",");
              }
          }
          sb.append("]");
  
          return sb.toString();
      }
  
      public static final @android.annotation.NonNull Creator<RssiCurve> CREATOR =
              new Creator<RssiCurve>() {
                  @Override
                  public RssiCurve createFromParcel(Parcel in) {
                      return new RssiCurve(in);
                  }
  
                  @Override
                  public RssiCurve[] newArray(int size) {
                      return new RssiCurve[size];
                  }
              };
  }
  