/*
 * Copyright (C) 2015 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.incallui.answer.impl.classifier;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.view.MotionEvent;
import java.util.concurrent.TimeUnit;

/**
 * A classifier which looks at the proximity sensor during the gesture. It calculates the percentage
 * the proximity sensor showing the near state during the whole gesture
 */
class ProximityClassifier extends GestureClassifier {
  private long gestureStartTimeNano;
  private long nearStartTimeNano;
  private long nearDuration;
  private boolean near;
  private float averageNear;

  public ProximityClassifier(ClassifierData classifierData) {}

  @Override
  public String getTag() {
    return "PROX";
  }

  @Override
  public void onSensorChanged(SensorEvent event) {
    if (event.sensor.getType() == Sensor.TYPE_PROXIMITY) {
      update(event.values[0] < event.sensor.getMaximumRange(), event.timestamp);
    }
  }

  @Override
  public void onTouchEvent(MotionEvent event) {
    int action = event.getActionMasked();

    if (action == MotionEvent.ACTION_DOWN) {
      gestureStartTimeNano = TimeUnit.MILLISECONDS.toNanos(event.getEventTime());
      nearStartTimeNano = TimeUnit.MILLISECONDS.toNanos(event.getEventTime());
      nearDuration = 0;
    }

    if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) {
      update(near, TimeUnit.MILLISECONDS.toNanos(event.getEventTime()));
      long duration = TimeUnit.MILLISECONDS.toNanos(event.getEventTime()) - gestureStartTimeNano;

      if (duration == 0) {
        averageNear = near ? 1.0f : 0.0f;
      } else {
        averageNear = (float) nearDuration / (float) duration;
      }
    }
  }

  /**
   * @param near is the sensor showing the near state right now
   * @param timestampNano time of this event in nanoseconds
   */
  private void update(boolean near, long timestampNano) {
    // This if is necessary because MotionEvents and SensorEvents do not come in
    // chronological order
    if (timestampNano > nearStartTimeNano) {
      // if the state before was near then add the difference of the current time and
      // mNearStartTimeNano to mNearDuration.
      if (this.near) {
        nearDuration += timestampNano - nearStartTimeNano;
      }

      // if the new state is near, set mNearStartTimeNano equal to this moment.
      if (near) {
        nearStartTimeNano = timestampNano;
      }
    }
    this.near = near;
  }

  @Override
  public float getFalseTouchEvaluation() {
    return ProximityEvaluator.evaluate(averageNear);
  }
}