/*
 * Copyright 2009 Google Inc.
 *
 * 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 de.dennisguse.opentracks.stats;

import android.util.Log;

import androidx.annotation.NonNull;
import androidx.annotation.VisibleForTesting;

import de.dennisguse.opentracks.content.data.TrackPoint;
import de.dennisguse.opentracks.content.data.TrackPointsColumns;
import de.dennisguse.opentracks.content.provider.TrackPointIterator;
import de.dennisguse.opentracks.util.LocationUtils;
import de.dennisguse.opentracks.util.TrackPointUtils;

/**
 * Updater for {@link TrackStatistics}.
 * For updating track {@link TrackStatistics} as new {@link TrackPoint}s are added.
 * NOTE: Some of the locations represent pause/resume separator.
 * NOTE: Has still support for segments (at the moment unused).
 *
 * @author Sandor Dornbush
 * @author Rodrigo Damazio
 */
public class TrackStatisticsUpdater {

    /**
     * The number of elevation readings to smooth to get a somewhat accurate signal.
     */
    @VisibleForTesting
    private static final int ELEVATION_SMOOTHING_FACTOR = 25;

    /**
     * The number of speed reading to smooth to get a somewhat accurate signal.
     */
    @VisibleForTesting
    private static final int SPEED_SMOOTHING_FACTOR = 25;

    private static final String TAG = TrackStatisticsUpdater.class.getSimpleName();
    /**
     * Ignore any acceleration faster than this.
     * Will ignore any speeds that imply acceleration greater than 2g's
     * 2g = 19.6 m/s^2 = 0.0002 m/ms^2 = 0.02 m/(m*ms)
     */
    private static final double MAX_ACCELERATION = 0.02;

    // The track's statistics
    private final TrackStatistics trackStatistics;

    // A buffer of the recent elevation readings (m)
    private final DoubleBuffer elevationBuffer_m = new DoubleBuffer(ELEVATION_SMOOTHING_FACTOR);
    // A buffer of the recent speed readings (m/s) for calculating max speed
    private final DoubleBuffer speedBuffer_ms = new DoubleBuffer(SPEED_SMOOTHING_FACTOR);

    // The current segment's statistics
    private TrackStatistics currentSegment;
    // Current segment's last trackPoint
    private TrackPoint lastTrackPoint;
    // Current segment's last moving trackPoint
    private TrackPoint lastMovingTrackPoint;

    /**
     * Creates a new {@link TrackStatisticsUpdater}.
     *
     * @param startTime_ms the start time in milliseconds
     */
    public TrackStatisticsUpdater(long startTime_ms) {
        trackStatistics = init(startTime_ms);
        currentSegment = init(startTime_ms);
    }

    /**
     * Creates a new{@link TrackStatisticsUpdater} with a {@link TrackStatisticsUpdater} already existed.
     *
     * @param trackStatistics a {@link TrackStatisticsUpdater}
     */
    public TrackStatisticsUpdater(TrackStatistics trackStatistics) {
        this.trackStatistics = trackStatistics;
        currentSegment = init(System.currentTimeMillis());
    }

    public void updateTime(long time) {
        currentSegment.setStopTime_ms(time);
        currentSegment.setTotalTime(time - currentSegment.getStartTime_ms());
    }

    /**
     * Gets the track's statistics.
     */
    public TrackStatistics getTrackStatistics() {
        // Take a snapshot - we don't want anyone messing with our trackStatistics
        TrackStatistics stats = new TrackStatistics(trackStatistics);
        stats.merge(currentSegment);
        return stats;
    }

    /**
     * Adds a trackPoint.
     * TODO: This assume trackPoint has a valid time.
     *
     * @param trackPoint             the trackPoint
     * @param minRecordingDistance the min recording distance
     */
    public void addTrackPoint(TrackPoint trackPoint, int minRecordingDistance) {
        // Always update time
        updateTime(trackPoint.getTime());
        if (!LocationUtils.isValidLocation(trackPoint.getLocation())) {
            // Either pause or resume marker
            if (trackPoint.getLatitude() == TrackPointsColumns.PAUSE_LATITUDE) {
                if (lastTrackPoint != null && lastMovingTrackPoint != null && lastTrackPoint != lastMovingTrackPoint) {
                    currentSegment.addTotalDistance(lastMovingTrackPoint.distanceTo(lastTrackPoint));
                }
                trackStatistics.merge(currentSegment);
            }
            currentSegment = init(trackPoint.getTime());
            lastTrackPoint = null;
            lastMovingTrackPoint = null;
            elevationBuffer_m.reset();
            speedBuffer_ms.reset();
            return;
        }

        //TODO Use Barometer to compute elevation gain.
        double elevationDifference = trackPoint.hasAltitude() ? updateElevation(trackPoint.getAltitude()) : 0.0;

        if (lastTrackPoint == null || lastMovingTrackPoint == null) {
            lastTrackPoint = trackPoint;
            lastMovingTrackPoint = trackPoint;
            return;
        }

        double movingDistance = lastMovingTrackPoint.distanceTo(trackPoint);
        if (movingDistance < minRecordingDistance && !TrackPointUtils.isMoving(trackPoint)) {
            speedBuffer_ms.reset();
            lastTrackPoint = trackPoint;
            return;
        }
        long movingTime = trackPoint.getTime() - lastTrackPoint.getTime();
        if (movingTime < 0) {
            lastTrackPoint = trackPoint;
            return;
        }

        // Update total distance
        currentSegment.addTotalDistance(movingDistance);

        // Update moving time
        currentSegment.addMovingTime(movingTime);

        // Update max speed
        if (trackPoint.hasSpeed() && lastTrackPoint.hasSpeed()) {
            updateSpeed(trackPoint, lastTrackPoint);
        }

        lastTrackPoint = trackPoint;
        lastMovingTrackPoint = trackPoint;
    }

    public void addTrackPoint(TrackPointIterator iterator, int minRecordingDistance) {
        while (iterator.hasNext()) {
            TrackPoint location = iterator.next();
            addTrackPoint(location, minRecordingDistance);
        }
    }

    /**
     * Gets the smoothed elevation over several readings.
     * The elevation readings is noisy so the smoothed elevation is better than the raw elevation for many tasks.
     */
    public double getSmoothedElevation() {
        return elevationBuffer_m.getAverage();
    }

    public double getSmoothedSpeed() {
        return speedBuffer_ms.getAverage();
    }

    /**
     * Updates a speed reading while assuming the user is moving.
     */
    @VisibleForTesting
    private void updateSpeed(@NonNull TrackPoint trackPoint, @NonNull TrackPoint lastTrackPoint) {
        if (!TrackPointUtils.isMoving(trackPoint)) {
            speedBuffer_ms.reset();
        } else if (isValidSpeed(trackPoint, lastTrackPoint)) {
            speedBuffer_ms.setNext(trackPoint.getSpeed());
            if (speedBuffer_ms.getAverage() > currentSegment.getMaxSpeed()) {
                currentSegment.setMaxSpeed(speedBuffer_ms.getAverage());
            }
        } else {
            Log.d(TAG, "Invalid speed. speed: " + trackPoint.getSpeed() + " lastLocationSpeed: " + lastTrackPoint.getSpeed());
        }
    }

    /**
     * Updates an elevation reading. Returns the difference.
     *
     * @param elevation the elevation
     */
    @VisibleForTesting
    private double updateElevation(double elevation) {
        // Update elevation using the smoothed average
        double oldAverage = elevationBuffer_m.getAverage();
        elevationBuffer_m.setNext(elevation);
        double newAverage = elevationBuffer_m.getAverage();

        currentSegment.updateElevationExtremities(newAverage);
        double difference = newAverage - oldAverage;
        if (difference > 0) {
            currentSegment.addTotalElevationGain(difference);
        }
        return difference;
    }

    private TrackStatistics init(long time) {
        TrackStatistics stats = new TrackStatistics();
        stats.setStartTime_ms(time);
        stats.setStopTime_ms(time);
        return stats;
    }

    /**
     * Returns true if the speed is valid.
     */
    private boolean isValidSpeed(@NonNull TrackPoint trackPoint, @NonNull TrackPoint lastTrackPoint) {
        // There are a lot of noisy speed readings. Do the cheapest checks first, most expensive last.
        if (trackPoint.getSpeed() == 0) {
            return false;
        }

        // The following code will ignore unlikely readings. 128 m/s seems to be an internal android error code.
        if (Math.abs(trackPoint.getSpeed() - 128) < 1) {
            return false;
        }

        // See if the speed seems physically likely. Ignore any speeds that imply acceleration greater than 2g.
        long timeDifference = trackPoint.getTime() - lastTrackPoint.getTime();
        double speedDifference = Math.abs(lastTrackPoint.getSpeed() - trackPoint.getSpeed());
        if (speedDifference > MAX_ACCELERATION * timeDifference) {
            return false;
        }

        // Only check if the speed buffer is full. Check that the speed is less than 10X the smoothed average and the speed difference doesn't imply 2g acceleration.
        if (speedBuffer_ms.isFull()) {
            double average = speedBuffer_ms.getAverage();
            double diff = Math.abs(average - trackPoint.getSpeed());
            return (trackPoint.getSpeed() < average * 10) && (diff < MAX_ACCELERATION * timeDifference);
        }

        return true;
    }
}