package com.imranmentese.reactnativenetwatch.shake;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;

import androidx.annotation.Nullable;

import com.facebook.infer.annotation.Assertions;

import java.util.concurrent.TimeUnit;

public class CustomShakeDetector implements SensorEventListener {

    //only record and consider the last MAX_SAMPLES number of data points
    private static final int MAX_SAMPLES = 40;
    //collect sensor data in this interval (nanoseconds)
    private static final long MIN_TIME_BETWEEN_SAMPLES_NS =
            TimeUnit.NANOSECONDS.convert(20, TimeUnit.MILLISECONDS);
    //expected duration of one shake in nanoseconds
    private static final long VISIBLE_TIME_RANGE_NS =
            TimeUnit.NANOSECONDS.convert(250, TimeUnit.MILLISECONDS);
    //minimum amount of force on accelerometer sensor to constitute a shake
    private static final int MAGNITUDE_THRESHOLD = 25;
    //this percentage of data points must have at least the force of MAGNITUDE_THRESHOLD
    private static final int PERCENT_OVER_THRESHOLD_FOR_SHAKE = 60;
    //number of nanoseconds to listen for and count shakes
    private static final float SHAKING_WINDOW_NS =
            TimeUnit.NANOSECONDS.convert(3, TimeUnit.SECONDS);

    public static interface ShakeListener {
        void onShake();
    }

    private final ShakeListener mShakeListener;

    @Nullable
    private SensorManager mSensorManager;
    private long mLastTimestamp;
    private int mCurrentIndex;
    private int mNumShakes;
    private long mLastShakeTimestamp;
    @Nullable private double[] mMagnitudes;
    @Nullable private long[] mTimestamps;
    //number of shakes required to trigger onShake()
    private int mMinNumShakes;

    public CustomShakeDetector(ShakeListener listener) {
        this(listener, 1);
    }

    public CustomShakeDetector(ShakeListener listener, int minNumShakes) {
        mShakeListener = listener;
        mMinNumShakes = minNumShakes;
    }

    /**
     * Start listening for shakes.
     */
    public void start(SensorManager manager) {
        Assertions.assertNotNull(manager);
        Sensor accelerometer = manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        if (accelerometer != null) {
            mSensorManager = manager;
            mLastTimestamp = -1;
            mCurrentIndex = 0;
            mMagnitudes = new double[MAX_SAMPLES];
            mTimestamps = new long[MAX_SAMPLES];
            mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_UI);
            mNumShakes = 0;
            mLastShakeTimestamp = 0;
        }
    }

    /**
     * Stop listening for shakes.
     */
    public void stop() {
        if (mSensorManager != null) {
            mSensorManager.unregisterListener(this);
            mSensorManager = null;
        }
    }

    @Override
    public void onSensorChanged(SensorEvent sensorEvent) {
        if (sensorEvent.timestamp - mLastTimestamp < MIN_TIME_BETWEEN_SAMPLES_NS) {
            return;
        }

        Assertions.assertNotNull(mTimestamps);
        Assertions.assertNotNull(mMagnitudes);

        float ax = sensorEvent.values[0];
        float ay = sensorEvent.values[1];
        float az = sensorEvent.values[2];

        mLastTimestamp = sensorEvent.timestamp;
        mTimestamps[mCurrentIndex] = sensorEvent.timestamp;
        mMagnitudes[mCurrentIndex] = Math.sqrt(ax * ax + ay * ay + az * az);

        maybeDispatchShake(sensorEvent.timestamp);

        mCurrentIndex = (mCurrentIndex + 1) % MAX_SAMPLES;
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int i) {
    }

    private void maybeDispatchShake(long currentTimestamp) {
        Assertions.assertNotNull(mTimestamps);
        Assertions.assertNotNull(mMagnitudes);

        int numOverThreshold = 0;
        int total = 0;
        for (int i = 0; i < MAX_SAMPLES; i++) {
            int index = (mCurrentIndex - i + MAX_SAMPLES) % MAX_SAMPLES;
            if (currentTimestamp - mTimestamps[index] < VISIBLE_TIME_RANGE_NS) {
                total++;
                if (mMagnitudes[index] >= MAGNITUDE_THRESHOLD) {
                    numOverThreshold++;
                }
            }
        }
        if (((double) numOverThreshold) / total > PERCENT_OVER_THRESHOLD_FOR_SHAKE / 100.0) {
            if (currentTimestamp - mLastShakeTimestamp >= VISIBLE_TIME_RANGE_NS) {
                mNumShakes++;
            }
            mLastShakeTimestamp = currentTimestamp;
            if (mNumShakes >= mMinNumShakes) {
                mNumShakes = 0;
                mLastShakeTimestamp = 0;
                mShakeListener.onShake();
            }
        }
        if (currentTimestamp - mLastShakeTimestamp > SHAKING_WINDOW_NS) {
            mNumShakes = 0;
            mLastShakeTimestamp = 0;
        }
    }
}