/*
 * Copyright (C) 2012 ZXing authors
 *
 * 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.google.zxing.client.android;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Handler;

import com.journeyapps.barcodescanner.camera.CameraManager;
import com.journeyapps.barcodescanner.camera.CameraSettings;

/**
 * Detects ambient light and switches on the front light when very dark, and off again when sufficiently light.
 *
 * @author Sean Owen
 * @author Nikolaus Huber
 */
public final class AmbientLightManager implements SensorEventListener {

    private static final float TOO_DARK_LUX = 45.0f;
    private static final float BRIGHT_ENOUGH_LUX = 450.0f;

    private CameraManager cameraManager;
    private CameraSettings cameraSettings;
    private Sensor lightSensor;
    private Context context;

    private Handler handler;

    public AmbientLightManager(Context context, CameraManager cameraManager, CameraSettings settings) {
        this.context = context;
        this.cameraManager = cameraManager;
        this.cameraSettings = settings;

        this.handler = new Handler();
    }

    public void start() {
        if (cameraSettings.isAutoTorchEnabled()) {
            SensorManager sensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
            lightSensor = sensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
            if (lightSensor != null) {
                sensorManager.registerListener(this, lightSensor, SensorManager.SENSOR_DELAY_NORMAL);
            }
        }
    }

    public void stop() {
        if (lightSensor != null) {
            SensorManager sensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
            sensorManager.unregisterListener(this);
            lightSensor = null;
        }
    }

    private void setTorch(final boolean on) {
        handler.post(() -> cameraManager.setTorch(on));
    }

    @Override
    public void onSensorChanged(SensorEvent sensorEvent) {
        float ambientLightLux = sensorEvent.values[0];
        if (cameraManager != null) {
            if (ambientLightLux <= TOO_DARK_LUX) {
                setTorch(true);
            } else if (ambientLightLux >= BRIGHT_ENOUGH_LUX) {
                setTorch(false);
            }
        }
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // do nothing
    }
}