package lu.circl.mispbump.cam;

import android.Manifest;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.content.res.Configuration;
import android.graphics.Bitmap;
import android.graphics.ImageFormat;
import android.graphics.Matrix;
import android.graphics.Point;
import android.graphics.RectF;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.renderscript.Allocation;
import android.renderscript.Element;
import android.renderscript.RenderScript;
import android.renderscript.ScriptIntrinsicYuvToRGB;
import android.renderscript.Type;
import android.util.Log;
import android.util.Size;
import android.util.SparseArray;
import android.util.SparseIntArray;
import android.view.LayoutInflater;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.fragment.app.DialogFragment;
import androidx.fragment.app.Fragment;

import com.google.android.gms.vision.Frame;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

import lu.circl.mispbump.R;

public class CameraFragment extends Fragment implements ActivityCompat.OnRequestPermissionsResultCallback {

    private class ImageProcessingThread extends Thread {

        private boolean isRunning = true;
        private int lastAccessedIndex = 0;
        private Bitmap[] processQueue = new Bitmap[10];

        ImageProcessingThread() {
            Log.i(TAG, "Image worker thread created");
        }

        void addToQueue(Bitmap bitmap) {
            processQueue[lastAccessedIndex] = bitmap;
            // circular array access
            lastAccessedIndex = (lastAccessedIndex + 1) % processQueue.length;
        }

        @Override
        public void run() {
            while (isRunning) {

                // no need to process further images
                if (!readQrEnabled) {
                    continue;
                }

                for (int i = 0; i < processQueue.length; i++) {

                    // queue position already processed or not in use
                    if (processQueue[i] == null) {
                        continue;
                    }

                    // analyze image for qr codes
                    SparseArray<Barcode> barcodes = barcodeDetector.detect(
                            new Frame.Builder().setBitmap(processQueue[i]).build()
                    );

                    // does the frame contain any qr code?
                    if (barcodes.size() > 0) {
                        if (readQrEnabled) {
                            qrResultCallback.qrScanResult(barcodes.valueAt(0).rawValue);
                        }
                    }

                    // set buffer entry as processed
                    processQueue[i] = null;
                }

                // sleep between analysis of buffer (-25% cpu usage)
                try {
                    sleep(250);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private static final String TAG = "CAMERA";

    private View hideCamView;

    private QrScanCallback qrResultCallback;

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
    }

    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
    private static final int REQUEST_CAMERA_PERMISSION = 1;
    private static final String FRAGMENT_DIALOG = "dialog";

    static {
        ORIENTATIONS.append(Surface.ROTATION_0, 90);
        ORIENTATIONS.append(Surface.ROTATION_90, 0);
        ORIENTATIONS.append(Surface.ROTATION_180, 270);
        ORIENTATIONS.append(Surface.ROTATION_270, 180);
    }

    /**
     * Max preview width that is guaranteed by Camera2 API
     */
    private static final int MAX_PREVIEW_WIDTH = 1920;

    /**
     * Max preview height that is guaranteed by Camera2 API
     */
    private static final int MAX_PREVIEW_HEIGHT = 1080;

    /**
     * {@link TextureView.SurfaceTextureListener} handles several lifecycle events on a
     * {@link TextureView}.
     */
    private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() {

        boolean processing = false;

        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {
            Log.i(TAG, "Width: " + width + "; height: " + height);
            openCamera(width, height);
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {
            configureTransform(width, height);
        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
            return true;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture texture) {
        }
    };

    private ImageProcessingThread imageProcessingThread;

    /**
     * ID of the current {@link CameraDevice}.
     */
    private String mCameraId;

    /**
     * An {@link AutoFitTextureView} for camera preview.
     */
    private AutoFitTextureView autoFitTextureView;

    /**
     * A {@link CameraCaptureSession } for camera preview.
     */
    private CameraCaptureSession previewCaptureSession;

    /**
     * A reference to the opened {@link CameraDevice}.
     */
    private CameraDevice mCameraDevice;

    /**
     * The {@link android.util.Size} of camera preview.
     */
    private Size mPreviewSize;

    /**
     * {@link CameraDevice.StateCallback} is called when {@link CameraDevice} changes its state.
     */
    private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {

        @Override
        public void onOpened(@NonNull CameraDevice cameraDevice) {
            // This method is called when the camera is opened.  We start camera preview here.
            mCameraOpenCloseLock.release();
            mCameraDevice = cameraDevice;
            createCameraPreviewSession();
        }

        @Override
        public void onDisconnected(@NonNull CameraDevice cameraDevice) {
            mCameraOpenCloseLock.release();
            cameraDevice.close();
            mCameraDevice = null;
        }

        @Override
        public void onError(@NonNull CameraDevice cameraDevice, int error) {
            mCameraOpenCloseLock.release();
            cameraDevice.close();
            mCameraDevice = null;
            Activity activity = getActivity();
            if (null != activity) {
                activity.finish();
            }
        }

    };

    /**
     * An additional thread for running tasks that shouldn't block the UI.
     */
    private HandlerThread mBackgroundThread;

    /**
     * A {@link Handler} for running tasks in the background.
     */
    private Handler mBackgroundHandler;

    /**
     * An {@link ImageReader} that handles still bitmap capture.
     */
    private ImageReader stillImageReader;

    /**
     * This a callback object for the {@link ImageReader}. "onImageAvailable" will be called when a
     * still bitmap is ready to be saved.
     */
    private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Image image = reader.acquireNextImage();
            Bitmap bitmap = YUV2Bitmap(image);
            imageProcessingThread.addToQueue(bitmap);
            image.close();
        }
    };

    /**
     * {@link CaptureRequest.Builder} for the camera preview
     */
    private CaptureRequest.Builder mPreviewRequestBuilder;

    /**
     * {@link CaptureRequest} generated by {@link #mPreviewRequestBuilder}
     */
    private CaptureRequest mPreviewRequest;

    /**
     * A {@link Semaphore} to prevent the app from exiting before closing the camera.
     */
    private Semaphore mCameraOpenCloseLock = new Semaphore(1);

    /**
     * Shows a {@link Toast} on the UI thread.
     *
     * @param text The message to show
     */
    private void showToast(final String text) {
        final Activity activity = getActivity();
        if (activity != null) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(activity, text, Toast.LENGTH_SHORT).show();
                }
            });
        }
    }

    /**
     * Given {@code choices} of {@code Size}s supported by a camera, choose the smallest one that
     * is at least as large as the respective texture view size, and that is at most as large as the
     * respective max size, and whose aspect ratio matches with the specified value. If such size
     * doesn't exist, choose the largest one that is at most as large as the respective max size,
     * and whose aspect ratio matches with the specified value.
     *
     * @param choices           The list of sizes that the camera supports for the intended output
     *                          class
     * @param textureViewWidth  The width of the texture view relative to sensor coordinate
     * @param textureViewHeight The height of the texture view relative to sensor coordinate
     * @param maxWidth          The maximum width that can be chosen
     * @param maxHeight         The maximum height that can be chosen
     * @param aspectRatio       The aspect ratio
     * @return The optimal {@code Size}, or an arbitrary one if none were big enough
     */
    private static Size chooseOptimalSize(Size[] choices, int textureViewWidth, int textureViewHeight, int maxWidth, int maxHeight, Size aspectRatio) {

        // Collect the supported resolutions that are at least as big as the preview Surface
        List<Size> bigEnough = new ArrayList<>();

        // Collect the supported resolutions that are smaller than the preview Surface
        List<Size> notBigEnough = new ArrayList<>();
        int w = aspectRatio.getWidth();
        int h = aspectRatio.getHeight();

        for (Size option : choices) {
            if (option.getWidth() <= maxWidth && option.getHeight() <= maxHeight && option.getHeight() == option.getWidth() * h / w) {
                if (option.getWidth() >= textureViewWidth && option.getHeight() >= textureViewHeight) {
                    bigEnough.add(option);
                } else {
                    notBigEnough.add(option);
                }
            }
        }

        // Pick the smallest of those big enough. If there is no one big enough, pick the
        // largest of those not big enough.
        if (bigEnough.size() > 0) {
            return Collections.min(bigEnough, new CompareSizesByArea());
        } else if (notBigEnough.size() > 0) {
            return Collections.max(notBigEnough, new CompareSizesByArea());
        } else {
            Log.e(TAG, "Couldn't find any suitable preview size");
            return choices[0];
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_camera, container, false);

        hideCamView = v.findViewById(R.id.hideCam);
        hideCamView.setVisibility(View.GONE);

        initRenderScript();
        setUpBarcodeDetector();
        return v;
    }

    @Override
    public void onViewCreated(final View view, Bundle savedInstanceState) {
        autoFitTextureView = view.findViewById(R.id.texture);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
    }

    @Override
    public void onResume() {
        super.onResume();
        enablePreview();
//        startBackgroundThread();
//
//        imageProcessingThread = new ImageProcessingThread();
//        imageProcessingThread.start();
//
//        // When the screen is turned off and turned back on, the SurfaceTexture is already
//        // available, and "onSurfaceTextureAvailable" will not be called. In that case, we can open
//        // a camera and start preview from here (otherwise, we wait until the surface is ready in
//        // the SurfaceTextureListener).
//        if (autoFitTextureView.isAvailable()) {
//            openCamera(autoFitTextureView.getWidth(), autoFitTextureView.getHeight());
//        } else {
//            autoFitTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
//        }
    }

    @Override
    public void onPause() {
        closeCamera();
        stopBackgroundThread();

        if (imageProcessingThread.isAlive()) {
            imageProcessingThread.isRunning = false;
        }

        super.onPause();
    }

    private void requestCameraPermission() {
        if (shouldShowRequestPermissionRationale(Manifest.permission.CAMERA)) {
            new ConfirmationDialog().show(getChildFragmentManager(), FRAGMENT_DIALOG);
        } else {
            requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.length != 1 || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                ErrorDialog.newInstance("REQUEST PERMISSION").show(getChildFragmentManager(), FRAGMENT_DIALOG);
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

    /**
     * Sets up member variables related to camera.
     *
     * @param width  The width of available size for camera preview
     * @param height The height of available size for camera preview
     */
    @SuppressWarnings("SuspiciousNameCombination")
    private void setUpCameraOutputs(int width, int height) {
        Activity activity = getActivity();
        assert activity != null;
        CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);

        try {
            for (String cameraId : manager.getCameraIdList()) {

                CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

                Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);

                if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
                    continue;
                }

                StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);

                if (map == null) {
                    continue;
                }

                // For still bitmap captures, we use the largest available size.
                Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.YUV_420_888)), new CompareSizesByArea());

                stillImageReader = ImageReader.newInstance(largest.getWidth() / 8, largest.getHeight() / 8, ImageFormat.YUV_420_888, 2);
                stillImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mBackgroundHandler);

                // Find out if we need to swap dimension to get the preview size relative to sensor coordinate.
                int displayRotation = activity.getWindowManager().getDefaultDisplay().getRotation();

                //noinspection ConstantConditions
                int mSensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
                boolean swappedDimensions = false;
                switch (displayRotation) {
                    case Surface.ROTATION_0:
                    case Surface.ROTATION_180:
                        if (mSensorOrientation == 90 || mSensorOrientation == 270) {
                            swappedDimensions = true;
                        }
                        break;
                    case Surface.ROTATION_90:
                    case Surface.ROTATION_270:
                        if (mSensorOrientation == 0 || mSensorOrientation == 180) {
                            swappedDimensions = true;
                        }
                        break;
                    default:
                        Log.e(TAG, "Display rotation is invalid: " + displayRotation);
                }

                Point displaySize = new Point();
                activity.getWindowManager().getDefaultDisplay().getSize(displaySize);

                int rotatedPreviewWidth = width;
                int rotatedPreviewHeight = height;
                int maxPreviewWidth = displaySize.x;
                int maxPreviewHeight = displaySize.y;

                if (swappedDimensions) {
                    rotatedPreviewWidth = height;
                    rotatedPreviewHeight = width;
                    maxPreviewWidth = displaySize.y;
                    maxPreviewHeight = displaySize.x;
                }

                if (maxPreviewWidth > MAX_PREVIEW_WIDTH) {
                    maxPreviewWidth = MAX_PREVIEW_WIDTH;
                }

                if (maxPreviewHeight > MAX_PREVIEW_HEIGHT) {
                    maxPreviewHeight = MAX_PREVIEW_HEIGHT;
                }

                Size[] sizes = map.getOutputSizes(SurfaceTexture.class);

                for (Size size : sizes) {
                    Log.i(TAG, size.toString());
                }

                // Danger, W.R.! Attempting to use too large a preview size could  exceed the camera
                // bus' bandwidth limitation, resulting in gorgeous previews but the storage of
                // garbage capture data.
                mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
                        rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,
                        maxPreviewHeight, largest);

                // We fit the aspect ratio of TextureView to the size of preview we picked.
                int orientation = getResources().getConfiguration().orientation;

                if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
                    autoFitTextureView.setAspectRatio(mPreviewSize.getWidth(), mPreviewSize.getHeight());
                } else {
                    autoFitTextureView.setAspectRatio(mPreviewSize.getHeight(), mPreviewSize.getWidth());
                }

                mCameraId = cameraId;
                return;
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            // Currently an NPE is thrown when the Camera2API is used but not supported on the
            // device this code runs.
            ErrorDialog.newInstance("CAMERA ERROR").show(getChildFragmentManager(), FRAGMENT_DIALOG);
        }
    }

    /**
     * Opens the camera specified by {@link CameraFragment#mCameraId}.
     */
    private void openCamera(int width, int height) {
        Activity activity = getActivity();

        if (ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            requestCameraPermission();
            return;
        }

        setUpCameraOutputs(width, height);
        configureTransform(width, height);

        CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);

        try {

            if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
                throw new RuntimeException("Time out waiting to lock camera opening.");
            }

            manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
        }
    }

    /**
     * Closes the current {@link CameraDevice}.
     */
    private void closeCamera() {
        try {
            mCameraOpenCloseLock.acquire();

            if (null != previewCaptureSession) {
                previewCaptureSession.close();
                previewCaptureSession = null;
            }

            if (null != mCameraDevice) {
                mCameraDevice.close();
                mCameraDevice = null;
            }

            if (null != stillImageReader) {
                stillImageReader.close();
                stillImageReader = null;
            }

        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
        } finally {
            mCameraOpenCloseLock.release();
        }
    }

    /**
     * Starts a background thread and its {@link Handler}.
     */
    private void startBackgroundThread() {
        mBackgroundThread = new HandlerThread("CameraBackground");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }

    /**
     * Stops the background thread and its {@link Handler}.
     */
    private void stopBackgroundThread() {

        if (mBackgroundThread == null) {
            return;
        }

        try {
            mBackgroundThread.quitSafely();
            mBackgroundThread.join();
            mBackgroundThread = null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    /**
     * Creates a new {@link CameraCaptureSession} for camera preview.
     */
    private void createCameraPreviewSession() {
        try {
            // from AutoFitTextureView
            SurfaceTexture texture = autoFitTextureView.getSurfaceTexture();

            // We configure the size of default buffer to be the size of camera preview we want.
            texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());

            // This is the output Surface we need to start preview.
            Surface surface = new Surface(texture);
            Surface mImageSurface = stillImageReader.getSurface();

            // We set up a CaptureRequest.Builder with the output Surface.
            mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); // TEMPLATE_ZERO_SHUTTER_LAG
            mPreviewRequestBuilder.addTarget(surface);
            mPreviewRequestBuilder.addTarget(mImageSurface);

            // Here, we create a CameraCaptureSession for camera preview.
            mCameraDevice.createCaptureSession(Arrays.asList(surface, stillImageReader.getSurface()),
                    new CameraCaptureSession.StateCallback() {

                        @Override
                        public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                            // The camera is already closed
                            if (null == mCameraDevice) {
                                return;
                            }

                            // When the session is ready, we start displaying the preview.
                            previewCaptureSession = cameraCaptureSession;
                            try {
                                // Auto focus should be continuous for camera preview.
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE); // CONTROL_AF_MODE_CONTINUOUS_PICTURE

                                // Finally, we start displaying the camera preview.
                                mPreviewRequest = mPreviewRequestBuilder.build();
                                previewCaptureSession.setRepeatingRequest(mPreviewRequest, null, mBackgroundHandler);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                            showToast("Failed");
                        }
                    }, null
            );
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    /**
     * Configures the necessary {@link android.graphics.Matrix} transformation to `autoFitTextureView`.
     * This method should be called after the camera preview size is determined in
     * setUpCameraOutputs and also the size of `autoFitTextureView` is fixed.
     *
     * @param viewWidth  The width of `autoFitTextureView`
     * @param viewHeight The height of `autoFitTextureView`
     */
    private void configureTransform(int viewWidth, int viewHeight) {
        Activity activity = getActivity();

        if (null == autoFitTextureView || null == mPreviewSize || null == activity) {
            return;
        }

        int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();

        Matrix matrix = new Matrix();
        RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
        RectF bufferRect = new RectF(0, 0, mPreviewSize.getHeight(), mPreviewSize.getWidth());
        float centerX = viewRect.centerX();
        float centerY = viewRect.centerY();

        if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {
            bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
            matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
            float scale = Math.max(
                    (float) viewHeight / mPreviewSize.getHeight(),
                    (float) viewWidth / mPreviewSize.getWidth());
            matrix.postScale(scale, scale, centerX, centerY);
            matrix.postRotate(90 * (rotation - 2), centerX, centerY);
        } else if (Surface.ROTATION_180 == rotation) {
            matrix.postRotate(180, centerX, centerY);
        }
        autoFitTextureView.setTransform(matrix);
    }

    /**
     * Compares two {@code Size}s based on their areas.
     */
    static class CompareSizesByArea implements Comparator<Size> {

        @Override
        public int compare(Size lhs, Size rhs) {
            // We cast here to ensure the multiplications won't overflow
            return Long.signum((long) lhs.getWidth() * lhs.getHeight() - (long) rhs.getWidth() * rhs.getHeight());
        }

    }

    /**
     * Shows an error message dialog.
     */
    public static class ErrorDialog extends DialogFragment {

        private static final String ARG_MESSAGE = "message";

        public static ErrorDialog newInstance(String message) {
            ErrorDialog dialog = new ErrorDialog();
            Bundle args = new Bundle();
            args.putString(ARG_MESSAGE, message);
            dialog.setArguments(args);
            return dialog;
        }

        @NonNull
        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            final Activity activity = getActivity();
            return new AlertDialog.Builder(activity)
                    .setMessage(getArguments().getString(ARG_MESSAGE))
                    .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            activity.finish();
                        }
                    })
                    .create();
        }

    }

    /**
     * Shows OK/Cancel confirmation dialog about camera permission.
     */
    public static class ConfirmationDialog extends DialogFragment {

        @NonNull
        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            final Fragment parent = getParentFragment();
            return new AlertDialog.Builder(getActivity())
                    .setMessage("REQUEST PERMISSION")
                    .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            parent.requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
                        }
                    })
                    .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            Activity activity = parent.getActivity();
                            if (activity != null) {
                                activity.finish();
                            }
                        }
                    })
                    .create();
        }
    }


    public interface QrScanCallback {
        void qrScanResult(String qrData);
    }

    public interface CameraReadyCallback {
        void ready();
    }

    private CameraReadyCallback cameraReadyCallback;
    private boolean readQrEnabled = true;
    private BarcodeDetector barcodeDetector;
    private RenderScript renderScript;

    private void initRenderScript() {
        renderScript = RenderScript.create(getActivity());
    }

    private Bitmap YUV2Bitmap(Image image) {

        if (image == null) {
            return null;
        }

        ScriptIntrinsicYuvToRGB yuvToRgbIntrinsic = ScriptIntrinsicYuvToRGB.create(renderScript, Element.U8_4(renderScript));

        int W = image.getWidth();
        int H = image.getHeight();

        Image.Plane Y = image.getPlanes()[0];
        Image.Plane U = image.getPlanes()[1];
        Image.Plane V = image.getPlanes()[2];

        int Yb = Y.getBuffer().remaining();
        int Ub = U.getBuffer().remaining();
        int Vb = V.getBuffer().remaining();

        byte[] data = new byte[Yb + Ub + Vb];

        Y.getBuffer().get(data, 0, Yb);
        V.getBuffer().get(data, Yb, Vb);
        U.getBuffer().get(data, Yb + Vb, Ub);

        Type.Builder yuvType = new Type.Builder(renderScript, Element.U8(renderScript)).setX(data.length);
        Allocation in = Allocation.createTyped(renderScript, yuvType.create(), Allocation.USAGE_SCRIPT);

        Type.Builder rgbaType = new Type.Builder(renderScript, Element.RGBA_8888(renderScript)).setX(W).setY(H);
        Allocation out = Allocation.createTyped(renderScript, rgbaType.create(), Allocation.USAGE_SCRIPT);

        final Bitmap bmpout = Bitmap.createBitmap(W, H, Bitmap.Config.ARGB_8888);

        in.copyFromUnchecked(data);

        yuvToRgbIntrinsic.setInput(in);
        yuvToRgbIntrinsic.forEach(out);

        out.copyTo(bmpout);
        image.close();

        return bmpout;
    }

    public void setReadQrEnabled(boolean enabled) {
        readQrEnabled = enabled;
    }

    public void disablePreview() {
        hideCamView.setAlpha(0f);
        hideCamView.setVisibility(View.VISIBLE);
        hideCamView.animate()
                .alpha(1f)
                .setDuration(250)
                .setListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        closeCamera();
                        stopBackgroundThread();

                        if (imageProcessingThread.isAlive()) {
                            imageProcessingThread.isRunning = false;
                        }
                    }
                });
    }

    public void enablePreview() {

        startBackgroundThread();

        imageProcessingThread = new ImageProcessingThread();
        imageProcessingThread.start();

        if (autoFitTextureView.isAvailable()) {
            openCamera(autoFitTextureView.getWidth(), autoFitTextureView.getHeight());
        } else {
            autoFitTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
        }

        hideCamView.setAlpha(1f);
        hideCamView.setVisibility(View.VISIBLE);
        hideCamView.animate()
                .alpha(0f)
                .setStartDelay(100)
                .setDuration(1000)
                .setListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        hideCamView.setVisibility(View.GONE);
                        if (cameraReadyCallback != null) {
                            cameraReadyCallback.ready();
                        }
                    }
                });
    }

    private void setUpBarcodeDetector() {
        barcodeDetector = new BarcodeDetector.Builder(getActivity())
                .setBarcodeFormats(Barcode.QR_CODE)
                .build();

        if (!barcodeDetector.isOperational()) {
            Toast.makeText(getActivity(), "Could not setup QR-Code scanner!", Toast.LENGTH_SHORT).show();
        }
    }

    public void setOnQrAvailableListener(QrScanCallback callback) {
        qrResultCallback = callback;
    }

    public void setCameraReadyCallback(CameraReadyCallback callback) {
        this.cameraReadyCallback = callback;
    }
}