/*
 * Copyright 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.example.android.camera2raw;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.app.Fragment;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.ImageFormat;
import android.graphics.Matrix;
import android.graphics.RectF;
import android.graphics.SurfaceTexture;
import android.hardware.SensorManager;
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.CameraMetadata;
import android.hardware.camera2.CaptureFailure;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.CaptureResult;
import android.hardware.camera2.DngCreator;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.media.MediaScannerConnection;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.os.SystemClock;
import android.util.Log;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.LayoutInflater;
import android.view.OrientationEventListener;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A fragment that demonstrates use of the Camera2 API to capture RAW and JPEG photos.
 *
 * In this example, the lifecycle of a single request to take a photo is:
 * <ul>
 * <li>
 * The user presses the "Picture" button, resulting in a call to {@link #takePicture()}.
 * </li>
 * <li>
 * {@link #takePicture()} initiates a pre-capture sequence that triggers the camera's built-in
 * auto-focus, auto-exposure, and auto-white-balance algorithms (aka. "3A") to run.
 * </li>
 * <li>
 * When the pre-capture sequence has finished, a {@link CaptureRequest} with a monotonically
 * increasing request ID set by calls to {@link CaptureRequest.Builder#setTag(Object)} is sent to
 * the camera to begin the JPEG and RAW capture sequence, and an
 * {@link ImageSaver.ImageSaverBuilder} is stored for this request in the
 * {@link #mJpegResultQueue} and {@link #mRawResultQueue}.
 * </li>
 * <li>
 * As {@link CaptureResult}s and {@link Image}s become available via callbacks in a background
 * thread, a {@link ImageSaver.ImageSaverBuilder} is looked up by the request ID in
 * {@link #mJpegResultQueue} and {@link #mRawResultQueue} and updated.
 * </li>
 * <li>
 * When all of the necessary results to save an image are available, the an {@link ImageSaver} is
 * constructed by the {@link ImageSaver.ImageSaverBuilder} and passed to a separate background
 * thread to save to a file.
 * </li>
 * </ul>
 */
public class Camera2RawFragment extends Fragment implements View.OnClickListener {
    /**
     * Conversion from screen rotation to JPEG orientation.
     */
    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();

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

    /**
     * Timeout for the pre-capture sequence.
     */
    private static final long PRECAPTURE_TIMEOUT_MS = 1000;

    /**
     * Tolerance when comparing aspect ratios.
     */
    private static final double ASPECT_RATIO_TOLERANCE = 0.005;

    /**
     * Tag for the {@link Log}.
     */
    private static final String TAG = "Camera2RawFragment";

    /**
     * Camera state: Device is closed.
     */
    private static final int STATE_CLOSED = 0;

    /**
     * Camera state: Device is opened, but is not capturing.
     */
    private static final int STATE_OPENED = 1;

    /**
     * Camera state: Showing camera preview.
     */
    private static final int STATE_PREVIEW = 2;

    /**
     * Camera state: Waiting for 3A convergence before capturing a photo.
     */
    private static final int STATE_WAITING_FOR_3A_CONVERGENCE = 3;

    /**
     * An {@link OrientationEventListener} used to determine when device rotation has occurred.
     * This is mainly necessary for when the device is rotated by 180 degrees, in which case
     * onCreate or onConfigurationChanged is not called as the view dimensions remain the same,
     * but the orientation of the has changed, and thus the preview rotation must be updated.
     */
    private OrientationEventListener mOrientationListener;

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

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

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

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
            synchronized (mCameraStateLock) {
                mPreviewSize = null;
            }
            return true;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture texture) {
        }

    };

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

    /**
     * An additional thread for running tasks that shouldn't block the UI.  This is used for all
     * callbacks from the {@link CameraDevice} and {@link CameraCaptureSession}s.
     */
    private HandlerThread mBackgroundThread;

    /**
     * A counter for tracking corresponding {@link CaptureRequest}s and {@link CaptureResult}s
     * across the {@link CameraCaptureSession} capture callbacks.
     */
    private final AtomicInteger mRequestCounter = new AtomicInteger();

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

    /**
     * A lock protecting camera state.
     */
    private final Object mCameraStateLock = new Object();

    // *********************************************************************************************
    // State protected by mCameraStateLock.
    //
    // The following state is used across both the UI and background threads.  Methods with "Locked"
    // in the name expect mCameraStateLock to be held while calling.

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

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

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

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

    /**
     * The {@link CameraCharacteristics} for the currently configured camera device.
     */
    private CameraCharacteristics mCharacteristics;

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

    /**
     * A reference counted holder wrapping the {@link ImageReader} that handles JPEG image captures.
     * This is used to allow us to clean up the {@link ImageReader} when all background tasks using
     * its {@link Image}s have completed.
     */
    private RefCountedAutoCloseable<ImageReader> mJpegImageReader;

    /**
     * A reference counted holder wrapping the {@link ImageReader} that handles RAW image captures.
     * This is used to allow us to clean up the {@link ImageReader} when all background tasks using
     * its {@link Image}s have completed.
     */
    private RefCountedAutoCloseable<ImageReader> mRawImageReader;

    /**
     * Whether or not the currently configured camera device is fixed-focus.
     */
    private boolean mNoAFRun = false;

    /**
     * Number of pending user requests to capture a photo.
     */
    private int mPendingUserCaptures = 0;

    /**
     * Request ID to {@link ImageSaver.ImageSaverBuilder} mapping for in-progress JPEG captures.
     */
    private final TreeMap<Integer, ImageSaver.ImageSaverBuilder> mJpegResultQueue = new TreeMap<>();

    /**
     * Request ID to {@link ImageSaver.ImageSaverBuilder} mapping for in-progress RAW captures.
     */
    private final TreeMap<Integer, ImageSaver.ImageSaverBuilder> mRawResultQueue = new TreeMap<>();

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

    /**
     * The state of the camera device.
     *
     * @see #mPreCaptureCallback
     */
    private int mState = STATE_CLOSED;

    /**
     * Timer to use with pre-capture sequence to ensure a timely capture if 3A convergence is taking
     * too long.
     */
    private long mCaptureTimer;

    //**********************************************************************************************

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

        @Override
        public void onOpened(CameraDevice cameraDevice) {
            // This method is called when the camera is opened.  We start camera preview here if
            // the TextureView displaying this has been set up.
            synchronized (mCameraStateLock) {
                mState = STATE_OPENED;
                mCameraOpenCloseLock.release();
                mCameraDevice = cameraDevice;

                // Start the preview session if the TextureView has been set up already.
                if (mPreviewSize != null && mTextureView.isAvailable()) {
                    createCameraPreviewSessionLocked();
                }
            }
        }

        @Override
        public void onDisconnected(CameraDevice cameraDevice) {
            synchronized (mCameraStateLock) {
                mState = STATE_CLOSED;
                mCameraOpenCloseLock.release();
                cameraDevice.close();
                mCameraDevice = null;
            }
        }

        @Override
        public void onError(CameraDevice cameraDevice, int error) {
            Log.e(TAG, "Received camera device error: " + error);
            synchronized(mCameraStateLock) {
                mState = STATE_CLOSED;
                mCameraOpenCloseLock.release();
                cameraDevice.close();
                mCameraDevice = null;
            }
            Activity activity = getActivity();
            if (null != activity) {
                activity.finish();
            }
        }

    };

    /**
     * This a callback object for the {@link ImageReader}. "onImageAvailable" will be called when a
     * JPEG image is ready to be saved.
     */
    private final ImageReader.OnImageAvailableListener mOnJpegImageAvailableListener
            = new ImageReader.OnImageAvailableListener() {

        @Override
        public void onImageAvailable(ImageReader reader) {
            dequeueAndSaveImage(mJpegResultQueue, mJpegImageReader);
        }

    };

    /**
     * This a callback object for the {@link ImageReader}. "onImageAvailable" will be called when a
     * RAW image is ready to be saved.
     */
    private final ImageReader.OnImageAvailableListener mOnRawImageAvailableListener
            = new ImageReader.OnImageAvailableListener() {

        @Override
        public void onImageAvailable(ImageReader reader) {
            dequeueAndSaveImage(mRawResultQueue, mRawImageReader);
        }

    };

    /**
     * A {@link CameraCaptureSession.CaptureCallback} that handles events for the preview and
     * pre-capture sequence.
     */
    private CameraCaptureSession.CaptureCallback mPreCaptureCallback
            = new CameraCaptureSession.CaptureCallback() {

        private void process(CaptureResult result) {
            synchronized(mCameraStateLock) {
                switch (mState) {
                    case STATE_PREVIEW: {
                        // We have nothing to do when the camera preview is running normally.
                        break;
                    }
                    case STATE_WAITING_FOR_3A_CONVERGENCE: {
                        boolean readyToCapture = true;
                        if (!mNoAFRun) {
                            int afState = result.get(CaptureResult.CONTROL_AF_STATE);

                            // If auto-focus has reached locked state, we are ready to capture
                            readyToCapture =
                                    (afState == CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED ||
                                    afState == CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED);
                        }

                        // If we are running on an non-legacy device, we should also wait until
                        // auto-exposure and auto-white-balance have converged as well before
                        // taking a picture.
                        if (!isLegacyLocked()) {
                            int aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                            int awbState = result.get(CaptureResult.CONTROL_AWB_STATE);

                            readyToCapture = readyToCapture &&
                                    aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED &&
                                    awbState == CaptureResult.CONTROL_AWB_STATE_CONVERGED;
                        }

                        // If we haven't finished the pre-capture sequence but have hit our maximum
                        // wait timeout, too bad! Begin capture anyway.
                        if (!readyToCapture && hitTimeoutLocked()) {
                            Log.w(TAG, "Timed out waiting for pre-capture sequence to complete.");
                            readyToCapture = true;
                        }

                        if (readyToCapture && mPendingUserCaptures > 0) {
                            // Capture once for each user tap of the "Picture" button.
                            while (mPendingUserCaptures > 0) {
                                captureStillPictureLocked();
                                mPendingUserCaptures--;
                            }
                            // After this, the camera will go back to the normal state of preview.
                            mState = STATE_PREVIEW;
                        }
                    }
                }
            }
        }

        @Override
        public void onCaptureProgressed(CameraCaptureSession session, CaptureRequest request,
                                        CaptureResult partialResult) {
            process(partialResult);
        }

        @Override
        public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request,
                                       TotalCaptureResult result) {
            process(result);
        }

    };

    /**
     * A {@link CameraCaptureSession.CaptureCallback} that handles the still JPEG and RAW capture
     * request.
     */
    private final CameraCaptureSession.CaptureCallback mCaptureCallback
            = new CameraCaptureSession.CaptureCallback() {
        @Override
        public void onCaptureStarted(CameraCaptureSession session, CaptureRequest request,
                                     long timestamp, long frameNumber) {
            String currentDateTime = generateTimestamp();
            File rawFile = new File(Environment.
                    getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM),
                    "RAW_" + currentDateTime + ".dng");
            File jpegFile = new File(Environment.
                    getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM),
                    "JPEG_" + currentDateTime + ".jpg");

            // Look up the ImageSaverBuilder for this request and update it with the file name
            // based on the capture start time.
            ImageSaver.ImageSaverBuilder jpegBuilder;
            ImageSaver.ImageSaverBuilder rawBuilder;
            int requestId = (int) request.getTag();
            synchronized (mCameraStateLock) {
                jpegBuilder = mJpegResultQueue.get(requestId);
                rawBuilder = mRawResultQueue.get(requestId);
            }

            if (jpegBuilder != null) jpegBuilder.setFile(jpegFile);
            if (rawBuilder != null) rawBuilder.setFile(rawFile);
        }

        @Override
        public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request,
                                       TotalCaptureResult result) {
            int requestId = (int) request.getTag();
            ImageSaver.ImageSaverBuilder jpegBuilder;
            ImageSaver.ImageSaverBuilder rawBuilder;
            StringBuilder sb = new StringBuilder();

            // Look up the ImageSaverBuilder for this request and update it with the CaptureResult
            synchronized (mCameraStateLock) {
                jpegBuilder = mJpegResultQueue.get(requestId);
                rawBuilder = mRawResultQueue.get(requestId);

                // If we have all the results necessary, save the image to a file in the background.
                handleCompletionLocked(requestId, jpegBuilder, mJpegResultQueue);
                handleCompletionLocked(requestId, rawBuilder, mRawResultQueue);

                if (jpegBuilder != null) {
                    jpegBuilder.setResult(result);
                    sb.append("Saving JPEG as: ");
                    sb.append(jpegBuilder.getSaveLocation());
                }
                if (rawBuilder != null) {
                    rawBuilder.setResult(result);
                    if (jpegBuilder != null) sb.append(", ");
                    sb.append("Saving RAW as: ");
                    sb.append(rawBuilder.getSaveLocation());
                }
                finishedCaptureLocked();
            }

            showToast(sb.toString());
        }

        @Override
        public void onCaptureFailed(CameraCaptureSession session, CaptureRequest request,
                                    CaptureFailure failure) {
            int requestId = (int) request.getTag();
            synchronized (mCameraStateLock) {
                mJpegResultQueue.remove(requestId);
                mRawResultQueue.remove(requestId);
                finishedCaptureLocked();
            }
            showToast("Capture failed!");
        }

    };

    /**
     * A {@link Handler} for showing {@link Toast}s on the UI thread.
     */
    private final Handler mMessageHandler = new Handler(Looper.getMainLooper()) {
        @Override
        public void handleMessage(Message msg) {
            Activity activity = getActivity();
            if (activity != null) {
                Toast.makeText(activity, (String) msg.obj, Toast.LENGTH_SHORT).show();
            }
        }
    };

    public static Camera2RawFragment newInstance() {
        Camera2RawFragment fragment = new Camera2RawFragment();
        fragment.setRetainInstance(true);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_camera2_basic, container, false);
    }

    @Override
    public void onViewCreated(final View view, Bundle savedInstanceState) {
        view.findViewById(R.id.picture).setOnClickListener(this);
        view.findViewById(R.id.info).setOnClickListener(this);
        mTextureView = (AutoFitTextureView) view.findViewById(R.id.texture);

        // Setup a new OrientationEventListener.  This is used to handle rotation events like a
        // 180 degree rotation that do not normally trigger a call to onCreate to do view re-layout
        // or otherwise cause the preview TextureView's size to change.
        mOrientationListener = new OrientationEventListener(getActivity(),
                SensorManager.SENSOR_DELAY_NORMAL) {
            @Override
            public void onOrientationChanged(int orientation) {
                if (mTextureView != null && mTextureView.isAvailable()) {
                    configureTransform(mTextureView.getWidth(), mTextureView.getHeight());
                }
            }
        };
    }

    @Override
    public void onResume() {
        super.onResume();
        startBackgroundThread();
        openCamera();

        // 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 should
        // configure the preview bounds here (otherwise, we wait until the surface is ready in
        // the SurfaceTextureListener).
        if (mTextureView.isAvailable()) {
            configureTransform(mTextureView.getWidth(), mTextureView.getHeight());
        } else {
            mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
        }
        if (mOrientationListener != null && mOrientationListener.canDetectOrientation()) {
            mOrientationListener.enable();
        }
    }

    @Override
    public void onPause() {
        if (mOrientationListener != null) {
            mOrientationListener.disable();
        }
        closeCamera();
        stopBackgroundThread();
        super.onPause();
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.picture: {
                takePicture();
                break;
            }
            case R.id.info: {
                Activity activity = getActivity();
                if (null != activity) {
                    new AlertDialog.Builder(activity)
                            .setMessage(R.string.intro_message)
                            .setPositiveButton(android.R.string.ok, null)
                            .show();
                }
                break;
            }
        }
    }

    /**
     * Sets up state related to camera that is needed before opening a {@link CameraDevice}.
     */
    private boolean setUpCameraOutputs() {
        Activity activity = getActivity();
        CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
        if (manager == null) {
            ErrorDialog.buildErrorDialog("This device doesn't support Camera2 API.").
                    show(getFragmentManager(), "dialog");
            return false;
        }
        try {
            // Find a CameraDevice that supports RAW captures, and configure state.
            for (String cameraId : manager.getCameraIdList()) {
                CameraCharacteristics characteristics
                        = manager.getCameraCharacteristics(cameraId);

                // We only use a camera that supports RAW in this sample.
                if (!contains(characteristics.get(
                        CameraCharacteristics.REQUEST_AVAILABLE_CAPABILITIES),
                        CameraCharacteristics.REQUEST_AVAILABLE_CAPABILITIES_RAW)) {
                    continue;
                }

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

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

                Size largestRaw = Collections.max(
                        Arrays.asList(map.getOutputSizes(ImageFormat.RAW_SENSOR)),
                        new CompareSizesByArea());

                synchronized(mCameraStateLock) {
                    // Set up ImageReaders for JPEG and RAW outputs.  Place these in a reference
                    // counted wrapper to ensure they are only closed when all background tasks
                    // using them are finished.
                    if (mJpegImageReader == null || mJpegImageReader.getAndRetain() == null) {
                        mJpegImageReader = new RefCountedAutoCloseable<>(
                                ImageReader.newInstance(largestJpeg.getWidth(),
                                largestJpeg.getHeight(), ImageFormat.JPEG, /*maxImages*/5));
                    }
                    mJpegImageReader.get().setOnImageAvailableListener(
                            mOnJpegImageAvailableListener, mBackgroundHandler);

                    if (mRawImageReader == null || mRawImageReader.getAndRetain() == null) {
                        mRawImageReader = new RefCountedAutoCloseable<>(
                                ImageReader.newInstance(largestRaw.getWidth(),
                                largestRaw.getHeight(), ImageFormat.RAW_SENSOR, /*maxImages*/ 5));
                    }
                    mRawImageReader.get().setOnImageAvailableListener(
                            mOnRawImageAvailableListener, mBackgroundHandler);

                    mCharacteristics = characteristics;
                    mCameraId = cameraId;
                }
                return true;
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

        // If we found no suitable cameras for capturing RAW, warn the user.
        ErrorDialog.buildErrorDialog("This device doesn't support capturing RAW photos").
                show(getFragmentManager(), "dialog");
        return false;
    }

    /**
     * Opens the camera specified by {@link #mCameraId}.
     */
    private void openCamera() {
        if (!setUpCameraOutputs()) {
            return;
        }

        Activity activity = getActivity();
        CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
        try {
            // Wait for any previously running session to finish.
            if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
                throw new RuntimeException("Time out waiting to lock camera opening.");
            }

            String cameraId;
            Handler backgroundHandler;
            synchronized (mCameraStateLock) {
                cameraId = mCameraId;
                backgroundHandler = mBackgroundHandler;
            }

            // Attempt to open the camera. mStateCallback will be called on the background handler's
            // thread when this succeeds or fails.
            manager.openCamera(cameraId, mStateCallback, backgroundHandler);
        } 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();
            synchronized(mCameraStateLock) {

                // Reset state and clean up resources used by the camera.
                // Note: After calling this, the ImageReaders will be closed after any background
                // tasks saving Images from these readers have been completed.
                mPendingUserCaptures = 0;
                mState = STATE_CLOSED;
                if (null != mCaptureSession) {
                    mCaptureSession.close();
                    mCaptureSession = null;
                }
                if (null != mCameraDevice) {
                    mCameraDevice.close();
                    mCameraDevice = null;
                }
                if (null != mJpegImageReader) {
                    mJpegImageReader.close();
                    mJpegImageReader = null;
                }
                if (null != mRawImageReader) {
                    mRawImageReader.close();
                    mRawImageReader = 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();
        synchronized(mCameraStateLock) {
            mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
        }
    }

    /**
     * Stops the background thread and its {@link Handler}.
     */
    private void stopBackgroundThread() {
        mBackgroundThread.quitSafely();
        try {
            mBackgroundThread.join();
            mBackgroundThread = null;
            synchronized (mCameraStateLock) {
                mBackgroundHandler = null;
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    /**
     * Creates a new {@link CameraCaptureSession} for camera preview.
     *
     * Call this only with {@link #mCameraStateLock} held.
     */
    private void createCameraPreviewSessionLocked() {
        try {
            SurfaceTexture texture = mTextureView.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);

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

            // Here, we create a CameraCaptureSession for camera preview.
            mCameraDevice.createCaptureSession(Arrays.asList(surface,
                    mJpegImageReader.get().getSurface(),
                    mRawImageReader.get().getSurface()), new CameraCaptureSession.StateCallback() {
                        @Override
                        public void onConfigured(CameraCaptureSession cameraCaptureSession) {
                            synchronized (mCameraStateLock) {
                                // The camera is already closed
                                if (null == mCameraDevice) {
                                    return;
                                }

                                try {
                                    setup3AControlsLocked(mPreviewRequestBuilder);
                                    // Finally, we start displaying the camera preview.
                                    cameraCaptureSession.setRepeatingRequest(
                                            mPreviewRequestBuilder.build(),
                                            mPreCaptureCallback, mBackgroundHandler);
                                    mState = STATE_PREVIEW;
                                } catch (CameraAccessException|IllegalStateException e) {
                                    e.printStackTrace();
                                    return;
                                }
                                // When the session is ready, we start displaying the preview.
                                mCaptureSession = cameraCaptureSession;
                            }
                        }

                        @Override
                        public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                            showToast("Failed to configure camera.");
                        }
                    }, mBackgroundHandler
            );
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    /**
     * Configure the given {@link CaptureRequest.Builder} to use auto-focus, auto-exposure, and
     * auto-white-balance controls if available.
     *
     * Call this only with {@link #mCameraStateLock} held.
     *
     * @param builder the builder to configure.
     */
    private void setup3AControlsLocked(CaptureRequest.Builder builder) {
        // Enable auto-magical 3A run by camera device
        builder.set(CaptureRequest.CONTROL_MODE,
                CaptureRequest.CONTROL_MODE_AUTO);

        Float minFocusDist =
                mCharacteristics.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);

        // If MINIMUM_FOCUS_DISTANCE is 0, lens is fixed-focus and we need to skip the AF run.
        mNoAFRun = (minFocusDist == null || minFocusDist == 0);

        if (!mNoAFRun) {
            // If there is a "continuous picture" mode available, use it, otherwise default to AUTO.
            if (contains(mCharacteristics.get(
                            CameraCharacteristics.CONTROL_AF_AVAILABLE_MODES),
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE)) {
                builder.set(CaptureRequest.CONTROL_AF_MODE,
                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            } else {
                builder.set(CaptureRequest.CONTROL_AF_MODE,
                        CaptureRequest.CONTROL_AF_MODE_AUTO);
            }
        }

        // If there is an auto-magical flash control mode available, use it, otherwise default to
        // the "on" mode, which is guaranteed to always be available.
        if (contains(mCharacteristics.get(
                        CameraCharacteristics.CONTROL_AE_AVAILABLE_MODES),
                CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH)) {
            builder.set(CaptureRequest.CONTROL_AE_MODE,
                    CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        } else {
            builder.set(CaptureRequest.CONTROL_AE_MODE,
                    CaptureRequest.CONTROL_AE_MODE_ON);
        }

        // If there is an auto-magical white balance control mode available, use it.
        if (contains(mCharacteristics.get(
                        CameraCharacteristics.CONTROL_AWB_AVAILABLE_MODES),
                CaptureRequest.CONTROL_AWB_MODE_AUTO)) {
            // Allow AWB to run auto-magically if this device supports this
            builder.set(CaptureRequest.CONTROL_AWB_MODE,
                    CaptureRequest.CONTROL_AWB_MODE_AUTO);
        }
    }

    /**
     * Configure the necessary {@link android.graphics.Matrix} transformation to `mTextureView`,
     * and start/restart the preview capture session if necessary.
     *
     * This method should be called after the camera state has been initialized in
     * setUpCameraOutputs.
     *
     * @param viewWidth  The width of `mTextureView`
     * @param viewHeight The height of `mTextureView`
     */
    private void configureTransform(int viewWidth, int viewHeight) {
        Activity activity = getActivity();
        synchronized(mCameraStateLock) {
            if (null == mTextureView || null == activity) {
                return;
            }

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

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

            // Find the rotation of the device relative to the native device orientation.
            int deviceRotation = activity.getWindowManager().getDefaultDisplay().getRotation();

            // Find the rotation of the device relative to the camera sensor's orientation.
            int totalRotation = sensorToDeviceRotation(mCharacteristics, deviceRotation);

            // Swap the view dimensions for calculation as needed if they are rotated relative to
            // the sensor.
            boolean swappedDimensions = totalRotation == 90 || totalRotation == 270;
            int rotatedViewWidth = viewWidth;
            int rotatedViewHeight = viewHeight;
            if (swappedDimensions) {
                rotatedViewWidth = viewHeight;
                rotatedViewHeight = viewWidth;
            }

            // Find the best preview size for these view dimensions and configured JPEG size.
            Size previewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
                    rotatedViewWidth, rotatedViewHeight, largestJpeg);

            if (swappedDimensions) {
                mTextureView.setAspectRatio(
                        previewSize.getHeight(), previewSize.getWidth());
            } else {
                mTextureView.setAspectRatio(
                        previewSize.getWidth(), previewSize.getHeight());
            }

            // Find rotation of device in degrees (reverse device orientation for front-facing
            // cameras).
            int rotation = (mCharacteristics.get(CameraCharacteristics.LENS_FACING) ==
                    CameraCharacteristics.LENS_FACING_FRONT) ?
                    (360 + ORIENTATIONS.get(deviceRotation)) % 360 :
                    (360 - ORIENTATIONS.get(deviceRotation)) % 360;

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

            // Initially, output stream images from the Camera2 API will be rotated to the native
            // device orientation from the sensor's orientation, and the TextureView will default to
            // scaling these buffers to fill it's view bounds.  If the aspect ratios and relative
            // orientations are correct, this is fine.
            //
            // However, if the device orientation has been rotated relative to its native
            // orientation so that the TextureView's dimensions are swapped relative to the
            // native device orientation, we must do the following to ensure the output stream
            // images are not incorrectly scaled by the TextureView:
            //   - Undo the scale-to-fill from the output buffer's dimensions (i.e. its dimensions
            //     in the native device orientation) to the TextureView's dimension.
            //   - Apply a scale-to-fill from the output buffer's rotated dimensions
            //     (i.e. its dimensions in the current device orientation) to the TextureView's
            //     dimensions.
            //   - Apply the rotation from the native device orientation to the current device
            //     rotation.
            if (Surface.ROTATION_90 == deviceRotation || Surface.ROTATION_270 == deviceRotation) {
                bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
                matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
                float scale = Math.max(
                        (float) viewHeight / previewSize.getHeight(),
                        (float) viewWidth / previewSize.getWidth());
                matrix.postScale(scale, scale, centerX, centerY);

            }
            matrix.postRotate(rotation, centerX, centerY);

            mTextureView.setTransform(matrix);

            // Start or restart the active capture session if the preview was initialized or
            // if its aspect ratio changed significantly.
            if (mPreviewSize == null || !checkAspectsEqual(previewSize, mPreviewSize)) {
                mPreviewSize = previewSize;
                if (mState != STATE_CLOSED) {
                    createCameraPreviewSessionLocked();
                }
            }
        }
    }

    /**
     * Initiate a still image capture.
     *
     * This function sends a capture request that initiates a pre-capture sequence in our state
     * machine that waits for auto-focus to finish, ending in a "locked" state where the lens is no
     * longer moving, waits for auto-exposure to choose a good exposure value, and waits for
     * auto-white-balance to converge.
     */
    private void takePicture() {
        synchronized(mCameraStateLock) {
            mPendingUserCaptures++;

            // If we already triggered a pre-capture sequence, or are in a state where we cannot
            // do this, return immediately.
            if (mState != STATE_PREVIEW) {
                return;
            }

            try {
                // Trigger an auto-focus run if camera is capable. If the camera is already focused,
                // this should do nothing.
                if (!mNoAFRun) {
                    mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                            CameraMetadata.CONTROL_AF_TRIGGER_START);
                }

                // If this is not a legacy device, we can also trigger an auto-exposure metering
                // run.
                if (!isLegacyLocked()) {
                    // Tell the camera to lock focus.
                    mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,
                            CameraMetadata.CONTROL_AE_PRECAPTURE_TRIGGER_START);
                }

                // Update state machine to wait for auto-focus, auto-exposure, and
                // auto-white-balance (aka. "3A") to converge.
                mState = STATE_WAITING_FOR_3A_CONVERGENCE;

                // Start a timer for the pre-capture sequence.
                startTimerLocked();

                // Replace the existing repeating request with one with updated 3A triggers.
                mCaptureSession.capture(mPreviewRequestBuilder.build(), mPreCaptureCallback,
                        mBackgroundHandler);
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Send a capture request to the camera device that initiates a capture targeting the JPEG and
     * RAW outputs.
     *
     * Call this only with {@link #mCameraStateLock} held.
     */
    private void captureStillPictureLocked() {
        try {
            final Activity activity = getActivity();
            if (null == activity || null == mCameraDevice) {
                return;
            }
            // This is the CaptureRequest.Builder that we use to take a picture.
            final CaptureRequest.Builder captureBuilder =
                    mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);

            captureBuilder.addTarget(mJpegImageReader.get().getSurface());
            captureBuilder.addTarget(mRawImageReader.get().getSurface());

            // Use the same AE and AF modes as the preview.
            setup3AControlsLocked(captureBuilder);

            // Set orientation.
            int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION,
                    sensorToDeviceRotation(mCharacteristics, rotation));

            // Set request tag to easily track results in callbacks.
            captureBuilder.setTag(mRequestCounter.getAndIncrement());

            CaptureRequest request = captureBuilder.build();

            // Create an ImageSaverBuilder in which to collect results, and add it to the queue
            // of active requests.
            ImageSaver.ImageSaverBuilder jpegBuilder = new ImageSaver.ImageSaverBuilder(activity)
                    .setCharacteristics(mCharacteristics);
            ImageSaver.ImageSaverBuilder rawBuilder = new ImageSaver.ImageSaverBuilder(activity)
                    .setCharacteristics(mCharacteristics);

            mJpegResultQueue.put((int) request.getTag(), jpegBuilder);
            mRawResultQueue.put((int) request.getTag(), rawBuilder);

            mCaptureSession.capture(request, mCaptureCallback, mBackgroundHandler);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    /**
     * Called after a RAW/JPEG capture has completed; resets the AF trigger state for the
     * pre-capture sequence.
     *
     * Call this only with {@link #mCameraStateLock} held.
     */
    private void finishedCaptureLocked() {
        try {
            // Reset the auto-focus trigger in case AF didn't run quickly enough.
            if (!mNoAFRun) {
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                        CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);

                mCaptureSession.capture(mPreviewRequestBuilder.build(), mPreCaptureCallback,
                        mBackgroundHandler);

                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                        CameraMetadata.CONTROL_AF_TRIGGER_IDLE);
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    /**
     * Retrieve the next {@link Image} from a reference counted {@link ImageReader}, retaining
     * that {@link ImageReader} until that {@link Image} is no longer in use, and set this
     * {@link Image} as the result for the next request in the queue of pending requests.  If
     * all necessary information is available, begin saving the image to a file in a background
     * thread.
     *
     * @param pendingQueue the currently active requests.
     * @param reader a reference counted wrapper containing an {@link ImageReader} from which to
     *               acquire an image.
     */
    private void dequeueAndSaveImage(TreeMap<Integer, ImageSaver.ImageSaverBuilder> pendingQueue,
                                     RefCountedAutoCloseable<ImageReader> reader) {
        synchronized (mCameraStateLock) {
            Map.Entry<Integer, ImageSaver.ImageSaverBuilder> entry =
                    pendingQueue.firstEntry();
            ImageSaver.ImageSaverBuilder builder = entry.getValue();

            // Increment reference count to prevent ImageReader from being closed while we
            // are saving its Images in a background thread (otherwise their resources may
            // be freed while we are writing to a file).
            if (reader == null || reader.getAndRetain() == null) {
                Log.e(TAG, "Paused the activity before we could save the image," +
                        " ImageReader already closed.");
                pendingQueue.remove(entry.getKey());
                return;
            }

            Image image;
            try {
                image = reader.get().acquireNextImage();
            } catch (IllegalStateException e) {
                Log.e(TAG, "Too many images queued for saving, dropping image for request: " +
                        entry.getKey());
                pendingQueue.remove(entry.getKey());
                return;
            }

            builder.setRefCountedReader(reader).setImage(image);

            handleCompletionLocked(entry.getKey(), builder, pendingQueue);
        }
    }

    /**
     * Runnable that saves an {@link Image} into the specified {@link File}, and updates
     * {@link android.provider.MediaStore} to include the resulting file.
     *
     * This can be constructed through an {@link ImageSaverBuilder} as the necessary image and
     * result information becomes available.
     */
    private static class ImageSaver implements Runnable {

        /**
         * The image to save.
         */
        private final Image mImage;
        /**
         * The file we save the image into.
         */
        private final File mFile;

        /**
         * The CaptureResult for this image capture.
         */
        private final CaptureResult mCaptureResult;

        /**
         * The CameraCharacteristics for this camera device.
         */
        private final CameraCharacteristics mCharacteristics;

        /**
         * The Context to use when updating MediaStore with the saved images.
         */
        private final Context mContext;

        /**
         * A reference counted wrapper for the ImageReader that owns the given image.
         */
        private final RefCountedAutoCloseable<ImageReader> mReader;

        private ImageSaver(Image image, File file, CaptureResult result,
                CameraCharacteristics characteristics, Context context,
                RefCountedAutoCloseable<ImageReader> reader) {
            mImage = image;
            mFile = file;
            mCaptureResult = result;
            mCharacteristics = characteristics;
            mContext = context;
            mReader = reader;
        }

        @Override
        public void run() {
            boolean success = false;
            int format = mImage.getFormat();
            switch(format) {
                case ImageFormat.JPEG: {
                    ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();
                    byte[] bytes = new byte[buffer.remaining()];
                    buffer.get(bytes);
                    FileOutputStream output = null;
                    try {
                        output = new FileOutputStream(mFile);
                        output.write(bytes);
                        success = true;
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        mImage.close();
                        closeOutput(output);
                    }
                    break;
                }
                case ImageFormat.RAW_SENSOR: {
                    DngCreator dngCreator = new DngCreator(mCharacteristics, mCaptureResult);
                    FileOutputStream output = null;
                    try {
                        output = new FileOutputStream(mFile);
                        dngCreator.writeImage(output, mImage);
                        success = true;
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        mImage.close();
                        closeOutput(output);
                    }
                    break;
                }
                default: {
                    Log.e(TAG, "Cannot save image, unexpected image format:" + format);
                    break;
                }
            }

            // Decrement reference count to allow ImageReader to be closed to free up resources.
            mReader.close();

            // If saving the file succeeded, update MediaStore.
            if (success) {
                MediaScannerConnection.scanFile(mContext, new String[] { mFile.getPath()},
                /*mimeTypes*/null, new MediaScannerConnection.MediaScannerConnectionClient() {
                    @Override
                    public void onMediaScannerConnected() {
                        // Do nothing
                    }

                    @Override
                    public void onScanCompleted(String path, Uri uri) {
                        Log.i(TAG, "Scanned " + path + ":");
                        Log.i(TAG, "-> uri=" + uri);
                    }
                });
            }
        }

        /**
         * Builder class for constructing {@link ImageSaver}s.
         *
         * This class is thread safe.
         */
        public static class ImageSaverBuilder {
            private Image mImage;
            private File mFile;
            private CaptureResult mCaptureResult;
            private CameraCharacteristics mCharacteristics;
            private Context mContext;
            private RefCountedAutoCloseable<ImageReader> mReader;

            /**
             * Construct a new ImageSaverBuilder using the given {@link Context}.
             * @param context a {@link Context} to for accessing the
             *                  {@link android.provider.MediaStore}.
             */
            public ImageSaverBuilder(final Context context) {
                mContext = context;
            }

            public synchronized ImageSaverBuilder setRefCountedReader(
                    RefCountedAutoCloseable<ImageReader> reader) {
                if (reader == null ) throw new NullPointerException();

                mReader = reader;
                return this;
            }

            public synchronized ImageSaverBuilder setImage(final Image image) {
                if (image == null) throw new NullPointerException();
                mImage = image;
                return this;
            }

            public synchronized ImageSaverBuilder setFile(final File file) {
                if (file == null) throw new NullPointerException();
                mFile = file;
                return this;
            }

            public synchronized ImageSaverBuilder setResult(final CaptureResult result) {
                if (result == null) throw new NullPointerException();
                mCaptureResult = result;
                return this;
            }

            public synchronized ImageSaverBuilder setCharacteristics(
                    final CameraCharacteristics characteristics) {
                if (characteristics == null) throw new NullPointerException();
                mCharacteristics = characteristics;
                return this;
            }

            public synchronized ImageSaver buildIfComplete() {
                if (!isComplete()) {
                    return null;
                }
                return new ImageSaver(mImage, mFile, mCaptureResult, mCharacteristics, mContext,
                        mReader);
            }

            public synchronized String getSaveLocation() {
                return (mFile == null) ? "Unknown" : mFile.toString();
            }

            private boolean isComplete() {
                return mImage != null && mFile != null && mCaptureResult != null
                        && mCharacteristics != null;
            }
        }
    }

    // Utility classes and methods:
    // *********************************************************************************************

    /**
     * Comparator based on area of the given {@link Size} objects.
     */
    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());
        }

    }

    /**
     * A dialog fragment for displaying non-recoverable errors; this {@ling Activity} will be
     * finished once the dialog has been acknowledged by the user.
     */
    public static class ErrorDialog extends DialogFragment {

        private String mErrorMessage;

        public ErrorDialog() {
            mErrorMessage = "Unknown error occurred!";
        }

        // Build a dialog with a custom message (Fragments require default constructor).
        public static ErrorDialog buildErrorDialog(String errorMessage) {
            ErrorDialog dialog = new ErrorDialog();
            dialog.mErrorMessage = errorMessage;
            return dialog;
        }

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

    /**
     * A wrapper for an {@link AutoCloseable} object that implements reference counting to allow
     * for resource management.
     */
    public static class RefCountedAutoCloseable<T extends AutoCloseable> implements AutoCloseable {
        private T mObject;
        private long mRefCount = 0;

        /**
         * Wrap the given object.
         * @param object an object to wrap.
         */
        public RefCountedAutoCloseable(T object) {
            if (object == null) throw new NullPointerException();
            mObject = object;
        }

        /**
         * Increment the reference count and return the wrapped object.
         *
         * @return the wrapped object, or null if the object has been released.
         */
        public synchronized T getAndRetain() {
            if (mRefCount < 0) {
                return null;
            }
            mRefCount++;
            return mObject;
        }

        /**
         * Return the wrapped object.
         *
         * @return the wrapped object, or null if the object has been released.
         */
        public synchronized T get() {
            return mObject;
        }

        /**
         * Decrement the reference count and release the wrapped object if there are no other
         * users retaining this object.
         */
        @Override
        public synchronized void close() {
            if (mRefCount >= 0) {
                mRefCount--;
                if (mRefCount < 0) {
                    try {
                        mObject.close();
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    } finally {
                        mObject = null;
                    }
                }
            }
        }
    }

    /**
     * Given {@code choices} of {@code Size}s supported by a camera, chooses the smallest one whose
     * width and height are at least as large as the respective requested values, 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 width       The minimum desired width
     * @param height      The minimum desired height
     * @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 width, int height, Size aspectRatio) {
        // Collect the supported resolutions that are at least as big as the preview Surface
        List<Size> bigEnough = new ArrayList<>();
        int w = aspectRatio.getWidth();
        int h = aspectRatio.getHeight();
        for (Size option : choices) {
            if (option.getHeight() == option.getWidth() * h / w &&
                    option.getWidth() >= width && option.getHeight() >= height) {
                bigEnough.add(option);
            }
        }

        // Pick the smallest of those, assuming we found any
        if (bigEnough.size() > 0) {
            return Collections.min(bigEnough, new CompareSizesByArea());
        } else {
            Log.e(TAG, "Couldn't find any suitable preview size");
            return choices[0];
        }
    }

    /**
     * Generate a string containing a formatted timestamp with the current date and time.
     *
     * @return a {@link String} representing a time.
     */
    private static String generateTimestamp() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy_MM_dd_HH_mm_ss_SSS", Locale.US);
        return sdf.format(new Date());
    }

    /**
     * Cleanup the given {@link OutputStream}.
     *
     * @param outputStream the stream to close.
     */
    private static void closeOutput(OutputStream outputStream) {
        if (null != outputStream) {
            try {
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Return true if the given array contains the given integer.
     *
     * @param modes array to check.
     * @param mode integer to get for.
     * @return true if the array contains the given integer, otherwise false.
     */
    private static boolean contains(int[] modes, int mode) {
        if (modes == null) {
            return false;
        }
        for (int i : modes) {
            if (i == mode) {
                return true;
            }
        }
        return false;
    }

    /**
     * Return true if the two given {@link Size}s have the same aspect ratio.
     *
     * @param a first {@link Size} to compare.
     * @param b second {@link Size} to compare.
     * @return true if the sizes have the same aspect ratio, otherwise false.
     */
    private static boolean checkAspectsEqual(Size a, Size b) {
        double aAspect = a.getWidth() / (double) a.getHeight();
        double bAspect = b.getWidth() / (double) b.getHeight();
        return Math.abs(aAspect - bAspect) <= ASPECT_RATIO_TOLERANCE;
    }

    /**
     * Rotation need to transform from the camera sensor orientation to the device's current
     * orientation.
     * @param c the {@link CameraCharacteristics} to query for the camera sensor orientation.
     * @param deviceOrientation the current device orientation relative to the native device
     *                          orientation.
     * @return the total rotation from the sensor orientation to the current device orientation.
     */
    private static int sensorToDeviceRotation(CameraCharacteristics c, int deviceOrientation) {
        int sensorOrientation = c.get(CameraCharacteristics.SENSOR_ORIENTATION);

        // Get device orientation in degrees
        deviceOrientation = ORIENTATIONS.get(deviceOrientation);

        // Reverse device orientation for front-facing cameras
        if (c.get(CameraCharacteristics.LENS_FACING) == CameraCharacteristics.LENS_FACING_FRONT) {
            deviceOrientation = -deviceOrientation;
        }

        // Calculate desired JPEG orientation relative to camera orientation to make
        // the image upright relative to the device orientation
        return (sensorOrientation + deviceOrientation + 360) % 360;
    }

    /**
     * Shows a {@link Toast} on the UI thread.
     *
     * @param text The message to show.
     */
    private void showToast(String text) {
        // We show a Toast by sending request message to mMessageHandler. This makes sure that the
        // Toast is shown on the UI thread.
        Message message = Message.obtain();
        message.obj = text;
        mMessageHandler.sendMessage(message);
    }

    /**
     * If the given request has been completed, remove it from the queue of active requests and
     * send an {@link ImageSaver} with the results from this request to a background thread to
     * save a file.
     *
     * Call this only with {@link #mCameraStateLock} held.
     *
     * @param requestId the ID of the {@link CaptureRequest} to handle.
     * @param builder the {@link ImageSaver.ImageSaverBuilder} for this request.
     * @param queue the queue to remove this request from, if completed.
     */
    private void handleCompletionLocked(int requestId, ImageSaver.ImageSaverBuilder builder,
                                        TreeMap<Integer, ImageSaver.ImageSaverBuilder> queue) {
        if (builder == null) return;
        ImageSaver saver = builder.buildIfComplete();
        if (saver != null) {
            queue.remove(requestId);
            AsyncTask.THREAD_POOL_EXECUTOR.execute(saver);
        }
    }

    /**
     * Check if we are using a device that only supports the LEGACY hardware level.
     *
     * Call this only with {@link #mCameraStateLock} held.
     *
     * @return true if this is a legacy device.
     */
    private boolean isLegacyLocked() {
        return mCharacteristics.get(CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL) ==
                CameraCharacteristics.INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY;
    }

    /**
     * Start the timer for the pre-capture sequence.
     *
     * Call this only with {@link #mCameraStateLock} held.
     */
    private void startTimerLocked() {
        mCaptureTimer = SystemClock.elapsedRealtime();
    }

    /**
     * Check if the timer for the pre-capture sequence has been hit.
     *
     * Call this only with {@link #mCameraStateLock} held.
     *
     * @return true if the timeout occurred.
     */
    private boolean hitTimeoutLocked() {
        return (SystemClock.elapsedRealtime() - mCaptureTimer) > PRECAPTURE_TIMEOUT_MS;
    }

    // *********************************************************************************************

}