/*
 * Copyright 2014 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 org.tensorflow.demo;

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.content.res.Configuration;
import android.graphics.ImageFormat;
import android.graphics.Matrix;
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.CaptureResult;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.ImageReader;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.util.Size;
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 org.tensorflow.demo.env.Logger;

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;

public class CameraConnectionFragment extends Fragment {
  private static final Logger LOGGER = new Logger();

  /**
   * The camera preview size will be chosen to be the smallest frame by pixel size capable of
   * containing a DESIRED_SIZE x DESIRED_SIZE square.
   */
  private static final int MINIMUM_PREVIEW_SIZE = 320;

  private RecognitionScoreView scoreView;

  /**
   * Conversion from screen rotation to JPEG orientation.
   */
  private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
  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);
  }

  /**
   * {@link android.view.TextureView.SurfaceTextureListener} handles several lifecycle events on a
   * {@link TextureView}.
   */
  private final TextureView.SurfaceTextureListener surfaceTextureListener =
      new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(
            final SurfaceTexture texture, final int width, final int height) {
          openCamera(width, height);
        }

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

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

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

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

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

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

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

  /**
   * The rotation in degrees of the camera sensor from the display. 
   */
  private Integer sensorOrientation;
  
  /**
   * The {@link android.util.Size} of camera preview.
   */
  private Size previewSize;

  /**
   * {@link android.hardware.camera2.CameraDevice.StateCallback}
   * is called when {@link CameraDevice} changes its state.
   */
  private final CameraDevice.StateCallback stateCallback =
      new CameraDevice.StateCallback() {
        @Override
        public void onOpened(final CameraDevice cd) {
          // This method is called when the camera is opened.  We start camera preview here.
          cameraOpenCloseLock.release();
          cameraDevice = cd;
          createCameraPreviewSession();
        }

        @Override
        public void onDisconnected(final CameraDevice cd) {
          cameraOpenCloseLock.release();
          cd.close();
          cameraDevice = null;
        }

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

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

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

  /**
   * An additional thread for running inference so as not to block the camera.
   */
  private HandlerThread inferenceThread;

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

  /**
   * An {@link ImageReader} that handles preview frame capture.
   */
  private ImageReader previewReader;

  /**
   * {@link android.hardware.camera2.CaptureRequest.Builder} for the camera preview
   */
  private CaptureRequest.Builder previewRequestBuilder;

  /**
   * {@link CaptureRequest} generated by {@link #previewRequestBuilder}
   */
  private CaptureRequest previewRequest;

  /**
   * A {@link Semaphore} to prevent the app from exiting before closing the camera.
   */
  private final Semaphore cameraOpenCloseLock = 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, 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(
      final Size[] choices, final int width, final int height, final Size aspectRatio) {
    // Collect the supported resolutions that are at least as big as the preview Surface
    final List<Size> bigEnough = new ArrayList<Size>();
    for (final Size option : choices) {
      if (option.getHeight() >= MINIMUM_PREVIEW_SIZE && option.getWidth() >= MINIMUM_PREVIEW_SIZE) {
        LOGGER.i("Adding size: " + option.getWidth() + "x" + option.getHeight());
        bigEnough.add(option);
      } else {
        LOGGER.i("Not adding size: " + option.getWidth() + "x" + option.getHeight());
      }
    }

    // Pick the smallest of those, assuming we found any
    if (bigEnough.size() > 0) {
      final Size chosenSize = Collections.min(bigEnough, new CompareSizesByArea());
      LOGGER.i("Chosen size: " + chosenSize.getWidth() + "x" + chosenSize.getHeight());
      return chosenSize;
    } else {
      LOGGER.e("Couldn't find any suitable preview size");
      return choices[0];
    }
  }

  public static CameraConnectionFragment newInstance() {
    return new CameraConnectionFragment();
  }

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

  @Override
  public void onViewCreated(final View view, final Bundle savedInstanceState) {
    textureView = (AutoFitTextureView) view.findViewById(R.id.texture);
    scoreView = (RecognitionScoreView) view.findViewById(R.id.results);
  }

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

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

    // 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 (textureView.isAvailable()) {
      openCamera(textureView.getWidth(), textureView.getHeight());
    } else {
      textureView.setSurfaceTextureListener(surfaceTextureListener);
    }
  }

  @Override
  public void onPause() {
    closeCamera();
    stopBackgroundThread();
    super.onPause();
  }

  /**
   * 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
   */
  private void setUpCameraOutputs(final int width, final int height) {
    final Activity activity = getActivity();
    final CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    try {
      for (final String cameraId : manager.getCameraIdList()) {
        final CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

        // We don't use a front facing camera in this sample.
        final Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
        if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
          continue;
        }

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

        if (map == null) {
          continue;
        }

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

        sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
        
        // 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.
        previewSize =
            chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class), width, height, largest);

        // We fit the aspect ratio of TextureView to the size of preview we picked.
        final int orientation = getResources().getConfiguration().orientation;
        if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
          textureView.setAspectRatio(previewSize.getWidth(), previewSize.getHeight());
        } else {
          textureView.setAspectRatio(previewSize.getHeight(), previewSize.getWidth());
        }

        CameraConnectionFragment.this.cameraId = cameraId;
        return;
      }
    } catch (final CameraAccessException e) {
      LOGGER.e(e, "Exception!");
    } catch (final NullPointerException e) {
      // Currently an NPE is thrown when the Camera2API is used but not supported on the
      // device this code runs.
      ErrorDialog.newInstance(getString(R.string.camera_error))
          .show(getChildFragmentManager(), FRAGMENT_DIALOG);
    }
  }

  /**
   * Opens the camera specified by {@link CameraConnectionFragment#cameraId}.
   */
  private void openCamera(final int width, final int height) {
    setUpCameraOutputs(width, height);
    configureTransform(width, height);
    final Activity activity = getActivity();
    final CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    try {
      if (!cameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
        throw new RuntimeException("Time out waiting to lock camera opening.");
      }
      manager.openCamera(cameraId, stateCallback, backgroundHandler);
    } catch (final CameraAccessException e) {
      LOGGER.e(e, "Exception!");
    } catch (final InterruptedException e) {
      throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
    }
  }

  /**
   * Closes the current {@link CameraDevice}.
   */
  private void closeCamera() {
    try {
      cameraOpenCloseLock.acquire();
      if (null != captureSession) {
        captureSession.close();
        captureSession = null;
      }
      if (null != cameraDevice) {
        cameraDevice.close();
        cameraDevice = null;
      }
      if (null != previewReader) {
        previewReader.close();
        previewReader = null;
      }
    } catch (final InterruptedException e) {
      throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
    } finally {
      cameraOpenCloseLock.release();
    }
  }

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

    inferenceThread = new HandlerThread("InferenceThread");
    inferenceThread.start();
    inferenceHandler = new Handler(inferenceThread.getLooper());
  }

  /**
   * Stops the background thread and its {@link Handler}.
   */
  private void stopBackgroundThread() {
    backgroundThread.quitSafely();
    inferenceThread.quitSafely();
    try {
      backgroundThread.join();
      backgroundThread = null;
      backgroundHandler = null;

      inferenceThread.join();
      inferenceThread = null;
      inferenceThread = null;
    } catch (final InterruptedException e) {
      LOGGER.e(e, "Exception!");
    }
  }

  private final TensorFlowImageListener tfPreviewListener = new TensorFlowImageListener();

  private final CameraCaptureSession.CaptureCallback captureCallback =
      new CameraCaptureSession.CaptureCallback() {
        @Override
        public void onCaptureProgressed(
            final CameraCaptureSession session,
            final CaptureRequest request,
            final CaptureResult partialResult) {}

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

  /**
   * Creates a new {@link CameraCaptureSession} for camera preview.
   */
  private void createCameraPreviewSession() {
    try {
      final SurfaceTexture texture = textureView.getSurfaceTexture();
      assert texture != null;

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

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

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

      LOGGER.i("Opening camera preview: " + previewSize.getWidth() + "x" + previewSize.getHeight());

      // Create the reader for the preview frames.
      previewReader =
          ImageReader.newInstance(
              previewSize.getWidth(), previewSize.getHeight(), ImageFormat.YUV_420_888, 2);

      previewReader.setOnImageAvailableListener(tfPreviewListener, backgroundHandler);
      previewRequestBuilder.addTarget(previewReader.getSurface());

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

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

              // When the session is ready, we start displaying the preview.
              captureSession = cameraCaptureSession;
              try {
                // Auto focus should be continuous for camera preview.
                previewRequestBuilder.set(
                    CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                // Flash is automatically enabled when necessary.
                previewRequestBuilder.set(
                    CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

                // Finally, we start displaying the camera preview.
                previewRequest = previewRequestBuilder.build();
                captureSession.setRepeatingRequest(
                    previewRequest, captureCallback, backgroundHandler);
              } catch (final CameraAccessException e) {
                LOGGER.e(e, "Exception!");
              }
            }

            @Override
            public void onConfigureFailed(final CameraCaptureSession cameraCaptureSession) {
              showToast("Failed");
            }
          },
          null);
    } catch (final CameraAccessException e) {
      LOGGER.e(e, "Exception!");
    }

    LOGGER.i("Getting assets.");
    tfPreviewListener.initialize(
        getActivity().getAssets(), scoreView, inferenceHandler, sensorOrientation);
    LOGGER.i("TensorFlow initialized.");
  }

  /**
   * Configures the necessary {@link android.graphics.Matrix} transformation to `mTextureView`.
   * This method should be called after the camera preview size is determined in
   * setUpCameraOutputs and also the size of `mTextureView` is fixed.
   *
   * @param viewWidth  The width of `mTextureView`
   * @param viewHeight The height of `mTextureView`
   */
  private void configureTransform(final int viewWidth, final int viewHeight) {
    final Activity activity = getActivity();
    if (null == textureView || null == previewSize || null == activity) {
      return;
    }
    final int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
    final Matrix matrix = new Matrix();
    final RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
    final RectF bufferRect = new RectF(0, 0, previewSize.getHeight(), previewSize.getWidth());
    final float centerX = viewRect.centerX();
    final 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);
      final float scale =
          Math.max(
              (float) viewHeight / previewSize.getHeight(),
              (float) viewWidth / previewSize.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);
    }
    textureView.setTransform(matrix);
  }

  /**
   * Compares two {@code Size}s based on their areas.
   */
  static class CompareSizesByArea implements Comparator<Size> {
    @Override
    public int compare(final Size lhs, final 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(final String message) {
      final ErrorDialog dialog = new ErrorDialog();
      final Bundle args = new Bundle();
      args.putString(ARG_MESSAGE, message);
      dialog.setArguments(args);
      return dialog;
    }

    @Override
    public Dialog onCreateDialog(final 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(final DialogInterface dialogInterface, final int i) {
                  activity.finish();
                }
              })
          .create();
    }
  }
}
