/*
 *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#import "AVCaptureSession+DevicePosition.h"

BOOL CFStringContainsString(CFStringRef theString, CFStringRef stringToFind) {
  return CFStringFindWithOptions(theString,
                                 stringToFind,
                                 CFRangeMake(0, CFStringGetLength(theString)),
                                 kCFCompareCaseInsensitive,
                                 nil);
}

@implementation AVCaptureSession (DevicePosition)

+ (AVCaptureDevicePosition)devicePositionForSampleBuffer:
    (CMSampleBufferRef)sampleBuffer {
  // Check the image's EXIF for the camera the image came from.
  AVCaptureDevicePosition cameraPosition = AVCaptureDevicePositionUnspecified;
  CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(
      kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate);
  if (attachments) {
    int size = CFDictionaryGetCount(attachments);
    if (size > 0) {
      CFDictionaryRef cfExifDictVal = nil;
      if (CFDictionaryGetValueIfPresent(attachments,
                                        (const void *)CFSTR("{Exif}"),
                                        (const void **)&cfExifDictVal)) {
        CFStringRef cfLensModelStrVal;
        if (CFDictionaryGetValueIfPresent(cfExifDictVal,
                                          (const void *)CFSTR("LensModel"),
                                          (const void **)&cfLensModelStrVal)) {
          if (CFStringContainsString(cfLensModelStrVal, CFSTR("front"))) {
            cameraPosition = AVCaptureDevicePositionFront;
          } else if (CFStringContainsString(cfLensModelStrVal, CFSTR("back"))) {
            cameraPosition = AVCaptureDevicePositionBack;
          }
        }
      }
    }
    CFRelease(attachments);
  }
  return cameraPosition;
}

@end