RNMediaMeta.m

#import "RNMediaMeta.h"

static NSArray *metadatas;
@implementation RNMediaMeta

- (NSArray *)metadatas
{
  if (!metadatas) {
    metadatas = @[
      @"albumName",
      @"artist",
      @"comment",
      @"copyrights",
      @"creationDate",
      @"date",
      @"encodedby",
      @"genre",
      @"language",
      @"location",
      @"lastModifiedDate",
      @"performer",
      @"publisher",
      @"title"
    ];
  }
  return metadatas;
}

RCT_EXPORT_MODULE()

- (dispatch_queue_t)methodQueue
{
  return dispatch_queue_create("com.mybigday.rn.MediaMetaQueue", DISPATCH_QUEUE_SERIAL);
}

RCT_EXPORT_METHOD(get:(NSString *)path
                  withOptions:(NSDictionary *)options
                  resolver:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)
{
  NSFileManager *fileManager = [NSFileManager defaultManager];

  BOOL isDir;
  if (![fileManager fileExistsAtPath:path isDirectory:&isDir] || isDir){
    NSError *err = [NSError errorWithDomain:@"file not found" code:-15 userInfo:nil];
    reject([NSString stringWithFormat: @"%lu", (long)err.code], err.localizedDescription, err);
    return;
  }

  NSMutableDictionary *result = [NSMutableDictionary new];
  NSDictionary *assetOptions = @{AVURLAssetPreferPreciseDurationAndTimingKey: @YES};
  AVURLAsset *asset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:path] options:assetOptions];

  NSArray *keys = [NSArray arrayWithObjects:@"commonMetadata", nil];
  [asset loadValuesAsynchronouslyForKeys:keys completionHandler:^{
    // string keys
    for (NSString *key in [self metadatas]) {
      NSArray *items = [AVMetadataItem metadataItemsFromArray:asset.commonMetadata
                                                     withKey:key
                                                    keySpace:AVMetadataKeySpaceCommon];
      for (AVMetadataItem *item in items) {
        [result setObject:item.value forKey:key];
      }
    }

    if (options[@"getThumb"]) {
      UIImage *thumbnail;
      NSArray *artworks = [AVMetadataItem metadataItemsFromArray:asset.commonMetadata
                                                        withKey:AVMetadataCommonKeyArtwork
                                                        keySpace:AVMetadataKeySpaceCommon];
      // artwork thumb
      for (AVMetadataItem *item in artworks) {
        thumbnail = [UIImage imageWithData:item.value];
      }
      if (thumbnail) {
        [result setObject:@(thumbnail.size.width) forKey:@"width"];
        [result setObject:@(thumbnail.size.height) forKey:@"height"];
        NSString *data = [UIImagePNGRepresentation(thumbnail) base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
        [result setObject:data
                  forKey:@"thumb"];
      }

      // video frame thumb
      AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc]initWithAsset:asset];
      imageGenerator.appliesPreferredTrackTransform = YES;
      CMTime duration = [asset duration];
      CMTime time = CMTimeMake(duration.value / 2, duration.timescale);

      CGImageRef imageRef = [imageGenerator copyCGImageAtTime:time actualTime:NULL error:NULL];
      thumbnail = [UIImage imageWithCGImage:imageRef];
      if (thumbnail) {
        [result setObject:@(thumbnail.size.width) forKey:@"width"];
        [result setObject:@(thumbnail.size.height) forKey:@"height"];
        [result setObject:@((CMTimeGetSeconds(asset.duration) * 1000)) forKey:@"duration"];
        
        NSString *data = [UIImagePNGRepresentation(thumbnail) base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
        [result setObject:data
                  forKey:@"thumb"];
      }
      CGImageRelease(imageRef);
    }

    resolve(result);
  }];
}

@end