SaveAssetLibrary.m

#import <React/RCTBridgeModule.h>
#import <Photos/Photos.h>
#import <UIKit/UIKit.h>
#import <React/RCTLog.h>

@interface SaveAssetLibrary : NSObject <RCTBridgeModule>
@end

@implementation SaveAssetLibrary

NSMapTable *_successCallbacks;

RCT_EXPORT_MODULE();

RCT_EXPORT_METHOD(saveImage:(NSDictionary *)obj successCallback:(RCTResponseSenderBlock)successCallback errorCallback:(RCTResponseErrorBlock)errorCallback)
{
  if (!_successCallbacks) {
    _successCallbacks = [NSMapTable strongToStrongObjectsMapTable];
  }

  NSString *imagePath = obj[@"imagePath"];
  NSString *imageName = obj[@"imageName"];
  NSString *imageType = obj[@"imageType"];
  int width =  [obj[@"width"] intValue];
  int height =  [obj[@"height"] intValue];

  // Create NSURL from uri
  NSURL *url = [[NSURL alloc] initWithString:imagePath];

  PHFetchResult *result = [PHAsset fetchAssetsWithALAssetURLs:@[url] options:nil];
  PHAsset *asset = result.firstObject;

  if (asset) {
    PHCachingImageManager *imageManager = [[PHCachingImageManager alloc] init];

    PHImageRequestOptions *option = [PHImageRequestOptions new];
    option.synchronous = YES;

    [_successCallbacks setObject:successCallback forKey:imageManager];
    // Request an image for the asset from the PHCachingImageManager.
    [imageManager requestImageForAsset:asset targetSize:CGSizeMake(width, height) contentMode:PHImageContentModeAspectFit options:option
                         resultHandler:^(UIImage *image, NSDictionary *info)
     {
       NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
       NSString * basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;

       NSData * binaryImageData;
       if([imageType isEqualToString:@"png"]) {
         binaryImageData = UIImagePNGRepresentation(image);
       } else {
         binaryImageData = UIImageJPEGRepresentation(image, 1.0);
       }
       NSString *imageNameWithExtension = [NSString stringWithFormat:@"%@.%@", imageName, imageType];
       [binaryImageData writeToFile:[basePath stringByAppendingPathComponent:imageNameWithExtension] atomically:YES];

       // Call the callback
       RCTResponseSenderBlock successCallback = [_successCallbacks objectForKey:imageManager];
       if (successCallback) {
         successCallback(@[[basePath stringByAppendingPathComponent:imageNameWithExtension]]);
         [_successCallbacks removeObjectForKey:imageManager];
       } else {
         RCTLogWarn(@"No callback registered for success");
       }
     }
     ];
  } else {
    // Check if the photo is in the photo stream
    NSString *localIDFragment = [[[[imagePath componentsSeparatedByString: @"="] objectAtIndex: 1] componentsSeparatedByString: @"&"] objectAtIndex: 0];
    PHFetchResult *fetchResultForPhotostream = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumMyPhotoStream options: nil];
    
    if (fetchResultForPhotostream.count > 0) {
      PHAssetCollection *photostream = fetchResultForPhotostream [0];
      
      PHFetchOptions *optionsForFetch = [[PHFetchOptions alloc] init];;
      optionsForFetch.includeHiddenAssets = YES;
      PHFetchResult *fetchResultForPhotostreamAssets = [PHAsset fetchAssetsInAssetCollection:photostream options:optionsForFetch];
      
      if (fetchResultForPhotostreamAssets.count > 0) {
        NSIndexSet *i = [NSIndexSet indexSetWithIndexesInRange: NSMakeRange(0, fetchResultForPhotostreamAssets.count)];
        //let i=NSIndexSet(indexesInRange: NSRange(location: 0,length: fetchResultForPhotostreamAssets.count))
        
        [_successCallbacks setObject:successCallback forKey:photostream];
        [fetchResultForPhotostreamAssets enumerateObjectsAtIndexes: i options: NSEnumerationReverse usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
          PHAsset *target = obj;
          NSString *identifier = target.localIdentifier;
          if ([identifier rangeOfString: localIDFragment].length != 0) {
            if (target) {
              // get photo info from this asset
              PHImageRequestOptions * imageRequestOptions = [[PHImageRequestOptions alloc] init];
              imageRequestOptions.synchronous = YES;
              [[PHImageManager defaultManager]
               requestImageDataForAsset:target
               options:imageRequestOptions
               resultHandler:^(NSData *imageData, NSString *dataUTI,
                               UIImageOrientation orientation,
                               NSDictionary *info)
               {
                 if ([info objectForKey:@"PHImageFileURLKey"]) {
                   
                   NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
                   NSString * basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
                   
                   NSString *imageNameWithExtension = [NSString stringWithFormat:@"%@.%@", imageName, imageType];
                   [imageData writeToFile:[basePath stringByAppendingPathComponent:imageNameWithExtension] atomically:YES];
                   // Call the callback
                   RCTResponseSenderBlock successCallback = [_successCallbacks objectForKey:photostream];
                   if (successCallback) {
                       successCallback(@[[basePath stringByAppendingPathComponent:imageNameWithExtension]]);
                       [_successCallbacks removeObjectForKey:photostream];
                   } else {
                     RCTLogWarn(@"No callback registered for success");
                   }
                 }
               }];
            }
          }
        }];
      }
    }
  }
}

@end