@property (strong, nonatomic) AVAudioEngine * audioEngine;
@property (strong, nonatomic) SFSpeechRecognizer * speechRecognizer;
@property (strong, nonatomic) SFSpeechAudioBufferRecognitionRequest * request;
@property (strong, nonatomic) SFSpeechRecognitionTask * recognitionTask;
@property (strong, nonatomic) AVAudioInputNode * node;

- (void) initialization {
self.audioEngine = [[AVAudioEngine alloc] init];

NSLocale * local = [[NSLocale alloc] initWithLocaleIdentifier:@"ru_RU"];
self.speechRecognizer = [[SFSpeechRecognizer alloc] initWithLocale:local];

[SFSpeechRecognizer requestAuthorization:^(SFSpeechRecognizerAuthorizationStatus status) {
    dispatch_async(dispatch_get_main_queue(), ^{
        switch (status) {
            case SFSpeechRecognizerAuthorizationStatusNotDetermined:
                NSLog(@"SFSpeechRecognizerAuthorizationStatusNotDetermined");
                break;
            case SFSpeechRecognizerAuthorizationStatusRestricted:
                NSLog(@"SFSpeechRecognizerAuthorizationStatusRestricted");
                break;
            case SFSpeechRecognizerAuthorizationStatusDenied:
                NSLog(@"SFSpeechRecognizerAuthorizationStatusDenied");
                break;
            case SFSpeechRecognizerAuthorizationStatusAuthorized:
                NSLog(@"SFSpeechRecognizerAuthorizationStatusAuthorized");
                break;
        }
    });
}];

- (void) startRecognitionWithCompletion:(void(^)(NSString *recodingString))completion {
if (self.request == nil) {
    self.request = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
}
self.node = self.audioEngine.inputNode;
AVAudioFormat * recognitionFormat = [self.node outputFormatForBus:0];

[self.node installTapOnBus:0 bufferSize:1024 format:recognitionFormat block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
    [self.request appendAudioPCMBuffer:buffer];
}];

[self.audioEngine prepare];
[self.audioEngine startAndReturnError:nil];


self.recognitionTask = [self.speechRecognizer recognitionTaskWithRequest:self.request resultHandler:^(SFSpeechRecognitionResult * _Nullable result, NSError * _Nullable error) {
    if (result.bestTranscription != nil) {
        dispatch_async(dispatch_get_main_queue(), ^{
            completion([result.bestTranscription formattedString]);
        });
    } else {
        NSLog(@"%@", [error localizedDescription]);
    }
}];

- (void)stopRecording {
dispatch_async(dispatch_get_main_queue(), ^{
    if(self.audioEngine.isRunning){
        if (self.node == [self.audioEngine inputNode]) {
            [self.node removeTapOnBus:0];
            [self.node reset];
        }
        [self.audioEngine stop];
        [self.request endAudio];
        [self.recognitionTask cancel];
        self.recognitionTask = nil;
        self.request = nil;
    }
});