private static IObservable <Preview> LoadPreview(IPreviewLoader previewLoader, PhotoMessageModel model)
        {
            if (model.PhotoData != null)
            {
                return(previewLoader.LoadPreview(model.PhotoData, PreviewQuality.Low)
                       .Concat(previewLoader.LoadPreview(model.PhotoData, PreviewQuality.High)));
            }

            return(Observable.Empty <Preview>());
        }
        private static IObservable <Preview> LoadPreview(IPreviewLoader previewLoader, StickerMessageModel model)
        {
            if (model.StickerData != null)
            {
                if (model.StickerData?.Thumbnail != null)
                {
                    return(previewLoader.LoadPreview(model.StickerData.Thumbnail)
                           .Concat(previewLoader.LoadPreview(model.StickerData)));
                }

                return(previewLoader.LoadPreview(model.StickerData));
            }

            return(Observable.Empty <Preview>());
        }
        private static IObservable <Preview> LoadPreview(IPreviewLoader previewLoader, VideoMessageModel model)
        {
            if (model.VideoData?.Thumbnail != null)
            {
                return(previewLoader.LoadPreview(model.VideoData.Thumbnail));
            }

            return(Observable.Empty <Preview>());
        }
        private static IObservable <Preview> LoadPreview(IPreviewLoader previewLoader, ReplyModel model)
        {
            if (model.PhotoData != null)
            {
                return(previewLoader.LoadPreview(model.PhotoData, PreviewQuality.Low));
            }

            if (model.VideoData?.Thumbnail != null)
            {
                return(previewLoader.LoadPreview(model.VideoData.Thumbnail));
            }

            if (model.StickerData?.Thumbnail != null)
            {
                return(previewLoader.LoadPreview(model.StickerData.Thumbnail));
            }

            return(Observable.Empty <Preview>());
        }