Image_Import::set_featured_image( bool $refresh = false )

	public function set_featured_image( $refresh = false ){
		if( !$this->video_post->video_id ){
			return;
		}

		Helper::debug_message(
			sprintf(
				'Preparing to import featured image for post ID #%d.',
				$this->video_post->get_post()->ID
			)
		);

		if( $refresh ){
			$result = $this->import_from_api();
		}else{

			$args = [
				'post_type' => 'attachment',
				'meta_key'  	=> 'video_thumbnail',
				'meta_value'	=> $this->video_post->video_id
			];

			if( !empty( $this->video_post->image_uri ) ){
				$args['meta_key'] = '__vimeo_image_uri';
				$args['meta_value']  = $this->video_post->image_uri;
			}

			// check if thumbnail was already imported
			$attachment = get_posts( $args );
			// if thumbnail exists, return it
			if( $attachment ){
				// set image as featured for current post
				set_post_thumbnail( $this->video_post->get_post()->ID, $attachment[0]->ID );

				Helper::debug_message(
					sprintf(
						'An existing attachment having ID %d was detected and was set as featured image for post ID %d.',
						$attachment[0]->ID,
						$this->video_post->get_post()->ID
					)
				);

				$result = [
					'post_id' 		=> $this->video_post->get_post()->ID,
					'attachment_id' => $attachment[0]->ID
				];
			}else{
				$image_url = end( $this->video_post->thumbnails );
				$result = $this->import_to_media( $image_url );

				if( isset( $result['attachment_id'] ) && !empty( $this->video_post->image_uri ) ){
					update_post_meta(
						$result['attachment_id'],
						'__vimeo_image_uri',
						$this->video_post->image_uri
					);
				}

			}
		}

		if( !$result ){
			Helper::debug_message(
				'Error, the featured image was not imported.'
			);
		}

		return $result;
	}