get_post_gallery with Gutenberg

I have a site where I created a page that takes the gallery images from a post and puts them into a slider.

I used the following code:

// gets the gallery info
$gallery = get_post_gallery( $post->ID, false );
// makes an array of image ids
$ids = explode ( ",", $gallery['ids'] );

Then I inserted the images using wp_get_attachment_image().

Unfortunately, with WP 5.0 and Gutenberg, get_post_gallery no longer works with newly added content. It seems that get_post_gallery used a shortcode that no longer works with Gutenberg.

I am still getting up to speed on Gutenberg and the block system. Until I understand that all better, I was wondering if anyone has any advice on how to get the image ids from a gallery in Gutenberg?

Using birgire’s suggestions, I came up with the following solution that is working well with both the old pre-WP 4.x data and the newer posts that have been added under 5.0.

// if there is a gallery block do this
if (has_block('gallery', $post->post_content)) {
    $post_blocks = parse_blocks($post->post_content);
    $ids = $post_blocks[0][attrs][ids];
} 
// if there is not a gallery block do this
else {
    // gets the gallery info
    $gallery = get_post_gallery( $post->ID, false );
    // makes an array of image ids
    $ids = explode ( ",", $gallery['ids'] );
}