Custom Post Type Action Hook / Transients - wordpress

Question

This question is in regards to a plug-in I'm developing.
I'm trying to fire a function each time a custom post type called "Product" is added or edited. In particular, I need a hook that fires before the meta boxes load on the add/edit page, but that only fires on that "Product" custom post type's edit page.
The function that will fire makes an API request, and caches the response in a transient.
The reason for the action hook is because in my current code, when the transient has expired, the add/edit page is broken during the first page load. However if you refresh the page after that, it shows up as intended. I'm fairly certain this is happening because the current conditional statement that checks the transient is located inside of the function that generates the meta box. So my theory is if I can set up an action hook to check the transient before the meta box is generated, it might solve the problem.
However I've got a second theory that the problem is being caused because of the time it takes to make the API request and return the response is longer than the time it takes for the page to load. So if there is an action hook that will delay page loading until the function finishes executing it would be an ideal solution, but I don't believe such an action hook exists. I'm not even certain if such a delay is possible.
I'd really appreciate any help or alternative suggestions you guys might have. Thanks for your time guys.
Code Example:
add_action( 'edit_product', 'llc_hook_campaign_find_active' );
function llc_hook_campaign_find_active() {
if (!$t_campaign_find_active){
limelight_cart_campaign_find_active();
return false;
}
}

Answer 1

Since you are using an action hook, it is not waiting for your API response.
Try using a filter hook instead.
Try using wp_insert_post_data
function filter_handler( $data , $postarr ) {
//make your API call, get the response and store it in post meta or data wherever you want
$response = 'your API response';
//e.g. update_post_meta($postarr['ID'], 'meta_key', $response); OR
//$data['post_content'] = $response;
return $data;
}
add_filter( 'wp_insert_post_data', 'filter_handler', '99', 2 );
In your case, following should work -
add_filter( 'wp_insert_post_data', 'llc_hook_campaign_find_active', '99', 2 );
function llc_hook_campaign_find_active( $data , $postarr ) {
if (!$t_campaign_find_active){
limelight_cart_campaign_find_active();
return $data;
}
}

Answer 2

I was able to make the API request before the meta boxes loaded on the Admin Add/Edit screen by using the action filter edit_form_top. That particular action hook is fired as soon as the Add/Edit page for any post/page/custom post type is loaded. In order to narrow it down so that the function only fires on the Add/Edit screen for my "product" custom post type, I used get_current_screen() along with an if statement.
add_action('edit_form_top', 'llc_hook_campaign_find_active');
function llc_hook_campaign_find_active() {
//Fetch current screen information
$screen = get_current_screen();
//Check if post type is "product"
if($screen->post_type == "product") {
//API Request that checks for an existing transient
$t_campaign_find_active = get_transient('campaign_find_active');
if (!$t_campaign_find_active){
limelight_cart_campaign_find_active();
return false;
}
}
}
Works like a charm.