Create the perflab_job_regenerate_images action to handle image regeneration within the background process. This action will be called by the background processing infrastructure. Code for the background job should be written in a new module file module/images/regenerate-existing-images/regenerate-existing-images-job.php.

Acceptance Criteria

• Create a new function registered to the perflab_job_regenerate_images action.
• The function will accept the following parameters
  • $job_id - The term ID for the current Regenerate Images background job
  • $job_data - The job data array for the current Regenerate Images background job
• The function will run a WP_Query to retrieve the attachment IDs to run. The query will use the following parameters:
  • post_type: attachment
  • fields: ids
  • posts_per_page: 5
  • The query will include the following tax_query

array(
   'taxonomy' => 'background_job',
   'field'    => 'term_id',
   'terms'    => $job_id,
   'operator' => ‘NOT IN’,
)

• Using the attachment IDs returned from the WP_Query, the function will loop through the attachment IDs and regenerate each image one by one.
  • Backup the sizes found in the wp_get_attachment_metadata in a new _backup_image_sizes post meta
  • Backup the sources found in the wp_get_attachment_metadata in a new _backup_image_sources post meta
  • Unset the sources and sizes metadata in the wp_update_attachment_metadata
  • Get an array of the images sizes using wp_get_missing_image_subsizes
  • Loop over each image size returned and do the following:
    • Create the new image size using the wp_get_image_editor
    • Create additional sources for the image size using the image editor
    • On success, update the newly created image size in the attachment metadata with wp_update_attachment_metadata
    • On failure, Update the attachment post meta _regenerate_failures and increment the count
    • If the _regenerate_failures meta count reaches 8 retries:
      • Add the job term to the attachment with wp_set_object_terms using the $job_id
      • Backfill all previous sizes and sources metadata using the backup metadata (_backup_image_sizes and _backup_image_sources)
  • Once all image sizes have been successfully updated
    • Check the value of the delete_images key in the $job_data. If the value is true, delete the old image files using the backup metadata for reference
    • Add the job term to the attachment with wp_set_object_terms using the $job_id
    • Delete the backup metadata from the attachment (_backup_image_sizes and _backup_image_sources)