Image Plugin — Need Guidance

Hi All,

We’re writing a small plugin for WordPress that will sit in between when a user publishes a blog post and when its saved to the DB.

Process flow:
1. User creates new blog post
2. User clicks publish
3. The plugin will sift through the body looking for URLs which points to a JPG image.
4. If the plugin finds any, it will download it to the server and store it in the WP database as an attachment.
5. After its done, it returns control back to WP to continue.

I essentially know how to do most of the above. My question is what type of filter and here does it hook into during the publish process?

I’ve written other plugins but they all affect the forward-facing side of the blog, not the admin part.

Any links or guidance is greatly appreciated.

Best,
Cent