polevaultweb/wpos3-relative-url-find-replace.php

## wpos3-relative-url-find-replace.php
<?php
/*
Plugin Name: WP Offload S3 - Relative URL Find & Replace
Description: Find and replace relative local URLs with S3 URLs in post content after they have been uploaded to S3
Author: Delicious Brains
Version: 1.0
Author URI: https://deliciousbrains.com/
*/

add_action( 'admin_init', 'wpos3rel_find_replace' );
add_filter( 'query', 'wpos3rel_find_replace_strip_local_url' );

/**
 * Run a find and replace on all attachments uploaded to S3
 */
function wpos3rel_find_replace() {
	if ( ! class_exists( 'Amazon_S3_And_CloudFront_Pro' ) ) {
		return;
	}

	if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
		return;
	}

	global $pagenow;
	if ( 'post.php' === $pagenow ) {
		// Don't run on the post page, creates a loop
		return;
	}

	global $as3cfpro;

	if ( ! $as3cfpro->get_setting( 'serve-from-s3' ) ) {
		// Don't replace if we aren't rewriting URLs
		return;
	}

	if ( ! get_site_option( 'wpos3rel_find_replace', false ) ) {
		$blogs = $as3cfpro->get_blogs_data();

		// Get all uploaded S3 attachments IDs
		foreach ( $blogs as $blog_id => $blog ) {

			$attachments = $as3cfpro->get_all_s3_attachments( $blog['prefix'] );

			$as3cfpro->switch_to_blog( $blog_id );

			foreach ( $attachments as $attachment ) {
				$as3cfpro->find_and_replace_attachment_urls( $attachment['post_id'] );
			}
		}

		$as3cfpro->restore_current_blog( $blog_id );

		// Make sure this doesn't get run again, unless we clear this option
		update_site_option( 'wpos3rel_find_replace', true );
	}
}

/**
 * Remove the site home URL from local URLs during find and replace
 * so they become relative
 *
 * @param string $query
 *
 * @return string mixed
 */
function wpos3rel_find_replace_strip_local_url( $query ) {
	$callers       = debug_backtrace();
	$parent_method = false;
	$child_method  = false;

	foreach ( $callers as $caller ) {
		if ( isset( $caller['function'] ) && 'wpos3rel_find_replace' === $caller['function'] ) {
			$parent_method = true;
		}

		if ( isset( $caller['function'] ) && 'process_pair_replacement' === $caller['function'] ) {
			$child_method = true;
		}
	}

	if ( $parent_method && $child_method ) {
		// Remove the root URL of the site from any local URL being replaced
		$query = str_replace( untrailingslashit( network_home_url() ), '', $query );
	}

	return $query;
}