Discarded code that may someday be relevant.

class-content-clean-cli.php

<?php
/**
 * Content Cleanup Filter Commands.
 */
class IOneContentClean extends WPCOM_VIP_CLI_Command {

	/**
	 * Run selected the_content filters and save back to post content.
	 *
	 * ## OPTIONS
	 *
	 * [--dry-run]
	 * : Set dry-run to false to make changes permanent.
	 *
	 * ## EXAMPLES
	 *
	 *     $ wp ione-content-cleanup filter
	 *     $ wp ione-content-cleanup filter --dry-run=false
	 */
	public function filter( $args, $assoc_args ) {
		$dry_run = $this->is_dry_run( $args );

		// Filters that do not require setup.
		$filters = [
			'globalgrind_404_filter_the_content',
			'network_partial_url_filter_replace',
		];

		if ( function_exists( 'ione_handle_legacy_shortcodes' ) ) {
			$filters[] = 'ione_handle_legacy_shortcodes';
		}

		// Set up for other filters.
		if ( class_exists( 'IOne3_Https' ) ) {
			$class_https = ione_singleton( 'IOne3_Https' );
			$class_https->init_hooks();
			$filters[] = [ $class_https, 'adjust_link_scheme' ];
		}

		if ( class_exists( 'iOne3_Image_Date_Filter' ) ) {
			$class_IDF = ione_singleton( 'iOne3_Image_Date_Filter' );
			$filters[] = [ $class_IDF, 'image_date_check_remove' ];
		}

		if ( class_exists( 'iOne_Migrate_Subdomains' ) ) {
			$class_migrate = iOne_Migrate_Subdomains::get_instance();
			$class_migrate->init();
			$filters[] = [ $class_migrate, 'replace_content_urls' ];
		}

		if ( class_exists( 'iOne_Strip_Styles' ) ) {
			$class_strip = ione_singleton( 'iOne_Strip_Styles' );
			$class_strip->init_hooks();
			$filters[] = [ $class_strip, 'filter_the_content' ];
		}

		if ( class_exists( 'Ione3_Check_Body_Headings' ) ) {
			$class_headings = ione_singleton( 'Ione3_Check_Body_Headings' );
			$filters[] = [ $class_headings, 'filter_the_content' ];
		}

		if ( class_exists( 'iOne_Media_Playlist' ) ) {
			add_action( 'ione3-content-clean-cli-post', [ $this, 'remove_attachments' ], 10, 2 );
		}

		// Image removal reporting.
		add_action( 'ione3_image_date_filter_removed', function( $img_url ) use ( $dry_run ) {
			if ( $dry_run ) {
				WP_CLI::log( sprintf( 'Image: %s would be removed from post id: %d', $img_url, get_the_ID() ) );
			} else {
				WP_CLI::log( sprintf( 'Image: %s removed from post id: %d', $img_url, get_the_ID() ) );
			}
		} );

		WP_CLI::log( sprintf( 'Running the following filters on the content of: %s', home_url() ) );
		WP_CLI::log( implode( "\n", $this->list_callbacks( $filters ) ) );

		$this->apply_filters( $filters, $dry_run );
	}

	/**
	 * Convert a list of callables into human readable references.
	 *
	 * @param array $callbacks List of callables.
	 *
	 * @return array
	 */
	protected function list_callbacks( $callbacks ) {
		return array_map( function( $callback ) {
			if ( is_array( $callback ) && ! empty( $callback[1] ) ) {
				return sprintf( '%s::%s', get_class( $callback[0] ), (string) $callback[1] );
			}

			return (string) $callback;
		}, $callbacks );
	}

	/**
	 * Apply the given filters to the content of all posts on the site.
	 *
	 * @param array $filters Array of callables.
	 * @param bool  $dry_run True if not actually making any changes.
	 */
	private function apply_filters( $filters, $dry_run ) {
		if ( $dry_run ) {
			WP_CLI::warning( 'This is a dry-run. Add --dry-run=false to run the actual thing.' );
		}

		$paged = 1;
		$post_types = get_post_types(); // Because 'any' doesn't get all.
		$this->start_bulk_operation();
		do {
			$query = new WP_Query( [
				'posts_per_page' => 100,
				'post_status' => 'any',
				'post_type' => $post_types,
				'paged' => $paged,
				'cache_results' => false,
				'ignore_sticky_posts' => true,
				'update_post_term_cache' => false,
				'update_post_meta_cache' => false,
				'suppress_filters' => true // phpcs:ignore WordPressVIPMinimum.VIP.WPQueryParams.suppressFiltersTrue -- Okay for CLI.
			] );

			while ( $query->have_posts() ) {
				$query->the_post();

				$post = get_post();
				$content = $post->post_content;

				foreach ( $filters as $filter ) {
					$content = call_user_func( $filter, $content );
				}

				if ( $content !== $post->post_content ) {
					if ( $dry_run ) {
						WP_CLI::log( sprintf( 'Post ID: %d would have the content updated to: %s', $post->ID, $content ) );
					} elseif ( $this->update_content( $post, $content ) ) {
						WP_CLI::log( sprintf( 'Post ID: %d updated.', $post->ID ) );
					} else {
						WP_CLI::log( sprintf( 'Post ID: %d failed to update.', $post->ID ) );
					}
				}

				// Clean-up other fields of a post.
				do_action( 'ione3-content-clean-cli-post', $post, $dry_run );
			}

			WP_CLI::log( 'Preparing next batch' );
			sleep( 1 );
			$this->stop_the_insanity();
			$paged++;

		} while ( $query->post_count );

		WP_CLI::success( 'Complete' );
		$this->end_bulk_operation();
	}

	/**
	 * @param WP_Post $post    Post object.
	 * @param string  $content New content.
	 *
	 * @return bool True on success
	 */
	private function update_content( $post, $content ) {
		$update = [
			'ID' => $post->ID,
			'post_content' => $content,
		];

		return ( wp_update_post( $update ) === $post->ID );
	}

	/**
	 * Remove any out of date media.
	 *
	 * @param WP_Post $post    Post that may have attachments that are out of date.
	 * @param boolean $dry_run Whether to really delete or not.
	 */
	public function remove_attachments( $post, $dry_run ) {
		$class_media_playlist = ione_singleton( 'iOne_Media_Playlist' );

		// If this is a playlist item that is no longer available, delete it.
		if ( in_array( $post->post_type, $class_media_playlist->item_post_types, true ) ) {
			$image_src = get_post_meta( $post->ID, $class_media_playlist->src_meta_key, true );

			if ( ! $this->image_available( $image_src ) ) {
				if ( $dry_run ) {
					WP_CLI::log( sprintf( 'Playlist item: %d with media %s would have been removed.', $post->ID, $image_src ) );
				} elseif ( $this->delete_post_with_attachments( $post->ID ) ) {
					WP_CLI::log( sprintf( 'Playlist item: %d with media %s removed.', $post->ID, $image_src ) );
				} else {
					WP_CLI::log( sprintf( 'Playlist item: %d with media %s failed to remove.', $post->ID, $image_src ) );
				}
			}
		}

		// If this is a playlist, clean up the items.
		if ( $class_media_playlist->post_type === $post->post_type ) {
			$items = $class_media_playlist->playlist_items( $post->ID );

			$filtered_items = [];
			foreach ( $items as $item ) {
				if ( isset( $item['src'] ) && $this->image_available( $item['src'] ) ) {
					$filtered_items[] = $item;
				}
			}

			if ( empty( $filtered_items ) && '2014' > $post->post_date ) {
				if ( $dry_run ) {
					WP_CLI::log( sprintf( 'Playlist: %d with items %s would have been removed.', $post->ID, wp_json_encode( $items ) ) );
				} elseif ( $this->four_ten_playlist( $post->ID ) ) {
					WP_CLI::log( sprintf( 'Playlist: %d removed.', $post->ID ) );
				} else {
					WP_CLI::log( sprintf( 'Playlist: %d failed to remove.', $post->ID ) );
				}
			} elseif ( $filtered_items !== $items ) {
				if ( $dry_run ) {
					WP_CLI::log( sprintf( 'Playlist: %d would have all items except %s removed.', $post->ID, wp_json_encode( $filtered_items ) ) );
				} elseif ( update_post_meta( $post->ID, 'playlist_items', $filtered_items ) ) {
					WP_CLI::log( sprintf( 'Playlist: %d has all items except %s removed.', $post->ID, wp_json_encode( $filtered_items ) ) );
				} else {
					WP_CLI::log( sprintf( 'Playlist: %d failed to update.', $post->ID ) );
				}
			}
		}

		// If featured image is not available, remove it.
		$image_src = wp_get_attachment_url( get_post_thumbnail_id( $post->ID ) );

		if ( ! $this->image_available( $image_src ) ) {
			if ( $dry_run ) {
				WP_CLI::log( sprintf( 'Thumbnail: %s would have been removed from post %d.', $image_src, $post->ID ) );
			} elseif ( delete_post_thumbnail( $post->ID ) ) {
				WP_CLI::log( sprintf( 'Thumbnail: %s removed from post %d.', $image_src, $post->ID ) );
			} else {
				WP_CLI::log( sprintf( 'Thumbnail: %s failed to remove from post %d.', $image_src, $post->ID ) );
			}
		}
	}

	/**
	 * Images are available unless the ione3_helper_image swaps it for the image named ImageUnavailable.
	 *
	 * @param string $image_src Url of image.
	 *
	 * @return bool
	 */
	private function image_available( $image_src ) {
		$check = apply_filters( 'ione3_helper_image', $image_src );

		return ( false === strpos( $check, 'ImageUnavailable.' ) );
	}

	/**
	 * Delete a post and all of its attachments.
	 *
	 * @param integer $post_id      Post to remove permanently.
	 * @param bool    $force_delete Permanently delete or just send to trash.
	 *
	 * @return false|WP_Post|null
	 */
	private function delete_post_with_attachments( $post_id, $force_delete = true ) {
		$attachments = get_attached_media( '', $post_id );
		foreach ( $attachments as $attachment ) {
			WP_CLI::log( sprintf( 'Image: %s removed from post id: %d', wp_get_attachment_url( $attachment->ID ) , $post_id ) );
			wp_delete_attachment( $attachment->ID, $force_delete );
		}

		return wp_delete_post( $post_id, $force_delete );
	}

	/**
	 * Mark a playlist as 410 removed permanently.
	 *
	 * Doesn't delete from db but reports to search engines that it has been permanently removed.
	 *
	 * @param integer $playlist_id  Playlist to remove permanently.
	 *
	 * @return false|WP_Post|null
	 */
	private function four_ten_playlist( $playlist_id ) {
		$class_four_ten = new IOne3_Image_Four_Ten();

		return update_post_meta( $playlist_id, $class_four_ten::POST_META, $class_four_ten::UNAVAILABLE );
	}

	/**
	 * Check if the current request is a dry run.
	 *
	 * @param  array  $args Arguments passed to a command.
	 * @param  string $ref  Dry-run argument key.
	 *
	 * @return boolean
	 */
	protected function is_dry_run( $args, $ref = 'dry-run' ) {
		if ( isset( $args[ $ref ] ) && 'false' === $args[ $ref ] ) {
			return false;
		}

		return true;
	}
}

WP_CLI::add_command( 'ione-content-cleanup', 'IOneContentClean' );