import-from-mastodon.php

<?php

// Prevent direct access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

add_filter( 'import_from_mastodon_post_content', function( $content, $status ) {
	// The plugin, by default, leaves hyperlinks in. This removes them.
	return wp_kses(
		$content,
		array(
			'br' => array(),
			'p'  => array(),
		)
	);
}, 10, 2 );

add_action( 'import_from_mastodon_after_attachments', function( $post_id, $status ) {
	// Unset post thumbnail.
	delete_post_thumbnail( $post_id );

	// Get all uploaded images.
	$attachments = get_attached_media( 'image', $post_id );

	if ( ! empty( $attachments ) ) {
		$post    = get_post( $post_id );
		$content = $post->post_content;

		// Update post content. Classic editor only!
		foreach ( $attachments as $attachment ) {
			$content .= "\n\n" . wp_get_attachment_image( $attachment->ID, 'large' );
		}

		wp_update_post( wp_slash( array(
			'ID'           => $post_id,
			'post_content' => $content,
		) ) );
	}
}, 10, 2 );