activitypub-limit-unnecessary-updates.php

<?php

add_action( 'transition_post_status', function ( $new_status, $old_status, $post ) { // phpcs:ignore PEAR.Functions.FunctionCallSignature.ContentAfterOpenBracket,PEAR.Functions.FunctionCallSignature.MultipleArguments
	if ( 'publish' !== $new_status || 'publish' !== $old_status ) {
		// Run only on when the post is public, or was public.
		return;
	}

	// $hash = get_transient( "activitypub:sent:post:{$post->ID}" );
	$hash = get_post_meta( $post->ID, '_activitypub_sent_hash', true );

	if ( '' === $hash ) {
		// Looks like this post's new. Do not interrupt the normal flow of things.
		error_log( "[AP/Limit Updates] The post with ID {$post->ID} hasn't yet been sent out." );
		return;
	}

	// "Clone" `$post`, keeping only the following properties.
	$obj = array_filter(
		(array) $post,
		function ( $key ) {
			return in_array( $key, array( 'post_name', 'post_title', 'post_content', 'post_type', 'post_author' ), true );
		},
		ARRAY_FILTER_USE_KEY
	);

	$cats = wp_get_post_categories( $post->ID, array( 'fields' => 'names' ) );
	$tags = wp_get_post_tags( $post->ID, array( 'fields' => 'names' ) );

	// Because I use Gutenberg in combination with "old style" meta boxes (added
	// by different plugins), there'll be two requests to WP's back end, and two
	// calls to `transition_post_status`. The first will still show the old tags,
	// the second one will show the newer tags.
	// error_log( serialize( $cats ) . serialize( $tags ) );

	// Either way, this works. Mostly.
	if ( md5( serialize( $obj ) . serialize( $cats ) . serialize( $tags ) ) === $hash && class_exists( '\\Activitypub\\Scheduler' ) && method_exists( \Activitypub\Scheduler::class, 'schedule_post_activity' ) ) {
		// We're updating a post, but it hasn't actually changed. Unhook scheduler.
		error_log( "[AP/Limit Updates] Post hasn't actually changed. Unscheduling federation for the post with ID {$post->ID}." );
		remove_action( 'transition_post_status', array( \Activitypub\Scheduler::class, 'schedule_post_activity' ), 33 );
	}
}, 30, 3 ); // phpcs:ignore PEAR.Functions.FunctionCallSignature.CloseBracketLine,PEAR.Functions.FunctionCallSignature.MultipleArguments

add_action( 'activitypub_safe_remote_post_response', function ( $response, $url, $body ) { // phpcs:ignore PEAR.Functions.FunctionCallSignature.ContentAfterOpenBracket,PEAR.Functions.FunctionCallSignature.MultipleArguments
	if ( is_wp_error( $response ) ) {
		// Reschedule?
		return;
	}

	// It'd be better to do this once per scheduled event rather than after every POST! But I'm not sure there's a hook for that.
	$array = json_decode( $body, true );

	if ( empty( $array['object']['id'] ) || ! filter_var( $array['object']['id'], FILTER_VALIDATE_URL ) ) {
		return;
	}

	$fragment = wp_parse_url( $array['object']['id'], PHP_URL_FRAGMENT );

	if ( ! empty( $fragment ) && preg_match( '~^comment-\d+$~', $fragment ) ) {
		// Comment. We don't support these, yet.
		return;
	}

	$post = get_post( url_to_postid( $array['object']['id'] ) );

	if ( empty( $post->ID ) ) {
		return;
	}

	// "Clone" `$post`, keeping only the following properties.
	$obj = array_filter(
		(array) $post,
		function ( $key ) {
			return in_array( $key, array( 'post_name', 'post_title', 'post_content', 'post_type', 'post_author' ), true );
		},
		ARRAY_FILTER_USE_KEY
	);

	$cats = wp_get_post_categories( $post->ID, array( 'fields' => 'names' ) );
	$tags = wp_get_post_tags( $post->ID, array( 'fields' => 'names' ) );

	// Generate a hash of the "post array," categories, and tags.
	$hash = md5( serialize( $obj ) . serialize( $cats ) . serialize( $tags ) );

	// set_transient( "activitypub:sent:post:{$post->ID}", $hash, MONTH_IN_SECONDS );
	error_log( "[AP/Limit Updates] Saving the hash for the post with ID {$post->ID}." );
	update_post_meta( $post->ID, '_activitypub_sent_hash', $hash );
}, 10, 3 ); // phpcs:ignore PEAR.Functions.FunctionCallSignature.CloseBracketLine,PEAR.Functions.FunctionCallSignature.MultipleArguments

To do: check out activitypub_send_activity_to_followers and the "state" instead.