<?php

/**

 * Handle Trackbacks and Pingbacks Sent to WordPress

 *

 * @since 0.71

 *

 * @package WordPress

 * @subpackage Trackbacks

 */

if ( empty( $wp ) ) {

	require_once __DIR__ . '/wp-load.php';

	wp( array( 'tb' => '1' ) );

}

// Always run as an unauthenticated user.

wp_set_current_user( 0 );

/**

 * Response to a trackback.

 *

 * Responds with an error or success XML message.

 *

 * @since 0.71

 *

 * @param int|bool $error         Whether there was an error.

 *                                Default '0'. Accepts '0' or '1', true or false.

 * @param string   $error_message Error message if an error occurred. Default empty string.

 */

function trackback_response( $error = 0, $error_message = '' ) {

	header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ) );

	if ( $error ) {

		echo '<?xml version="1.0" encoding="utf-8"?' . ">\n";

		echo "<response>\n";

		echo "<error>1</error>\n";

		echo "<message>$error_message</message>\n";

		echo '</response>';

		die();

	} else {

		echo '<?xml version="1.0" encoding="utf-8"?' . ">\n";

		echo "<response>\n";

		echo "<error>0</error>\n";

		echo '</response>';

	}

}

if ( ! isset( $_GET['tb_id'] ) || ! $_GET['tb_id'] ) {

	$post_id = explode( '/', $_SERVER['REQUEST_URI'] );

	$post_id = (int) $post_id[ count( $post_id ) - 1 ];

}

$trackback_url = isset( $_POST['url'] ) ? $_POST['url'] : '';

$charset       = isset( $_POST['charset'] ) ? $_POST['charset'] : '';

// These three are stripslashed here so they can be properly escaped after mb_convert_encoding().

$title     = isset( $_POST['title'] ) ? wp_unslash( $_POST['title'] ) : '';

$excerpt   = isset( $_POST['excerpt'] ) ? wp_unslash( $_POST['excerpt'] ) : '';

$blog_name = isset( $_POST['blog_name'] ) ? wp_unslash( $_POST['blog_name'] ) : '';

if ( $charset ) {

	$charset = str_replace( array( ',', ' ' ), '', strtoupper( trim( $charset ) ) );

	// Validate the specified "sender" charset is available on the receiving site.

	if ( function_exists( 'mb_list_encodings' ) && ! in_array( $charset, mb_list_encodings(), true ) ) {

		$charset = '';

	}

}

if ( ! $charset ) {

	$charset = 'ASCII, UTF-8, ISO-8859-1, JIS, EUC-JP, SJIS';

}

// No valid uses for UTF-7.

if ( str_contains( $charset, 'UTF-7' ) ) {

	die;

}

// For international trackbacks.

if ( function_exists( 'mb_convert_encoding' ) ) {

	$title     = mb_convert_encoding( $title, get_option( 'blog_charset' ), $charset );

	$excerpt   = mb_convert_encoding( $excerpt, get_option( 'blog_charset' ), $charset );

	$blog_name = mb_convert_encoding( $blog_name, get_option( 'blog_charset' ), $charset );

}

// Escape values to use in the trackback.

$title     = wp_slash( $title );

$excerpt   = wp_slash( $excerpt );

$blog_name = wp_slash( $blog_name );

if ( is_single() || is_page() ) {

	$post_id = $posts[0]->ID;

}

if ( ! isset( $post_id ) || ! (int) $post_id ) {

	trackback_response( 1, __( 'I really need an ID for this to work.' ) );

}

if ( empty( $title ) && empty( $trackback_url ) && empty( $blog_name ) ) {

	// If it doesn't look like a trackback at all.

	wp_redirect( get_permalink( $post_id ) );

	exit;

}

if ( ! empty( $trackback_url ) && ! empty( $title ) ) {

	/**

	 * Fires before the trackback is added to a post.

	 *

	 * @since 4.7.0

	 *

	 * @param int    $post_id       Post ID related to the trackback.

	 * @param string $trackback_url Trackback URL.

	 * @param string $charset       Character set.

	 * @param string $title         Trackback title.

	 * @param string $excerpt       Trackback excerpt.

	 * @param string $blog_name     Site name.

	 */

	do_action( 'pre_trackback_post', $post_id, $trackback_url, $charset, $title, $excerpt, $blog_name );

	header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ) );

	if ( ! pings_open( $post_id ) ) {

		trackback_response( 1, __( 'Sorry, trackbacks are closed for this item.' ) );

	}

	$title   = wp_html_excerpt( $title, 250, '…' );

	$excerpt = wp_html_excerpt( $excerpt, 252, '…' );

	$comment_post_id      = (int) $post_id;

	$comment_author       = $blog_name;

	$comment_author_email = '';

	$comment_author_url   = $trackback_url;

	$comment_content      = "<strong>$title</strong>\n\n$excerpt";

	$comment_type         = 'trackback';

	$dupe = $wpdb->get_results(

		$wpdb->prepare(

			"SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_author_url = %s",

			$comment_post_id,

			$comment_author_url

		)

	);

	if ( $dupe ) {

		trackback_response( 1, __( 'There is already a ping from that URL for this post.' ) );

	}

	$commentdata = array(

		'comment_post_ID' => $comment_post_id,

	);

	$commentdata += compact(

		'comment_author',

		'comment_author_email',

		'comment_author_url',

		'comment_content',

		'comment_type'

	);

	$result = wp_new_comment( $commentdata );

	if ( is_wp_error( $result ) ) {

		trackback_response( 1, $result->get_error_message() );

	}

	$trackback_id = $wpdb->insert_id;

	/**

	 * Fires after a trackback is added to a post.

	 *

	 * @since 1.2.0

	 *

	 * @param int $trackback_id Trackback ID.

	 */

	do_action( 'trackback_post', $trackback_id );

	trackback_response( 0 );

}