<?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' ) );
}

/**
* 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.
*/
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>';
}
}

// Trackback is done by a POST.
$request_array = 'HTTP_POST_VARS';

if ( ! isset( $_GET['tb_id'] ) || ! $_GET['tb_id'] ) {
$tb_id = explode( '/', $_SERVER['REQUEST_URI'] );
$tb_id = intval( $tb_id[ count( $tb_id ) - 1 ] );
}

$tb_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 ) ) );
} else {
$charset = 'ASCII, UTF-8, ISO-8859-1, JIS, EUC-JP, SJIS';
}

// No valid uses for UTF-7.
if ( false !== strpos( $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 );
}

// Now that mb_convert_encoding() has been given a swing, we need to escape these three.
$title = wp_slash( $title );
$excerpt = wp_slash( $excerpt );
$blog_name = wp_slash( $blog_name );

if ( is_single() || is_page() ) {
$tb_id = $posts[0]->ID;
}

if ( ! isset( $tb_id ) || ! intval( $tb_id ) ) {
trackback_response( 1, __( 'I really need an ID for this to work.' ) );
}

if ( empty( $title ) && empty( $tb_url ) && empty( $blog_name ) ) {
// If it doesn't look like a trackback at all.
wp_redirect( get_permalink( $tb_id ) );
exit;
}

if ( ! empty( $tb_url ) && ! empty( $title ) ) {
/**
* Fires before the trackback is added to a post.
*
* @since 4.7.0
*
* @param int $tb_id Post ID related to the trackback.
* @param string $tb_url Trackback URL.
* @param string $charset Character Set.
* @param string $title Trackback Title.
* @param string $excerpt Trackback Excerpt.
* @param string $blog_name Blog Name.
*/
do_action( 'pre_trackback_post', $tb_id, $tb_url, $charset, $title, $excerpt, $blog_name );

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

if ( ! pings_open( $tb_id ) ) {
trackback_response( 1, __( 'Sorry, trackbacks are closed for this item.' ) );
}

$title = wp_html_excerpt( $title, 250, '&#8230;' );
$excerpt = wp_html_excerpt( $excerpt, 252, '&#8230;' );

$comment_post_ID = (int) $tb_id;
$comment_author = $blog_name;
$comment_author_email = '';
$comment_author_url = $tb_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, __( 'We already have a ping from that URL for this post.' ) );
}

$commentdata = compact( 'comment_post_ID', '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 );
}