<?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, '&#8230;' );
$excerpt = wp_html_excerpt( $excerpt, 252, '&#8230;' );

$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 );
}