<?php
/**
 * HTTPS detection functions.
 *
 * @package WordPress
 * @since 5.7.0
 */

/**
 * Checks whether the website is using HTTPS.
 *
 * This is based on whether both the home and site URL are using HTTPS.
 *
 * @since 5.7.0
 * @see wp_is_home_url_using_https()
 * @see wp_is_site_url_using_https()
 *
 * @return bool True if using HTTPS, false otherwise.
 */
function wp_is_using_https() {
    if ( ! wp_is_home_url_using_https() ) {
        return false;
    }

    return wp_is_site_url_using_https();
}

/**
 * Checks whether the current site URL is using HTTPS.
 *
 * @since 5.7.0
 * @see home_url()
 *
 * @return bool True if using HTTPS, false otherwise.
 */
function wp_is_home_url_using_https() {
    return 'https' === wp_parse_url( home_url(), PHP_URL_SCHEME );
}

/**
 * Checks whether the current site's URL where WordPress is stored is using HTTPS.
 *
 * This checks the URL where WordPress application files (e.g. wp-blog-header.php or the wp-admin/ folder)
 * are accessible.
 *
 * @since 5.7.0
 * @see site_url()
 *
 * @return bool True if using HTTPS, false otherwise.
 */
function wp_is_site_url_using_https() {
    /*
     * Use direct option access for 'siteurl' and manually run the 'site_url'
     * filter because `site_url()` will adjust the scheme based on what the
     * current request is using.
     */
    /** This filter is documented in wp-includes/link-template.php */
    $site_url = apply_filters( 'site_url', get_option( 'siteurl' ), '', null, null );

    return 'https' === wp_parse_url( $site_url, PHP_URL_SCHEME );
}

/**
 * Checks whether HTTPS is supported for the server and domain.
 *
 * This function makes an HTTP request through `wp_get_https_detection_errors()`
 * to check for HTTPS support. As this process can be resource-intensive,
 * it should be used cautiously, especially in performance-sensitive environments,
 * to avoid potential latency issues.
 *
 * @since 5.7.0
 *
 * @return bool True if HTTPS is supported, false otherwise.
 */
function wp_is_https_supported() {
    $https_detection_errors = wp_get_https_detection_errors();

    // If there are errors, HTTPS is not supported.
    return empty( $https_detection_errors );
}

/**
 * Runs a remote HTTPS request to detect whether HTTPS supported, and stores potential errors.
 *
 * This function checks for HTTPS support by making an HTTP request. As this process can be resource-intensive,
 * it should be used cautiously, especially in performance-sensitive environments.
 * It is called when HTTPS support needs to be validated.
 *
 * @since 6.4.0
 * @access private
 *
 * @return array An array containing potential detection errors related to HTTPS, or an empty array if no errors are found.
 */
function wp_get_https_detection_errors() {
    /**
     * Short-circuits the process of detecting errors related to HTTPS support.
     *
     * Returning a `WP_Error` from the filter will effectively short-circuit the default logic of trying a remote
     * request to the site over HTTPS, storing the errors array from the returned `WP_Error` instead.
     *
     * @since 6.4.0
     *
     * @param null|WP_Error $pre Error object to short-circuit detection,
     *                           or null to continue with the default behavior.
     */
    $support_errors = apply_filters( 'pre_wp_get_https_detection_errors', null );
    if ( is_wp_error( $support_errors ) ) {
        return $support_errors->errors;
    }

    $support_errors = new WP_Error();

    $response = wp_remote_request(
        home_url( '/', 'https' ),
        array(
            'headers'   => array(
                'Cache-Control' => 'no-cache',
            ),
            'sslverify' => true,
        )
    );

    if ( is_wp_error( $response ) ) {
        $unverified_response = wp_remote_request(
            home_url( '/', 'https' ),
            array(
                'headers'   => array(
                    'Cache-Control' => 'no-cache',
                ),
                'sslverify' => false,
            )
        );

        if ( is_wp_error( $unverified_response ) ) {
            $support_errors->add(
                'https_request_failed',
                __( 'HTTPS request failed.' )
            );
        } else {
            $support_errors->add(
                'ssl_verification_failed',
                __( 'SSL verification failed.' )
            );
        }

        $response = $unverified_response;
    }

    if ( ! is_wp_error( $response ) ) {
        if ( 200 !== wp_remote_retrieve_response_code( $response ) ) {
            $support_errors->add( 'bad_response_code', wp_remote_retrieve_response_message( $response ) );
        } elseif ( false === wp_is_local_html_output( wp_remote_retrieve_body( $response ) ) ) {
            $support_errors->add( 'bad_response_source', __( 'It looks like the response did not come from this site.' ) );
        }
    }

    return $support_errors->errors;
}

/**
 * Checks whether a given HTML string is likely an output from this WordPress site.
 *
 * This function attempts to check for various common WordPress patterns whether they are included in the HTML string.
 * Since any of these actions may be disabled through third-party code, this function may also return null to indicate
 * that it was not possible to determine ownership.
 *
 * @since 5.7.0
 * @access private
 *
 * @param string $html Full HTML output string, e.g. from a HTTP response.
 * @return bool|null True/false for whether HTML was generated by this site, null if unable to determine.
 */
function wp_is_local_html_output( $html ) {
    // 1. Check if HTML includes the site's Really Simple Discovery link.
    if ( has_action( 'wp_head', 'rsd_link' ) ) {
        $pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( site_url( 'xmlrpc.php?rsd', 'rpc' ) ) ); // See rsd_link().
        return str_contains( $html, $pattern );
    }

    // 2. Check if HTML includes the site's REST API link.
    if ( has_action( 'wp_head', 'rest_output_link_wp_head' ) ) {
        // Try both HTTPS and HTTP since the URL depends on context.
        $pattern = preg_replace( '#^https?:(?=//)#', '', esc_url( get_rest_url() ) ); // See rest_output_link_wp_head().
        return str_contains( $html, $pattern );
    }

    // Otherwise the result cannot be determined.
    return null;
}