PrivatePostAccess.php

<?php 
/**
 * Plugin Name: Private Post Access
 * Plugin URI: http://wordpress.stackexchange.com/questions/130967/get-full-page-html-for-a-non-public-wordpress-page
 * Description: Generate and handle urls that allow access to posts in non-public status.
 * Author: G. M.
 * Author URI: http://wordpress.stackexchange.com/users/35541/g-m
 * 
 */
 
/**
 * HOW TO USE
 *
 * First of all
 *  - install this file as a plugin and activate
 *  - OR just include this file in theme functions.php or in another plugin.
 * 
 * After that, the url to use to show the post even if in private state should be get using:
 *
 * PrivatePostAccess::url( $post ); instead of get_permalink( $post );
 *
 * The variable $post can be a post id or a post object.
 *
 * Sending a request using that url will show the post even if in a not public state, e.g. draft or pending.
 * that url can also be used to retrieve a post html using HTTP API or raw cUrl
 *
 * Example:
 *
 *
 * 		$url = PrivatePostAccess::url( 605 ); // 605 is the post ID
 *
 * 		if ( filter_var( $url, FILTER_VALIDATE_URL ) ) {
 * 			$response = wp_remote_get( $url );
 * 			$post_full_body = $response ? wp_remote_retrieve_body( $response ) : FALSE;
 * 		}	 
 *  
 */
 
class PrivatePostAccess {
	
	// change this string to whatever you want
	const SECRET  = 'ASlajADFA71scfas57dFsdtfgasd897Vsd';
	
	private static $hooksdone = array();
	
	private $requested_status;
	
	private $requested_was_public = TRUE;
	
	
	/**
	 * Get the url of a post that will allow to get post even if it has a not public status
	 *
	 * @param mixed $post post id, post object or null (inside the loop)
	 * @return string post url
	 * @access public
	 */
	static function url( $post = NULL ) {
		if ( empty($post) ) global $post;
		if ( is_numeric($post) ) $post = get_post( $post );
		if ( ! $post instanceof WP_Post ) return FALSE;
		if ( self::isPublic($post) ) return get_permalink($post);
		$nonce = wp_create_nonce( __CLASS__ );
		$vars = array('nonce' => $nonce, 'key' => self::SECRET );
		return add_query_arg( $vars, get_permalink($post) );
	}
	
	
	/**
	 * Check if the status of a post is public or not
	 *
	 * @param WP_Post $post post object
	 * @return bool true if post status is public, false otherwise
	 * @access protected
	 */
	protected static function isPublic( WP_Post $post = NULL ) {
		if ( $post instanceof WP_Post ) {
			$status = get_post_status( $post );
			$post_status_obj = get_post_status_object( $status );
			return $post_status_obj->public;
		}
	}
	
	
	/**
	 * Init the plugin
	 *
	 * @return null
	 * @access public
	 */
	function init() {
		add_action('pre_get_posts', array($this, 'hooks') );
	}
	
	
	/**
	 * Add the hook needed to allow not public post to be visible
	 *
	 * @param WP_Query $query current main query
	 * @return null
	 * @access public
	 */
	function hooks( WP_Query $query ) {
		if ( current_filter() !== 'pre_get_posts' || isset( self::$hooksdone[current_filter()] ) ) return;
		self::$hooksdone[current_filter()] = 1;
		if ( ! is_admin() && $query->is_main_query() && is_singular() ) {
			add_filter('posts_results', array($this, 'enable') );
			add_filter('the_posts', array($this, 'enable') );
		}
	}
	
	
	/**
	 * Run on two hooks, 'posts_results' and 'the_posts'
	 * on first fake global $wp_post_statuses to make current post status appear public,
	 * on second restore the status
	 *
	 * @param WP_Post $results the current queried post
	 * @return WP_Post
	 * @access public
	 */
	function enable( $results ) {
		if ( isset( self::$hooksdone[current_filter()] ) ) return $results; 
		self::$hooksdone[current_filter()] = 1;
		if ( ! is_admin() && $this->checkRequest() ) {
			global $wp_post_statuses;
			if ( current_filter() === 'posts_results' && ! $this->isPublic($results[0]) ) {
				$this->requested_status = get_post_status( $results[0] );
				$this->requested_was_public = FALSE;
				$wp_post_statuses[$this->requested_status]->public = TRUE;
			} elseif ( ( current_filter() === 'the_posts' ) && ! $this->requested_was_public ) {
				$wp_post_statuses[$this->requested_status]->public = FALSE;
			}
		}	
		return $results;
	}
	
	
	/**
	 * Check the request to verify query vars
	 *
	 * @return null|bool
	 * @access protected
	 */
	protected function checkRequest() {
		static $good;
		if ( is_null($good) ) {
			$good = $this->checkNonce() && $this->checkSecret();
		}
		return $good;
	}
	
	/**
	 * Check the request to verify nonce
	 *
	 * @return bool
	 * @access protected
	 */
	protected function checkNonce() {
		$nonce = filter_input( INPUT_GET, 'nonce', FILTER_SANITIZE_STRING );
		return ( ! empty($nonce) && wp_verify_nonce($nonce, __CLASS__) );
	}
	
	
	/**
	 * Check the request to verify nonce
	 *
	 * @return bool
	 * @access protected
	 */
	protected function checkSecret() {
		$key = filter_input( INPUT_GET, 'key', FILTER_SANITIZE_STRING );
		return ( ! empty($key) && $key === self::SECRET );
	}
}


add_action( 'init', array( new PrivatePostAccess, 'init' ) );