<?php
/*
Plugin Name: Ajax Scroll
Description: Turns standard next and previous post links into animated AJAX scrolling.
Author: Nicholas Crawford
Version: 0.4
Author URI: http://www.bankofcanada.ca/
Plugin URI: http://bankofcanada.wordpress.com/
*/

/*
         _._._                       _._._
        _|   |_                     _|   |_
        | ... |_._._._._._._._._._._| ... |
        | ||| |  o BANK OF CANADAo  | ||| |
        | """ |  """    """    """  | """ |
   ())  |[-|-]| [-|-]  [-|-]  [-|-] |[-|-]|  ())
  (())) |     |---------------------|     | (()))
 (())())| """ |  """    """    """  | """ |(())())
 (()))()|[-|-]|  :::   .-"-.   :::  |[-|-]|(()))()
 ()))(()|     | |~|~|  |_|_|  |~|~| |     |()))(()
    ||  |_____|_|_|_|__|_|_|__|_|_|_|_____|  ||
 ~ ~^^ @@@@@@@@@@@@@@/=======\@@@@@@@@@@@@@@ ^^~ ~
      ^~^~                                ~^~^

Should we force the user to specify the ID?  If we use this, it has a default.
But that means if they foget to specify the ID on a certain theme page, the link won't work.

global $as_elem_id;
if (empty($as_elem_id))
	$as_elem_id = 'content';
*/


// if calling the file directly, we are looking to load a URL via AJAX
if ( str_replace('\\', '/', __FILE__) == $_SERVER['SCRIPT_FILENAME'] )
{
	require_once('../../../wp-load.php');

	AjaxScroll::ajax_call();
}
else
{
	//add_action('wp_ajax_ajax_scroll', array('AjaxScroll', 'ajax_call'));
	//add_action('wp_ajax_nopriv_ajax_scroll', array('AjaxScroll', 'ajax_call'));
	add_action('get_pagenum_link', array('AjaxScroll', 'replace_link'), 10000); // should be called as the very last action
	add_action('clean_url', array('AjaxScroll', 'fix_link'), 10000); // should be called as the very last action

	wp_enqueue_script('jquery-ui-slide', plugins_url('ajax-scroll/js/jquery-ui-1.7.2.effects.slide.min.js'), array('jquery'));
	wp_enqueue_script('ajax-scroll', plugins_url('ajax-scroll/js/ajax-scroll-js.php'), array('jquery', 'jquery-ui-slide'));
	wp_localize_script('ajax-scroll', 'wp_ajax_scroll', array(
			'ajax_url' => get_bloginfo( 'wpurl' ).'/wp-content/plugins/ajax-scroll/ajax-scroll.php' //'/wp-admin/admin-ajax.php'
			));
}

class AjaxScroll
{
	public function replace_link($link)
	{
		global $as_elem_id;
		if ( empty($as_elem_id) )
			return $link;
	
		// link url
		$query = parse_str( parse_url ($link, PHP_URL_QUERY) );
		if ( isset($query['p']) && is_numeric($query['p']) )
		{
			$page = $query['p'];
		}
		else
		{
			$check_link = rtrim(parse_url ($link, PHP_URL_PATH), '/');
			$method1 = substr($check_link, strrpos($check_link, '/') + 1);
			if ( is_numeric($method1) )
				$page = $method1;
			else
				$page = 1;
		}

		// current url
		$current_url = 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
		$current_query = parse_str( parse_url ( $current_url, PHP_URL_QUERY ) );

		if ( isset($current_query['p']) && is_numeric($current_query['p']) )
		{
			$current_page = $current_query['p'];
		}
		else
		{
			$check_link = rtrim(parse_url ($current_url, PHP_URL_PATH), '/');
			$current_method1 = substr($check_link, strrpos($check_link, '/') + 1);
			if ( is_numeric($current_method1) )
				$current_page = $current_method1;
			else
				$current_page = 1;
		}

		if ( $current_page < $page )
			$direction = 'older';
		else
			$direction = 'newer';
			
		return 'http://ajax-scroll175926233/javascript:ajax_scroll(\'' . $direction . '\', \'' . urlencode($link) . '\', \'' . $as_elem_id . '\');';
	}
	
	public function fix_link($link)
	{
		if ( substr($link, 0, 39) == 'http://ajax-scroll175926233/javascript:' )
			return substr_replace($link, '', 0, 28);
		return $link;
	}
	
	public static function ajax_call()
	{
		$findID = $_POST['as_container'];
		if ( empty($findID) )
		{
			global $as_elem_id;
			$findID = $as_elem_id;
		}
	
		$children = @DOMDocument::loadHTML(wp_remote_fopen($_POST['as_url']))->getElementById($findID)->childNodes;
		
		if (empty($children))
			exit('Unable to locate element ID "'.$findID.'" in file "'.$_POST['as_url'].'"');

		foreach ($children as $child)
		{
		    $tmp_doc = new DOMDocument();
		    $tmp_doc->appendChild($tmp_doc->importNode($child,true));       
		    $innerHTML .= trim($tmp_doc->saveHTML());
		} 
		
		header('Content-Type: text/html; charset=utf-8');
		echo $innerHTML;
		exit;
	}
	
	/* 
	 *	$url 		- URI to pull contents from
	 * $direction	- "newer" or "older"
	 * $text		- text to link
	 * $container	- id of the element that will be transitioned
	 */
	static public function generateLink($url, $direction, $text, $container='')
	{
		if ( empty($container) )
		{
			global $as_elem_id;
			$container = $as_elem_id;
		}
		echo '<a href="" onclick="', get_generateLink($url, $direction, $container), 'return false;" title="', htmlspecialchars($text, ENT_COMPAT, 'UTF-8', false), '">', $text, '</a>';
	}
	
	static public function get_generateLink($url, $direction, $container='')
	{
		if ( empty($container) )
		{
			global $as_elem_id;
			$container = $as_elem_id;
		}
		return 'ajax_scroll(\'' . $direction . '\', \'' . urlencode($url) . '\', \'' . $container . '\');';
	}
}