<?php
/*
Plugin Name: Ajax Scroll
Description: Turns standard next and previous post links into animated AJAX scrolling.
Author: Nicholas Crawford
Version: 0.3
Author URI: http://www.bankofcanada.ca/
Plugin URI: http://bankofcanada.wordpress.com/
*/

/*
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';
*/

add_filter('previous_post_link', array('AjaxScroll', 'set_link'));
add_filter('next_post_link', array('AjaxScroll', 'set_link'));
add_action('get_pagenum_link', array('AjaxScroll', 'replace_link'));
add_action('clean_url', array('AjaxScroll', 'fix_link'));
add_action('wp_ajax_ajax_scroll', array('AjaxScroll', 'ajax_call'));
add_action('wp_ajax_nopriv_ajax_scroll', array('AjaxScroll', 'ajax_call'));

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-admin/admin-ajax.php'
			));

class AjaxScroll
{
	public function set_link($link)
	{
		preg_match('/href="(.*?)"/', $link, $match);
		echo str_replace($match[1], AjaxScroll::fix_link(AjaxScroll::replace_link($match[1])), $link);
	}

	public function replace_link($link)
	{
		global $as_elem_id;
		if ( empty($as_elem_id) )
			return $link;
	
		// link url
		parse_str( parse_url ($link, PHP_URL_QUERY), $query );

		if ( isset($query['p']) && is_numeric($query['p']) )
		{
			$page = $query['p'];
		}
		elseif ( isset($query['paged']) && is_numeric($query['paged']) )
		{
			$page = $query['paged'];
		}
		else
		{
			$check_link = str_replace(parse_url (get_bloginfo('wpurl'), PHP_URL_PATH), '', parse_url ($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'];
		parse_str( parse_url ( $current_url, PHP_URL_QUERY ), $current_query );
		
		if ( isset($current_query['p']) && is_numeric($current_query['p']) )
		{
			$current_page = $current_query['p'];
		}
		elseif ( isset($current_query['paged']) && is_numeric($current_query['paged']) )
		{
			$current_page = $current_query['paged'];
		}
		else
		{
			$check_link = str_replace( parse_url (get_bloginfo('wpurl'), PHP_URL_PATH), '', parse_url ($current_url, PHP_URL_PATH));
			$method1 = substr($check_link, strrpos($check_link, '/') + 1);
			if ( is_numeric($method1) )
				$current_page = $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 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());
		} 
		
		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 . '\');';
	}
}