<?php
/*
Plugin Name: ambdownload
Plugin URI: http://blog.alex.org.uk/
Description: Redirect a given page to a download URL
Version: 2.2
Author: Alex Bligh
Author URI: http://blog.alex.org.uk
*/

class ambdownload
{
	function getDownloadLink($user, $file="default")
	{
	 	$time = time();
	        $secret = rtrim(file_get_contents("/etc/apache2/download.secret"));
		$id = $user;
		$hash = hash("sha256",$time.":".$id.":".$file.":".$secret);
		$link = "http://server.example.com/download?";
		return $link.sprintf("id=%s&file=%s&time=%s&hash=%s",urlencode($id),urlencode($file),$time,$hash);
	}

	function downloadRedirect()
	{	
	  	global $post;
		if ((is_single() || is_singular() || is_page()))
	   	{
			$download_file = get_post_meta($post->ID, 'download_file', true);  
			if ($download_file) {  
				global $current_user;
				get_currentuserinfo();
				wp_redirect(ambdownload::getDownloadLink($current_user->user_email, $download_file));
				exit;
			}
		}
	}
}


add_action( 'template_redirect', array('ambdownload', 'downloadRedirect'), 1, 2);