<?
/* The Poplink class tracks click pings, a new browser capability proposed for HTML
   by the WHAT Working Group that is currently being tested in development builds
   of Mozilla Firefox.

   A click ping is a request sent by a browser to a web server that tracks a click
   on an outgoing link. A new (and unofficial) *ping* attribute to the HTML *a* tag
   identifies one or more URLs that should be pinged when a link is clicked:

   <a href="http://ekzemplo.com" ping="http://cadenhead.org/pingtrack.php?url=http://ekzemplo.com">Ekzemplo</a>

   In the preceding example, because the Ekzemplo link has a *ping* attribute, a
   browser that supports click pings will request this ping link after loading the
   linked page:
   
   http://cadenhead.org/pingtrack.php?url=http://ekzemplo.com

   Click tracking is common on web sites, implemented through browser redirects that
   interpose a script between the original page and the linked page. The click ping
   adds support for this process to HTML.

   Here's a short example of how it could be used in a PHP script:
   
   // load this file
   require('poplink.php');
   // create a Poplink object
   $pop = new Poplink(); 
   // get an array containing data for the 100 most clicked links
   $popular = $pop->get_popular_links(100); 
   
   Version: 0.1
   Web: http://workbench.cadenhead.org/poplink
   
   Copyright (C) 2006 Rogers Cadenhead

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */

class Poplink_Core {
    /* Sample poplink.php settings: 
    
    // the machine hosting the MySQL server
    var $database_server = "localhost";
    // the MySQL database
    var $database_name = "poplink";
    // the MySQL user with access to the database
    var $database_user = "zeppo";
    // the MySQL user password
    var $database_password = "swordfish"; */
    
    // EDIT VARIABLES BELOW THIS LINE AT YOUR OWN RISK
    var $software_version = "0.1";
    var $last_error = "";
    var $debug = false;
    var $DEBUG_ONLY = true;

    // set up a Poplink object
    function Poplink() {
        // no constructor setup necessary
    }

    // report errors
    function report_error($message, $debug_only = false) {
        if (($debug_only) & (!$this->debug)) return;
        error_log("Poplink: " . $message);
    }
    
    // retrieve last error message
    function get_last_error() {
        return $this->last_error;
    }
    
    // connect to the MySQL database
    function connect_to_database() {
        $db = mysql_connect($this->database_server, $this->database_user,
            $this->database_password);
        if (!$db) {
            $this->report_error("Could not connect to database.");
            return false;
        } else {
            mysql_select_db($this->database_name);
            return true;
        }
    }
    
    // lock database
    function lock_table($read_only = false) {
        $query = "LOCK TABLES $this->database_name WRITE";
        if ($read_only) {
            $query = "LOCK TABLES $this->database_name READ";
        }
        $result = mysql_query($query);
    }
    
    // unlock database
    function unlock_table() {
        $query = "UNLOCK TABLES";
        $result = mysql_query($query);
    }

    // create tables
    function create_database_tables() {
        $output = "";
        if (!$this->connect_to_database()) return;
        $poplink_query = "CREATE TABLE poplink(" .
            "dex MEDIUMINT UNSIGNED AUTO_INCREMENT PRIMARY KEY," .
            "link TINYTEXT," .
            "visits MEDIUMINT UNSIGNED DEFAULT 0," .
            "status SET('allowed', 'banned') DEFAULT 'allowed'" .
            ")";
        $output .= "<p>Attempting to create poplink database ... ";
        $result = mysql_query($poplink_query);
        if ($result == false) {
            $output .= "failed";
        } else {
            $output .= "done";
        }
        return $output;
    }
    
    // retrieve data for a pinged link, creating a new record if necessary
    function get_link($url) {
        if ($url == "") return false;
        $url = $this->get_query_safe_text($url);
        if (!$this->connect_to_database()) return false;
        $query = "SELECT * FROM poplink WHERE link = '$url'";
        $result = mysql_query($query);
        if ($result == false) {
            $this->report_error(mysql_error() . ": $query");
            return false;
        }
        if (mysql_num_rows($result) < 1) {
            // add a new link
            if ($this->add_link($url) === true) {
                $this->get_link($url);
            }
        } else {
            // retrieve the link
            $url_data = mysql_fetch_array($result);
            $url_data['visits'] = $url_data['visits'] + 1;
            $url_data['link'] = $this->get_slash_decoded_text($url_data['link']);
            $query = "UPDATE poplink SET visits = {$url_data['visits']} WHERE link = '$url'";
            $result = mysql_query($query);
            if ($result == false) {
                $this->report_error(mysql_error() . ": $query");
                return false;
            }
            return $url_data;   
        }
    }
    
    // add a new link to the database
    function add_link($url) {
        if ($url == "") return false;
        $url = $this->get_query_safe_text($url);
        if (!$this->connect_to_database()) return false;
        $link = $url;
        $visits = 0;
        $status = 'allowed';
        $query = "INSERT INTO poplink VALUES(0, '$link', '$visits', '$status')";
        $result = mysql_query($query);
        if ($result == false) {
            $this->report_error(mysql_error() . ": $query");
            return false;
        }
        return true;
    }
    
    // get an array containing the most clicked links
    function get_popular_links($limit = 100) {
        $query = "SELECT * FROM poplink ORDER BY visits DESC LIMIT $limit";
        if (!$this->connect_to_database()) return;
        $result = mysql_query($query);
        if ($result == false) {
            $this->report_error(mysql_error() . ": $query");
            // create database if it doesn't exist yet
            $this->create_database_tables();
            return false;
        }
        $links = array();
        $count = 0;
        while ($row = mysql_fetch_array($result)) {
            $links[$count] = $row;
            $count++;
        }
        return $links;
    }
           
    // the functions after this point are used within the class and should not be called externally
    
    // make text safe for MySQL database query
    function get_query_safe_text($text) {
        $text = $this->get_slash_decoded_text($text);
        $text = mysql_real_escape_string($text);
        return $text;
    }

    // strip slashes from database text if necessary
    function get_slash_decoded_text($text) {
        if (get_magic_quotes_gpc()) {
            $text = stripslashes($text);
        }
        return $text;
   }
    
    // add slashes to database text if necessary
    function get_slash_encoded_text($text) {
        if (!get_magic_quotes_gpc()) {
            return addslashes($text);
        } else {
            return $text;
        }
    }
}