<?php

    $basechars = '23456789abcdefghjkmnpqrstuvwxyz';

    $base = strlen($basechars);

    function my_encode($int) {

        global $base, $basechars;

        $nb = $int;

        $res = '';

        while($nb > 0 or strlen($res) == 0) {

            $mod = $nb % $base;

            $res = $basechars[$mod].$res;

            $nb = ($nb - $mod) / $base;

        }

        return $res;

    }

    function my_decode($str) {

        global $base, $basechars;

        $s = strtolower($str);

        $m = 1;

        $res = 0;

        for ($i = strlen($s)-1; $i >= 0; $i--) {

            $res += $m * strpos($basechars, $s[$i]);

            $m *= $base;

        }

        return $res;

    };

    require('connect.inc.php');

    session_start();

    $data = isset($_REQUEST['data']) ? $_REQUEST['data'] : false;

    $insdata = pg_escape_string($data ? $data : '{}');

    if (isset($_REQUEST['sessionid'])) {

        $_SESSION['sessionid'] = $_REQUEST['sessionid'];

    }

    if (isset($_REQUEST['sessionkey'])) {

        $_SESSION['sessionkey'] = $_REQUEST['sessionkey'];

    }

    if (isset($_SESSION['sessionid'])) {

        $sidnum = my_decode($_SESSION['sessionid']);

        $rq = pg_query("SELECT editkey FROM hdaviz_sessions WHERE id = $sidnum");

        if ($ligne = pg_fetch_row($rq)) {

            if (isset($_SESSION['sessionkey'])) {

                $keynum = my_decode($_SESSION['sessionkey']);

                if ($keynum == $ligne[0]) {

                    $write = true;

                } else {

                    $write = false;

                    unset($_SESSION['sessionkey']);

                }

            } else {

                $keynum = false;

                $write = false;

            }

        } else {

            unset($_SESSION['sessionid']);

        }

    }

    if (!isset($_SESSION['sessionid'])) {

        do {

            $sidnum = mt_rand(1000, 100000000);

            $rq = pg_query("SELECT COUNT(*) FROM hdaviz_sessions WHERE id=$sidnum");

            $l = pg_fetch_row($rq);

            $nb = $l[0];

            pg_free_result($rq);

        } while ($nb > 0);

        $keynum = mt_rand(104, 100000001);

        $rq = pg_query("INSERT INTO hdaviz_sessions (id, editkey, data) VALUES ($sidnum, $keynum, '{}')");

        $write = true;

        $_SESSION['sessionid'] = my_encode($sidnum);

        $_SESSION['sessionkey'] = my_encode($keynum);

    }

    if ($write and $data) {

        pg_query("UPDATE hdaviz_sessions SET data='$insdata' WHERE id=$sidnum AND editkey=$keynum");

    } else {

        $rq = pg_query("SELECT data FROM hdaviz_sessions WHERE id=$sidnum");

        $l = pg_fetch_row($rq);

        $data = $l[0];

        pg_free_result($rq);

    }

    $resobj = array("data" => $data, "write_allowed" => $write, "sessionid" => $_SESSION['sessionid']);

    if ($write) {

        $resobj["sessionkey"] = $_SESSION['sessionkey'];

    }

echo json_encode($resobj);

?>