<?php

/**
 * RelativeTime - pretty printed
 *
 * @package Site5 Helpdesk
 * @author Dejan Marjanovic <dmarjanovic@site5.com>
 */
class Site5_RelativeTime
{

    private $interval = '';

    public function __construct()
    {
        call_user_func_array(array(__CLASS__, 'calculate'), func_get_args());
    }

    public function calculate($start, $end = NULL)
    {

        if ( empty($start))
            return false;

        if (empty($end))
            $end = time();

        if ( ! is_numeric($start))
            $start = strtotime($start);

        if ( ! is_numeric($end))
            $end = strtotime($end);

        if($start > $end)
            $future = TRUE;

        $start = '@' . $start;
        $end = '@' . $end;

        if ( ! ($start instanceof DateTime))
            $start = new DateTime($start);

        if ($end === null)
            $end = new DateTime();

        if ( ! ($end instanceof DateTime))
            $end = new DateTime($end);

        $interval = $end->diff($start);

        $get_plural = function($int, $str)
        {
            return $int > 1? $str.'s': $str;
        };

        $format = array();

        if ($interval->y !== 0)
            $format[] = "%y " . $get_plural($interval->y, "year");
        if ($interval->m !== 0)
            $format[] = "%m " . $get_plural($interval->m, "month");
        if ($interval->d !== 0)
            $format[] = "%d " . $get_plural($interval->d, "day");
        if ($interval->h !== 0)
            $format[] = "%h " . $get_plural($interval->h, "hour");
        if ($interval->i !== 0)
            $format[] = "%i " . $get_plural($interval->i, "minute");


        if ($interval->s !== 0)
        {
            if ( ! count($format))
            {
                $this->interval = "less than a minute";
                return;
            }
            else
            {
                $format[] = "%s " . $get_plural($interval->s, "second");
            }
        }

        if (count($format) > 1)
        {
            $format = array_shift($format) . " and " . array_shift($format);
        }
        else
        {
            $format = array_pop($format);
        }

        $tense = ($future === TRUE)? 'from now': 'ago';

        $this->interval = $interval->format($format) . ' ' . $tense;
    }

    public function __toString()
    {
        return $this->interval;
    }

}