<?php
// On Windows Machines %V doesn't seem to work, 
// so we're using %W (though it's not ISO-compliant)
if (strftime("%V") === false) {
    define("CALENDAR_WEEK_FORMAT","%W");
} else {
    define("CALENDAR_WEEK_FORMAT","%V");
}
/**
 * Class Calendar
 * @author Stefan Walk <kyrael@web.de>
 * @version 0.1
 **/
class Calendar
{
    /**
     * Used to store layout information.
     * @var layout array
     * @access private
     **/
    var $layout = array(
        'table_start'              => '<table>', 
        'table_end'                => '</table>', 
        'row_start'                => '<tr>', 
        'row_end'                  => '</tr>', 
        'cell_start'               => '<td>', 
        'cell_end'                 => '</td>', 
        'cell'                     => '%d',
        'empty_cell_start'         => '<td>', 
        'empty_cell_end'           => '</td>', 
        'empty_cell'               => '&nbsp;',
        'week_cell_start'          => '<td>', 
        'week_cell_end'            => '</td>', 
        'week_cell'                => CALENDAR_WEEK_FORMAT,
        'corner_cell_start'        => '<td>', 
        'corner_cell_end'          => '</td>', 
        'corner_cell'              => '&nbsp;',
        'head_cell_start'          => '<td>', 
        'head_cell_end'            => '</td>', 
        'head_cell'                => '%s',
        'title_cell_start'         => '<td %colspan%>', 
        'title_cell_end'           => '</td>', 
        'title_cell'               => '%B %Y',
        'day_of_week_names'        => array(
            'Mon','Tue','Wed','Thu','Fri','Sat','Sun'
            ),
        'print_days_of_week'       => true,
        'print_title'              => true,
        'print_number_of_week'     => true
        );
    
    /**
     * Used to store event information.
     * @var events array
     * @access private
     **/
    var $events = array(
        'day'      => array(),
        'interval' => array(),
        'periodic' => array()
        );
    
    /**
     * Calendar::setLayout()
     * 
     * Alters the default layout.
     * 
     * @access public
     * @param $layout array
     * @return bool
     **/
    function setLayout($layout)
    {
        if (is_array($layout)) {
            $this->layout = array_merge($this->layout, $layout);
            return true;
        } else {
            trigger_error('Calendar::setLayout - Argument was not an array',
                          E_USER_NOTICE);
            return false;
        }
    }
    
    /**
     * Calendar::addDate()
     * 
     * Adds an event entry for a specific day.
     * 
     * @access public
     * @param $date string
     * @param $layout array
     * @return bool
     **/
    function addDate($date, $layout)
    {
        if (!is_array($layout)) {
            trigger_error('Calendar::addDate - Layout arg. was not an array',
                          E_USER_WARNING);
            return false;
        }
        $time = strtotime($date);
        if ($time == -1) {
            trigger_error('Calendar::addDate - Failed to parse date argument',
                          E_USER_WARNING);
            return false;
        }
        $this->events['day'][$time]['layout'] = $layout;
        return true;
    }

    /**
     * Calendar::addInterval()
     * 
     * Adds an event entry for a period of time.
     * 
     * @access public
     * @param $start string
     * @param $end string
     * @param $layout array
     * @return bool
     **/
    function addInterval($start, $end, $layout)
    {
        if (!is_array($layout)) {
            trigger_error('Calendar::addInterval - Layout arg. was no array',
                          E_USER_WARNING);
            return false;
        }
        $start = strtotime($start);
        $end   = strtotime($end);
        if ($start == -1 or $end == -1) {
            trigger_error('Calendar::addInterval - Failed to parse dates',
                          E_USER_WARNING);
            return false;
        }
        $this->events['interval'][] = array(
            'start'  => $start,
            'end'    => $end,
            'layout' => $layout
            );
        return true;
            
    }

    /**
     * Calendar::addPeriodic()
     * 
     * Add an entry for an event that occurs periodically.
     * 
     * @access public
     * @param $format string
     * @param $match string
     * @param $layout array
     * @return bool
     **/
    function addPeriodic($format, $match, $layout)
    {
        if (!is_array($layout)) {
            trigger_error('Calendar::addPeriodic - Layout arg. was no array',
                          E_USER_WARNING);
            return false;
        }
        $this->events['periodic'][] = array(
            'format'  => $format,
            'match'   => $match,
            'layout'  => $layout
            );
        return true;
    }
    
    /**
     * Calendar::checkPeriodics()
     * 
     * Function used internally, returns an array of all periodic events that
     * match the timestamp $date given as an argument.
     * Currently breaks off at the first match for speed reasons cause it's 
     * at the moment impossible to handle multiple events for one day, anyway.
     * 
     * @access private
     * @param $date int
     * @return array
     **/
    function checkPeriodics($date)
    {
        $return = array();
        foreach ($this->events['periodic'] as $key => $periodic) {
            if (strftime($periodic['format'], $date) == $periodic['match']) {
                $return[] = $key;
                return $return; // remove this as soon as multiple events for
                                // one day are implemented!
            }
        }
        return $return;
    }
    
    /**
     * Calendar::checkIntervals()
     * 
     * Function used internally, returns an array of all periods of time that
     * contain the timestamp $date given as an argument.
     * Currently breaks off at the first match for speed reasons cause it's 
     * at the moment impossible to handle multiple events for one day, anyway.
     * 
     * @access private
     * @param $date int
     * @return array
     **/
    function checkIntervals($date)
    {
        $return = array();
        foreach ($this->events['interval'] as $key => $ival) {
            if ($ival['start'] <= $date &&
                $ival['end']   >= $date ) {
                $return[] = $key;
                return $return; // remove this as soon as multiple events for
                                // one day are implemented!
            }
        }
        return $return;
    }
    
    /**
     * Calendar::getWeekDays()
     * 
     * Returns an array containing the names of the days of the week using the
     * current locale and the format given as the argument. $format should be
     * a valid format for use with strftime()
     * 
     * @access public
     * @param $format string
     * @return array
     **/
    function getWeekDays($format)
    {
        $weekdays = array();
        $time   = strtotime("next Monday");
        for ($i=0; $i<7; $i++) {
            $weekdays[] = strftime($format, $time);
            $time = strtotime("+1 day", $time);
        }
        return $weekdays;
        
    }
    
    /**
     * Calendar::fetch()
     * 
     * Returns a string containing the calendar for the year and month given
     * as arguments. $year should be between 1971 and 2037, $month should be
     * between 1 and 12. Returns false on error. 
     * 
     * @access public
     * @param $year int
     * @param $month int
     * @return string
     **/
    function fetch($year, $month)
    {
        if (!is_numeric($year) || !is_numeric($month)) {
            trigger_error('Calendar::fetch - Arguments should be numbers',
                           E_USER_WARNING);
            return false;
        }
        // remove heading zeros
        $year = (int)$year;
        $month = (int)$month;
        if ($year < 1971 or $year > 2037) {
            trigger_error('Calendar::fetch - Year is not between 1971 and 2037',
                           E_USER_WARNING);
            return false;
        }
        if ($month < 1 or $month > 12) {
            trigger_error('Calendar::fetch - Month should be between 1 and 12',
                           E_USER_WARNING);
            return false;
        }
        // getting variables from property to make handling easier    
        extract($this->layout);
        // initializing
        $calendar = '';
        $start_time = strtotime("$year-$month-1");
        if ($start_time == -1) {
            trigger_error('Calendar::fetch - Invalid Arguments passed',
                           E_USER_WARNING);
            return false;
        }    
        $start_dow  = ((int)strftime('%w', $start_time)+6)%7+1;
        $days_of_month = (int)date('t', $start_time);
        $calendar .= $table_start;
        // add the title
        if ($print_title) {
            $cols = $print_number_of_week ? 8 : 7;
            $calendar .= str_replace('%colspan%',
                                     " colspan=\"$cols\" ",
                                     $title_cell_start).
                         strftime($title_cell, $start_time).
                         $title_cell_end;
        }
        // add the head
        if ($print_days_of_week) {
            $calendar .= $row_start;
            if ($print_number_of_week) {
                $calendar .= $corner_cell_start.$corner_cell.$corner_cell_end;
            }
            foreach ($day_of_week_names as $name_of_day) {
                $calendar .= $head_cell_start.
                             sprintf($head_cell, $name_of_day).
                             $head_cell_end;
            }
            $calendar .= $row_end;
        }
        // filling heading empty cells in
        $calendar .= $row_start;
        if ($print_number_of_week) {
            $calendar .= $week_cell_start.
                         strftime($week_cell, $start_time).
                         $week_cell_end;
        }
        for ($i = 1; $i < $start_dow; $i++) {
            $calendar .= $empty_cell_start.$empty_cell.$empty_cell_end;
        }
        // add the cells
        for($i = 1; $i <= $days_of_month; $i++) {
            $time = strtotime("$year-$month-$i");
            $day_of_week = ((int)strftime('%w', $time)+6)%7+1;
            // new week means new row, but not if the first day falls on monday
            if ($day_of_week == 1 AND $i != 1) {
                $calendar .= $row_end.$row_start;
                if ($print_number_of_week) {
                    $calendar .= $week_cell_start.
                                 strftime($week_cell, $time).
                                 $week_cell_end;
                }
            }
            // special day?
            if (isset($this->events['day'][$time])) {
                $layout = array_merge($this->layout, 
                                      $this->events['day'][$time]['layout']
                                      );
                $calendar .= $layout['cell_start'].
                             strftime($layout['cell'], $time).
                             $layout['cell_end'];
            // some periodic event?
            } elseif((@list($per) = $this->checkPeriodics($time)) != array()) {
                $layout = array_merge($this->layout, 
                                      $this->events['periodic'][$per]['layout']
                                      );
                $calendar .= $layout['cell_start'].
                             strftime($layout['cell'], $time).
                             $layout['cell_end'];
            // special interval?
            } elseif((@list($ival) = $this->checkIntervals($time)) != array()) {
                $layout = array_merge($this->layout, 
                                      $this->events['interval'][$ival]['layout']
                                      );
                $calendar .= $layout['cell_start'].
                             strftime($layout['cell'], $time).
                             $layout['cell_end'];
            // boring normal day
            } else {
                $calendar .= $cell_start.
                             strftime($cell, $time).
                             $cell_end;
            }
        }
        // trailing empty cells
        for ($i = $day_of_week + 1; $i <= 7; $i++) {
            $calendar .= $empty_cell_start.$empty_cell.$empty_cell_end;
        }
        $calendar .= $row_end;
        $calendar .= $table_end;
        return $calendar;
        
    }
    
    /**
     * Calendar::display()
     * 
     * Prints the calendar for the year and month given as arguments.
     * $year should be between 1971 and 2037, $month should be between 1 and 12.
     * Returns true on success, false on error. 
     * 
     * @access public
     * @param $year int
     * @param $month int
     * @return bool
     **/
    function display($year, $month)
    {
        $calendar = $this->fetch($year, $month);
        if (empty($calendar)) {
            return false;
        } else {
            print $calendar;
            return true;
        }
    }
}
?>