<?php

///////////////////////////////////////////////////////////////////////
// AUTHOR : Husnu Yenigun (http://people.sabanciuniv.edu/yenigun)
// DATE   : May 12, 2005
// PURPOSE: This file reads the FREEBUSY entries in a vCalendar file
//          and displays free and busy times as an HTML table.
//          It can read a local file or a file that is passed as a
//          URL parameter.
//
// UPDATE : Nov 11, 2008 
//          It now displays the last modification time information of
//          the calendar file.
//
//////////////////////////////////////////////////////////////////////

/**********************************************************************
INSTALL GUIDE:
--------------
First of all you need a vCalendar file that contains your 
busy times. Outlook can produce this file periodically, hence you
can present your up-to-date busy-free times on the web.
A typical FREEBUSY file looks like this:

BEGIN:VCALENDAR
PRODID:-//Microsoft Corporation//Outlook 11.0 MIMEDIR//EN
VERSION:2.0
METHOD:PUBLISH
BEGIN:VFREEBUSY
ORGANIZER:Unknown
DTSTAMP:20050512T101638Z
DTSTART:20050430T210000Z
DTEND:20050831T210000Z
FREEBUSY:20050502T070000Z/20050502T090000Z
FREEBUSY:20050502T103000Z/20050502T120000Z
FREEBUSY:20050502T123000Z/20050502T133000Z
FREEBUSY:20050502T143000Z/20050502T150000Z
FREEBUSY:20050503T093000Z/20050503T113000Z
FREEBUSY:20050503T120000Z/20050503T123000Z
FREEBUSY:20050503T133000Z/20050503T140000Z
END:VFREEBUSY
END:VCALENDAR

The lines that start with FREEBUSY: are the time slots that are
busy.

In order to make Outlook produce this file automatically, go to 
  Tools -> Options -> Calendar Options -> Free/Busy Options
and mark "Publish at my location" and type in a path&filename
that can be seen by your web server. 

For the installation of calendar.php, you need to put this 
PHP file into the same path as your vCalendar file, and give a link 
to this PHP file and present your up-to-date free/busy times on the web.
There are some more configuration parameters, which are given and explained below. 
Using these parameters, you can change the colors of the page, the time that
the days start and end, and the length of the slots in the days.

**********************************************************************/

///////////////////////////////////////////////////////////////////////
// CONFIGURATION

// the name of vcalendar FREEBUSY file
$freeBusyFileName = 'http://people.sabanciuniv.edu/yenigun/hycalendar'; 
$freeBusyFileName2 = 'http://people.sabanciuniv.edu/yenigun/remotecalendar'; 

$daysStartAt = '08:00'; // The first slot that will be shown will start from this hour.
$daysEndAt   = '19:00'; // The last slot that will be shown will end at this hour.
$slotLength = 30;     // Length of slots in a day (minutes). 
// For example if you have
// $daysStartAt = '08:00'; 
// $daysEndAt   = '19:00'; 
// $slotLength = 30;    
// then the table will have rows corresponding to the time slots
//   08:00-08:30, 08:30-09:00, 09:00-09:30, etc.
// Note that, if a time slot intersects with a FREEBUSY time in the
// vCalendar file, then it will be shown as busy on the web page.
// For example, if your vCalendar vCalendar file includes shows a busy
// time between 09:45 and 10:15, then with the above configuration,
// both the time slot 09:30-10:00 and 10:00-10:30 will be marked
// as busy in the generated table. Therefore, you should adjust
// $daysStartAt and $slotLength so that your busy times align well
// with the generated table slots.

$showWeekend = false; // false: only weekdays are shown 
                     // true: full week is shown 

//$freeSlotBG = "#DDDDDD"; // Background color of the free slots 
$freeSlotBG = "#EEEE00"; // Background color of the free slots 
$busySlotBG = "#0000FF"; // Background color of the busy slots
$freeSlotFG = "#FFFFFF"; // Text color of the free slots 
$busySlotFG = "#FFFF00"; // Text color of the busy slots


$freeSlotText = ""; // What to display in free slots
$busySlotText = "BUSY"; // What to display in busy slots

$colHeaderBG = "#4B5579"; // Background color of the column headers
$rowHeaderBG = "#4B5579"; // Background color of the row headers
$colHeaderFG = "#FFFFFF"; // Text color of the column headers
$rowHeaderFG = "#FFFFFF"; // Text color of the column headers

$colWidth = 75; // column width in pixels

$vCalendarTimeOffset = 120; // For some reason, the times given in vCalendar file
                            // are shifted by a certain amount. This parameter
			    // (given in minutes) is used to fix this shift.
			    // We add vCalendarTimeOffset minutes to the times
			    // given in vCalendar file.

$yourName = "Husnu Yenigun";  // Your name and lastname

// You can give a message to be displayed below the table.
$yourMessage = "
  <b>For students:</b> To have an appointment, please find a free slot from 
  this calendar, and let me know the time. To complete the reservation,
  I'll send you an e-mail to confirm the time you picked. If you do not 
  have a confirmed reservation, then I cannot guarantee that you can find me,
  or I'll have time to talk to you when you show up at my office.";


$installPath = 'http://people.sabanciuniv.edu/yenigun/calendar.php';

///////////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////////////////////////
// NOTHING NEEDS TO BE CHANGED BELOW
//

function GetRemoteLastModified( $uri )
{
    // default
    $unixtime = 0;
    
    $fp = fopen( $uri, "r" );
    if( !$fp ) {return;}
    
    $MetaData = stream_get_meta_data( $fp );
        
    foreach( $MetaData['wrapper_data'] as $response )
    {
        // case: redirection
        if( substr( strtolower($response), 0, 10 ) == 'location: ' )
        {
            $newUri = substr( $response, 10 );
            fclose( $fp );
            return GetRemoteLastModified( $newUri );
        }
        // case: last-modified
        elseif( substr( strtolower($response), 0, 15 ) == 'last-modified: ' )
        {
            $unixtime = strtotime( substr($response, 15) );
            break;
        }
    }
    fclose( $fp );
    return $unixtime;
}


if (isset($_POST['week']))
   $week = $_POST['week'];
else
   $week = 0;

$noOfDays = ($showWeekend)?7:5;
$noOfSlots = 0;
$slots=array();

function vDate2StrDate ( $vDate ) {
  return strtotime(substr($vDate, 0, 4) . '-' . substr($vDate, 4, 2) . '-' . substr($vDate, 6, 2));
}

function vTime2Timestamp ( $vTime ) {
  $str = substr($vTime, 4, 2) . '/' . substr($vTime, 6, 2) . '/' . substr($vTime, 0, 4) . ' ' . substr($vTime, 9, 2) . ':' . substr($vTime, 11, 2);
  return strtotime($str);
}

function isWeekend( $dateStamp ) {
  // Given a date in the form of a stamp, it tells whether the stamp belongs 
  // to a weekday or not.
  return ((date("l",$dateStamp) == "Saturday") || (date("l",$dateStamp)=="Sunday"));
}

function prepareEmptySlots ($firstDay) {
// Prepare the empty slots for the week to be displayed
global $slots;
global $showWeekend;
global $noOfSlots;
global $daysStartAt;
global $daysEndAt;
global $slotLength;

  $fromDate = $firstDay;
  $toDate = $firstDay+6;

  for ($i = $fromDate; $i <= $toDate; $i++) {
      // For each day in the selected week


      // Get the date timestamp
      $date = strtotime("$i days");

      // Are we going to display this day?
      if ($showWeekend || !isWeekend($date)) {
         // Yes, we will...
  
         // The time stamp of the first slot's start time
         $firstSlotStarts = strtotime (date("m/d/y",$date) . " " . $daysStartAt);
  
         // The time stamp of the last slot's end time
         $lastSlotEnds = strtotime (date("m/d/y",$date) . " " . $daysEndAt);
  
         // Temporary time stamp for cruising
         $curSlotStarts = $firstSlotStarts;
  
         // Create the slots for this day
         while ($curSlotStarts < $lastSlotEnds) {
	    // The slot's start time
	    $slots[$noOfSlots]['start'] = $curSlotStarts;
  
	    // The slot's end time must be $slotLength*60 seconds later
	    $curSlotStarts += $slotLength*60;
	    $slots[$noOfSlots]['end'] = $curSlotStarts;
  
	    // Initially this slot is free
	    $slots[$noOfSlots]['status'] = 'free';
  
	    // and, we have formed a new slot
	    $noOfSlots++;
         }
      }
  }
}

// Find the current day of the week.
$todayIs = date('w');

// How many days ago did this week start?
$weekStartedDaysAgo = 1 - $todayIs; // We need negative offset, 1=Monday

// What is the first day of the week to be displayed?
$firstDay = $weekStartedDaysAgo + 7 * $week;

prepareEmptySlots ($firstDay);

// How many slots we have per day
$slotsPerDay = $noOfSlots / $noOfDays;

/////////////////////////////////////////////
// Process file generated by Outlook

// start from the first slot
$curSlot = 0;

// read the file and search for busy times
$lines = @file($freeBusyFileName);

if (!$lines) {
   // We could not open the calendar file...
   echo "Cannot open the calendar file --> $freeBusyFileName";
   exit;
   }
   
foreach ($lines as $line) {
   // process each line

   // Every line has two parts separated by a :
   list ($part1, $part2) = split(":",$line);

   if ($part1 == "DTSTART") { 
       // We found the first day of the calendar.
       $calendarStartDateStamp = vDate2StrDate($part2);
      }

   else if ($part1 == "DTEND") { 
       // We found the last day of the calendar.
       $calendarEndDateStamp = vDate2StrDate($part2);
      }

   else if ($part1 == "FREEBUSY") { 
      // We found a busy time.

      // A busy time has start and end times separated by a /
      list ($startDateTime, $endDateTime) = split("/", $part2);

      // Get the timestamp of the start time
      $startTimestamp = vTime2Timestamp($startDateTime) + $vCalendarTimeOffset*60;

      // Get the timestamp of the end time
      $endTimestamp = vTime2Timestamp($endDateTime) + $vCalendarTimeOffset*60;

      // Skip slots that do not intersect with the current busy time.
      while (($curSlot < $noOfSlots) && ($slots[$curSlot]['end'] <= $startTimestamp)) {
	 $curSlot++;
      }

      // Scan all the slots that have an interaction with the current busy time, and 
      // mark them as busy.
      while (($curSlot < $noOfSlots) && ($slots[$curSlot]['start'] < $endTimestamp)) {
         $slots[$curSlot]['status'] = 'busy';
	 $curSlot++;
      }
   }
}
/////////////////////////////////////////////
// Process remote file

$curSlot = 0;

// read the file and search for busy times
$lines = @file($freeBusyFileName2);

if (!$lines) {
   // We could not open the calendar file...
   echo "Cannot open the calendar file --> $freeBusyFileName2";
   exit;
   }
   
foreach ($lines as $line) {
   // process each line

   // Every line has two parts separated by a :
   list ($part1, $part2) = split(":",$line);

   if ($part1 == "FREEBUSY") { 
      // We found a busy time.

      // A busy time has start and end times separated by a /
      list ($startDateTime, $endDateTime) = split("/", $part2);

      // Get the timestamp of the start time
      $startTimestamp = vTime2Timestamp($startDateTime) + $vCalendarTimeOffset*60;

      // Get the timestamp of the end time
      $endTimestamp = vTime2Timestamp($endDateTime) + $vCalendarTimeOffset*60;

      // Skip slots that do not intersect with the current busy time.
      while (($curSlot < $noOfSlots) && ($slots[$curSlot]['end'] <= $startTimestamp)) {
	 $curSlot++;
      }

      // Scan all the slots that have an interaction with the current busy time, and 
      // mark them as busy.
      while (($curSlot < $noOfSlots) && ($slots[$curSlot]['start'] < $endTimestamp)) {
         $slots[$curSlot]['status'] = 'busy';
	 $curSlot++;
      }
   }
}

////////////////////////////////////////////////
////////////////////////////////////////////////

// Now we are ready to output the calendar
?>

<html>
<head>
<title>Calendar of <?=$yourName?></title>
<meta name="description" content="Converts a vCalendar file into an HTML table. It reads FREEBUSY items in the vCalendar file and outputs/generates an HTML table. The application is written using PHP. The required vCalendar files can be generated automatically.">
<meta name="keywords" content="vCalendar, free, busy, outlook, display, web, generate, html table, automatically">

<style type="text/css">

td.colHeader {
  background-color: <?=$colHeaderBG?>;
  border-width: 0px 0px 0px 0px;
  border-style : solid;
  color : <?=$colHeaderFG?>;
  text-align : center;
  font-size : 8pt;
  font-family : Verdana;
}

td.rowHeader {
  background-color: <?=$rowHeaderBG?>;
  border-width: 0px 0px 0px 0px;
  border-style : solid;
  color : <?=$rowHeaderFG?>;
  text-align : center;
  vertical-align : center;
  font-size : 8pt;
  font-family : Verdana;
}

td.busy {
  background-color: <?=$busySlotBG?>;
  border-width: 0px 0px 0px 0px;
  border-style : solid;
  color : <?=$busySlotFG?>;
  text-align : center;
  font-size : 8pt;
  font-family : Verdana;
  font-weight : bold;
}

td.free {
  background-color: <?=$freeSlotBG?>;
  border-width: 0px 0px 0px 0px;
  border-style : none;
  color : <?=$freeSlotFG?>;
  text-align : center;
  font-size : 8pt;
  font-family : Verdana;
  font-weight : bold;
}

.aButton {
background-color: #FFFFFF;
color: <?=$rowHeaderBG?>;
border: 0;
font-size: 8pt;
font-family: Verdana;
font-weight: bold;
}

.aLink {
background-color: #FFFFFF;
color: <?=$rowHeaderBG?>;
border: 0;
font-size: 8pt;
font-family: Verdana;
font-weight: bold;
}

.aDisabledButton {
background-color: #FFFFFF;
color: #AAAAAA;
border: 0;
font-size: 8pt;
font-family: Verdana;
font-weight: bold;
}

form {
  margin : 0px;
}

p.name {
background-color: #FFFFFF;
color: <?=$rowHeaderBG?>;
font-size: 10pt;
font-family: Verdana;
font-weight: bold;
}

p.message {
background-color: #FFFFFF;
color: <?=$rowHeaderBG?>;
font-size: 8pt;
font-family: Verdana;
font-weight: normal;
text-align: justify;
}
</style>

</head>
<body>
<center>

<?php
	echo '<p class="name">Calendar of ';
	echo $yourName;
	echo '</br>';
	echo '[for the period between ' . date('d/m/Y',$calendarStartDateStamp) . ' and ' . date('d/m/Y',$calendarEndDateStamp) . ']';
	echo '</p>';
?>

<table>
<!--  display navigation links -->
 <tr>
    <td width="<?=$colWidth?>px"></td>
    <td align="center" width="<?php echo $colWidth*(($showWeekend)?7:5);?>px" colspan="<?php echo (($showWeekend)?7:5);?>">
    <table width="100%">
    <tr>
         <td text-align="left" valign="bottom">
	 <?php
            // Calculate the dates that the previous week and next week buttons will show.
            $prevWeekStartsAt = strtotime($firstDay-7 . ' day');
            $prevWeekEndsAt = strtotime($firstDay-1-(($showWeekend)?0:2) . ' day');
            $nextWeekStartsAt = strtotime($firstDay+7 . ' day');
            $nextWeekEndsAt = strtotime($firstDay+13-(($showWeekend)?0:2) . ' day');

	    // Display the Previous Week, Current Week, Next Week buttons
	    // Pay attention to the dates that will be displayed by clicking previous and next buttons.
	    // If clicking them will go out of boundary of the available calendar, then the corresponding
	    // link should be grayed out.
            if ($prevWeekStartsAt <= $calendarEndDateStamp && $calendarStartDateStamp <= $prevWeekEndsAt) {
	       // We are within the boundary...
	    ?>
               <form action=<?=$installPath?><?php if ($URLcall) echo '?' . $URLparameters;?> method="POST">
               <input type="hidden" name="week" value="<?=$week-1?>">
	       <input align=left type="submit" value="<< Previous Week" class="aButton">
	     </form>
             <?php
	     }
	     else { 
	       // We are out of the boundary...
	       ?>
               <form action=<?=$installPath?><?php if ($URLcall) echo '?' . $URLparameters;?> method="POST">
               <input type="hidden" name="week" value="<?=$week?>">
	       <input align=left type="submit" value="<< Previous Week" class="aDisabledButton">
	     </form>
             <?php
	     }
	     ?>
	 </td>
         <td align="center" valign="bottom">
               <form action=<?=$installPath?><?php if ($URLcall) echo '?' . $URLparameters;?> method="POST">
	        <input type="hidden" name="week" value="0">
		<input type="submit" name="today" value="Current Week" class="aButton">
	      </form>
        </td>
        <td align="right">
	<?php
	    if ($nextWeekStartsAt <= $calendarEndDateStamp && $calendarStartDateStamp <= $nextWeekEndsAt) {
	       // We are within the boundary...
	      ?>
               <form action=<?=$installPath?><?php if ($URLcall) echo '?' . $URLparameters;?> method="POST">
                  <input type="hidden" name="week" value="<?=$week+1?>">
                  <input type="submit" value="Next Week >>" class="aButton">
               </form>
              <?php
              }
	      else {
	       // We are out of the boundary...
	      ?>
               <form action=<?=$installPath?><?php if ($URLcall) echo '?' . $URLparameters;?> method="POST">
                  <input type="hidden" name="week" value="<?=$week?>">
                  <input type="submit" value="Next Week >>" class="aDisabledButton">
		  </form>
	      <?php
	      }
	      ?>
        </td>
      </tr>
    </table>
    </td>
 </tr>
 <tr>
   <td width="<?=$colWidth?>px">
   </td>
<?php

    // Display dates, i.e. the column headings.
    for ($days = 0; $days < $noOfDays; $days++) {
        echo "<td width=\"" . $colWidth . "px\" class=\"colHeader\">";
	$dateStamp = $slots[$days*$slotsPerDay]['start'];
	if ($dateStamp < $calendarStartDateStamp || $dateStamp > $calendarEndDateStamp) {
           // This date is not within the period of the available calendar.
	   // Do not display the date.
	   echo '&nbsp;';
	   }
	else {
           // This date is within the period of the available calendar.
	   // Show the date and the day name.
	   echo date('d/m/y', $dateStamp);
	   echo '</br>';
	   echo date('l', $dateStamp);
	   }
	echo '</td>';
    }
    echo '</tr>';

    // Display slots as free or busy
    for ($slot = 0; $slot < $slotsPerDay; $slot++) {
	// For each slot in the days, create a row.
        echo '<tr>';
        echo "<td class=\"rowHeader\" width=\"" . $colWidth . "px\">";
        echo date('H:i', $slots[$slot]['start']);
	echo '-';
        echo date('H:i', $slots[$slot]['end']);
        echo '</td>';

        for ($day = 0; $day < $noOfDays; $day++ )  {
	    if ($slots[$day*$slotsPerDay+$slot]['status'] == 'busy') {
	       // This is a busy slot...

	       if ($slot == 0 || $slots[$day*$slotsPerDay+$slot-1]['status'] == 'free') {
		  // This is the first busy slot in a series.

		  // Count how many slot we have as busy
		  $tmpSlot = $slot+1;
		  while ($tmpSlot < $slotsPerDay && $slots[$day*$slotsPerDay+$tmpSlot]['status'] == 'busy')
		     $tmpSlot++;

	          echo '<td rowspan="'; 
		  echo $tmpSlot-$slot;
		  echo "\" class=\"busy\" width=\"" . $colWidth . "px\">";
	          echo $busySlotText;
		  }
	       }
	    else {
	       // This is a free slot, just create a free cell in the table.
	       echo "<td class=\"free\" width=\"" . $colWidth . "px\">";
	       echo $freeSlotText;
	       }

	    echo '</td>';
        }
        echo '</tr>';
	}
?>
</table>
<?php
  if (!$URLcall) {
    // then this is not a URL call hence we can display the message.
?>
<table>
<tr>
<td width="<?php echo $colWidth*(($showWeekend)?8:6);?>px" colspan="<?php echo (($showWeekend)?8:6);?>">
<p class="message">
<?=$yourMessage?>
</p>
</td>
<tr>
<td width="<?php echo $colWidth*(($showWeekend)?8:6);?>px" colspan="<?php echo (($showWeekend)?8:6);?>">

<?php
$thisfile = $freeBusyFileName;
if (!is_null($thisfile)) {
?>
<table cellpadding="1" cellspacing="1" border="1" width="100%">
   <tr>
     <td valign="top" align="center">
        <font color="#330033", face="Helvetica, Verdana, Arial, sans-serif", size="2">

<?php
$last_modified = GetRemoteLastModified($thisfile);

print "Calendar info last modified: " . date("l, dS F, Y @ h:ia", $last_modified);
?>
     </td> 
     </tr> 
     </table>
<?php
}
?>
</td>
</tr>
</table>
<?php
  }
?>
</center>

</body>
</html>