Class to generate Calendar URLs and files

add-to-diary.php

<?php

/**
 * Utility for adding an event to various calendars
 *
 * @package SMRC
 */

if (isset($_POST['smrc_add_to_diary'])) {
  $event = new SMRC_Diary_Event($_POST);
  $event->handle();
}

class SMRC_Diary_Event {
  const DT_FORMAT = 'Ymd';
  const GOOGLE = 'https://calendar.google.com/calendar/render';
  const OUTLOOK = 'https://outlook.live.com/owa/';
  const YAHOO = 'https://calendar.yahoo.com/';

  protected $user = [];
  protected $properties = [];
  private $available_properties = [
    'title',          // all
    'start',          // all
    'end',            // all
    'description',    // all
    'location',       // all
    'timezone',       // google and iCal
    'url',            // iCal
    'organizer_name', // google and iCal
    'organizer_url'   // google and iCal
  ];

  /**
   * Object creation
   */
  public function __construct($properties)
  {
    $this->user = $properties;
    $this->properties = [
      'description'     => '',
      'location'        => '',
      'timezone'        => 'Europe/London',
      'organizer_name'  => 'Scottish Motor Racing Club',
      'organizer_url'   => 'https://smrc.co.uk'
    ];

    $this->set($properties);
    $this->addons();
  }

  public function set($key, $val = false)
  {
    if (is_array($key)) {
      foreach ($key as $k => $v) {
        $this->set($k, $v);
      }
    } else {
      if (in_array($key, $this->available_properties)) {
        $this->properties[$key] = $this->sanitize($val, $key);
      }
    }
  }

  private function addons()
  {
    if (!isset($this->properties['end'])) {
      $this->properties['end'] = $this->properties['start'];
    }
    $end_plus_one = new DateTime($this->properties['end']);
    $end_plus_one->modify('+1 day');
    $this->properties['end+1'] = $end_plus_one->format('Ymd');
  }

  /**
   * Object output
   */
  public static function form($args, $class_base = 'o-calendarAdd')
  {
    $class_base = esc_attr($class_base);

    $out = '<form target="_blank" method="post" class="' . $class_base . '">';
    $out .= '  <input type="hidden" name="smrc_add_to_diary" value="">';
    foreach ($args as $key => $val) {
      $out .= '<input type="hidden" name="' . esc_attr($key) . '" value="' . esc_attr($val) . '">';
    }

    $buttons = [
      ['Google Calendar', 'google', 'google'],
      ['Apple Calendar', 'apple', 'ics'],
      ['Outlook.com', 'outlook', 'outlook'],
      ['Yahoo!', 'yahoo', 'yahoo'],
      ['Microsoft Office Outlook', 'outlook', 'ics']
    ];
    $out .= '  <div class="' . $class_base . '__list">';
    foreach ($buttons as $button) {
      $out .= '  <button type="submit" name="' . $button[2] . '" title="' . $button[0] . '" class="' . $class_base . '__button">';
      $out .=    TCA_Icons::get($button[1], $class_base . '__icon', false);
      $out .= '  <span class="sr-only">' . $button[0] . '</span>';
      $out .= '  </button>';
    }
    $out .= '  </div>';
    $out .= '</form>';

    echo $out;
  }

  public function handle()
  {
    if (isset($_POST['google'])) {
      header('Location: ' . $this->google());

    } else if (isset($_POST['outlook'])) {
      header('Location: ' . $this->outlook());

    } else if (isset($_POST['outlook'])) {
      header('Location: ' . $this->outlook());

    } else if (isset($_POST['yahoo'])) {
      header('Location: ' . $this->yahoo());

    } else if (isset($_POST['ics'])) {
      header('Content-Type: text/calendar; charset=utf-8');
      header('Content-Disposition: attachment; filename=event.ics');

      echo $this->ics();
    }

    exit;
  }

  /**
   * Generation
   */
  public function google()
  {
    $organizer_url = preg_replace('#^https?://#', '', rtrim($this->properties['organizer_url'],'/'));
    $sprop = 'sprop=website:' . $organizer_url . '&sprop=name:' . $this->properties['organizer_name'];

    $args = [
      'action'    => 'TEMPLATE',
      'text'      => $this->properties['title'],
      'dates'     => $this->properties['start'] . '/' . $this->properties['end+1'],
      'ctz'       => $this->properties['timezone'],
      'details'   => $this->properties['description'],
      'location'  => $this->properties['location'],
      'sprop'     => $sprop
    ];

    $query = http_build_query($args, null, '&', PHP_QUERY_RFC3986);
    $google = self::GOOGLE . '?' . $query;

    return $google;
  }

  public function outlook()
  {
    $args = [
      'path'      => '/calendar/action/compose',
      'rru'       => 'addevent',
      'startdt'   => $this->properties['start'],
      'enddt'     => $this->properties['end'],
      'subject'   => $this->properties['title'],
      'allday'    => 'true',
      'body'      => $this->properties['description'],
      'location'  => $this->properties['location']
    ];

    $query = http_build_query($args, null, '&', PHP_QUERY_RFC3986);
    $outlook = self::OUTLOOK . '?' . $query;

    return $outlook;
  }

  public function yahoo()
  {
    $args = [
      'v'       => 60,
      'title'   => $this->properties['title'],
      'st'      => $this->properties['start'],
      'desc'    => $this->properties['description'],
      'in_loc'  => $this->properties['location'],
      'rem1'    => '1D'
    ];
    if ($this->properties['start'] === $this->properties['end']) {
      $args['dur'] = 'allday';
    } else {
      $args['et'] = $this->properties['end+1'];
    }

    $query = http_build_query($args, null, '&', PHP_QUERY_RFC3986);
    $yahoo = self::YAHOO . '?' . $query;

    return $yahoo;
  }

  public function ics()
  {
    // add header
    $ics_props = [
      'BEGIN:VCALENDAR',
      'VERSION:2.0',
      'PRODID:-//SMRC//NONSGML SMRC.CO.UK//EN',
      'CALSCALE:GREGORIAN',
      'BEGIN:VEVENT'
    ];

    $props = [
      'STATUS'              => 'CONFIRMED',
      'SUMMARY'             => $this->ics_escape($this->properties['title']),
      'DTSTART;VALUE=DATE'  => $this->properties['start'],
      'DTEND;VALUE=DATE'    => $this->properties['end+1'],
      'LOCATION'            => $this->ics_escape($this->properties['location']),
      'DESCRIPTION'         => $this->ics_escape($this->properties['description']),
      'URL;VALUE=URI'       => $this->properties['url'],
      'DTSTAMP'             => $this->format_time('now', 'Ymd\THis\Z'),
      'UID'                 => uniqid()
    ];

    $props['X-ALT-DESC;FMTTYPE=text/html'] = $props['DESCRIPTION'];

    // append properties
    foreach ($props as $k => $v) {
      $line = wordwrap("$k:$v", 74, "\r\n ");
      $ics_props[] = $line;
    }

    // append properties not fitting with common format
    $ics_props[] = 'ORGANIZER;CN=' . $this->ics_escape($this->properties['organizer_name']) . ':' . $this->properties['organizer_url'];

    // add reminder
    $ics_props[] = 'BEGIN:VALARM';
    $ics_props[] = 'TRIGGER:-PT1D';
    $ics_props[] = 'ACTION:DISPLAY';
    $ics_props[] = 'DESCRIPTION:Reminder';
    $ics_props[] = 'END:VALARM';

    // add footer
    $ics_props[] = 'END:VEVENT';
    $ics_props[] = 'END:VCALENDAR';

    return implode("\r\n", $ics_props);
  }

  /**
   * Utility functions
   */
  private function sanitize($val, $key = false)
  {
    switch ($key) {
      case 'start':
      case 'end':
        return $this->format_time($val);
    }
    return esc_attr($val);
  }

  private function format_time($time, $format = self::DT_FORMAT)
  {
    $dt = new DateTime($time);
    return $dt->format($format);
  }

  private function ics_escape($str) {
    return preg_replace('/([\,;])/','\\\$1', $str);
  }
}