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// helper function for twitter card stuff
// GET YOUTUBE ID FROM URL
function getYouTubeIdFromURL($url) {
  $pattern = '%(?:youtube(?:-nocookie)?\.com/(?:[^/]+/.+/|(?:v|e(?:mbed)?)/|.*[?&]v=)|youtu\.be/)([^"&?/ ]{11})%i';

  preg_match($pattern, $url, $matches);

  return isset($matches[1]) ? $matches[1] : false;
}

function fw_twitter_card_stuff() {

  global $post;
    $thumb = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), "medium" );
    $title = the_title_attribute( "echo=0" );
    $excerpt = strip_tags(get_the_excerpt($post->ID));

    // GLOBAL TWITTER CARD META
    $card_meta .= '<meta name="twitter:site" content="@TWITTERSITEUSER">' . "\n";
    $card_meta .= '<meta name="twitter:creator" content="@TWITTERSITEUSER">' . "\n";
    $card_meta .= '<meta name="twitter:title" content="' . $title . '">' . "\n";
    $card_meta .= '<meta name="twitter:domain" content="DOMAIN NAME"/>' . "\n";
    
    if ($excerpt) {
      $card_meta .= '<meta name="twitter:description" content="' . $excerpt . '">' . "\n";
    }

    if (has_post_thumbnail($post->ID)) {
      $card_meta .= '<meta name="twitter:image:src" content="' . $thumb[0] . '">' . "\n";
    }

    // TWITTER VIDEO PLAYER META
    // assumes here Advanced Custom Fields (get_field) and a custom field holding the YouTube URL
    if ( function_exists("get_field") && (get_field("new_video_url", $post->ID) || get_field("add_video_url", $post->ID)) ) {

      if (get_field("new_video_url", $post->ID) !== '') {
        $videourl = get_field("new_video_url", $post->ID);  
      } elseif (get_field("add_video_url", $post->ID) !== '') {
        $videourl = get_field("add_video_url", $post->ID); 
      }
      
      $embedurl = getYouTubeIdFromURL($videourl);
      $card_meta .= '<meta name="twitter:card" content="player">' . "\n";
      
      // SHOW THE EMBED VERSION OF THIS LINK
      $card_meta .= '<meta name="twitter:player" content="https://www.youtube.com/embed/' . $embedurl . '">' . "\n";
      $card_meta .= '<meta name="twitter:player:width" content="560">' . "\n";
      $card_meta .= '<meta name="twitter:player:height" content="315">' . "\n";
      $card_meta .= '<meta name="twitter:player:stream" content="https://www.youtube.com/embed/' . $embedurl . '">' . "\n";

    // IF NO VIDEO, LOOK FOR THUMBNAIL
    } elseif (has_post_thumbnail($post->ID)) {
      $card_meta .= '<meta name="twitter:card" content="summary_large_image">' . "\n";
    // IF NO THUMBNAIL, SHOW SUMMARY ONLY
    } else {
      $card_meta .= '<meta name="twitter:card" content="summary" />' . "\n";
    }
    return $card_meta;
}