Bone

<IfModule mod_rewrite.c>
RewriteEngine on

RewriteCond &%{QUERY_STRING} ^(?=.*&w=(\d+))(?=.*&h=(\d+))
RewriteCond %{DOCUMENT_ROOT}/resized/$1_%1_%2.$2 -f
RewriteRule ^(original/.+)\.(.+) /resized/$1_%1_%2.$2 [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /resizer.php?path=$1 [L,QSA]
</IfModule>

interface PostAttachVideo {
  type: 'video'
  attach: AttachVideo
}

interface PostAttachAudio {
  type: 'audio'
  attach: AttachAudio
}

type PostAttach = PostAttachAudio | PostAttachVideo

function isAudio(attach: PostAttach): attach is PostAttachAudio {
    return attach.type === 'audio';
}

interface BookAuthor { ... }
interface BookPrice { ... }
interface Book {
  id: number,
  author: BookAuthor,
  price: BookPrice
}