{{- $postTarget := printf "/sites/%v/posts" .site.ID -}}
{{- if (ne .post.ID 0) -}}
    {{- $postTarget = printf "/sites/%v/posts/%v" .site.ID .post.ID -}}
{{- end -}}
<form method="post" action="{{$postTarget}}" class="post-form">
    <input name="title" placeholder="Title" value="{{.post.Title}}">

    <textarea name="body">{{.post.Body}}</textarea>

    <div class="bottom-bar">
        <input type="submit" value="Post">
    </div>
</form>