sclass HTMLFramer1 {
  S title;
  new L<NavItem> navItems;
  new LS contents;
  new LS headElements;

  srecord NavItem(S link, S html) {
    bool targetBlank;
  }
  
  swappable S render() {
    ret hhtml(hhead(htitle(title)
      + lines(headElements))
      + hbody(h1(htmlEncode2(title))
      + renderNav()
      + lines(contents)));
  }
  
  swappable S renderNav() {
    if (empty(navItems)) ret "";
    ret p(joinWithVBar(map(navItems, ni -> ahref_possiblyTargetBlank(ni.link, ni.html, ni.targetBlank))));
  }
  
  void addNavItem(S html) {
    navItems.add(new NavItem(null, html));
  }
  
  void addNavItem(S link, S html, O... _) {
    navItems.add(setAll(new NavItem(link, html), filterParams(_, 'targetBlank)));
  }
  
  void addInHead(O html) {
    headElements.add(str(html));
  }
  
  // add contents: TODO move things to head automatically
  void add(O html) {
    addIfNempty(contents, strOrEmpty(html));
  }
}