/* Before a reader route draws anything — /wiki/<slug> for an article,
   /wiki/<lang>/<slug> for one of its language versions — put the document it
   names on the library's shelf. On the server that is what lets the page in
   view be written out in the first HTML; on the client it is what the stack of
   open pages grows from, and the title the page is filed under. A page that is
   already on the shelf comes straight off it and is re-read in the background
   — so an edit made elsewhere still shows up when you turn to it. */

/** How a document is filed in the tab stack: which article, which language. */
function tabMeta(article: { slug: string; language?: string; baseSlug?: string | null }) {
  return { lang: article.language ?? 'en', identity: article.baseSlug || article.slug }
}

export default defineNuxtRouteMiddleware(async (to) => {
  const loc = parseReaderPath(to.path)
  if (!loc) return

  /* taken before any await, while the app context is certainly at hand */
  const library = useArticleLibrary()
  const tabs = useArticleTabs()

  const onShelf = loc.lang
    ? library.getVersion(loc.identity, loc.lang)
    : library.get(loc.identity)
  if (onShelf) {
    tabs.ensureTab(onShelf.slug, onShelf.title, tabMeta(onShelf))
    library.revalidate(loc.identity, loc.lang ?? undefined)
    return
  }

  const article = loc.lang
    ? await library.loadVersion(loc.identity, loc.lang)
    : await library.load(loc.identity)

  if (article) tabs.ensureTab(article.slug, article.title, tabMeta(article))
})