Displaying a Wikipedia article page

The player has read the starting article and clicked on a link within the content. We need to add the logic for rendering the linked article. We'll have to fetch the article (or read it from the database if it was already fetched), display it, and update the game's state.

Here is the code:

const articlepage = HTTP.HandlerFunction() do req 
  uri_parts = parseuri(req.target) 
  game = gamesession(uri_parts[1]) 
  article_uri = "/wiki/$(uri_parts[end])" 
  existing_articles = Articles.find(article_uri) 
  article = isempty(existing_articles) ?  
    persistedarticle(fetchpage(article_uri)...) :  
    existing_articles[1] 
  push!(game.history, article) 
  game.steps_taken += 1 
  puzzlesolved(game, article) && destroygamesession(game.id) 
  HTTP.Messages.Response(200, wikiarticle(game, article)) 
end

We start by parsing...