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Jelly Shot

A semi static blog engine

starting point

Static markdown blog by @seilund

A million static site generators...

💁 let's write another one

• Phoenix
• No database
• No static file generation

• Compiling markdown into %Post{}s
• Have a GenServer deliver them

Let's take this further

• Generator -> markdown |> struct
• Repository -> Agent storing data
• Watcher -> GenServer for auto update

Generator

defp compile_file(file) do
  with{:ok, matter, body} <- split_frontmatter(file),
      {:ok, html, _} <- Earmark.as_html(body),
  do: {:ok, into_post(file, matter, html)}
end

defp into_post(file, meta, html) do
  data = %{
    slug: file_to_slug(file),
    content: html,
  } |> Map.merge(meta)

  struct(JellyShot.Post, data)
end

Repository

def start_link do
  Agent.start_link(&get_initial_state/0, name: __MODULE__)
end

posts = File.ls!("priv/posts")
|> Enum.filter(&(Path.extname(&1) == ".md"))
|> Enum.map(&compile_async/1)
|> Enum.map(&Task.await/1)
|> Enum.reduce([], &valid_into_list/2)
|> Enum.sort(&sort/2)

Watcher

def init(state) do
  path = Path.expand("priv/posts")

  :fs.start_link(:fs_watcher, path)
  :fs.subscribe(:fs_watcher)

  {:ok, state}
end

def handle_info({_pid, {:fs, :file_event}, {path, ev}}, _) do
  new_state = cond do
    Enum.member?(ev, :modified) ->
      path
      |> JellyShot.Post.file_to_slug
      |> JellyShot.Repo.upsert_by_slug
  end
end

Integrating into Phoenix 🐣🔥

Listing posts

def index(conn, params) do
  {tmpl, headline, {:ok, posts}} = case params do
    %{"author" => author} ->
      {"list", "by author",  Repo.get_by_author(author)}
    %{"category" => category} ->
      {"list", "by category", Repo.get_by_category(category)}
    _ ->
      {"index", "recent posts", Repo.list()}
  end

  render conn, "#{tmpl}.html", head: head, posts: posts
end

Limitations

Filling the repository...

~ 250 sloc / file

• 12 posts in 406ms 🐰
• 384 posts in 3844ms 🐢
• ... 🐌

We might hit a cap at some point

Anyway, I Learned a lot

• Pattern matching
• Agents
• GenServer
• with {:ok}

Thanks

https://github.com/erikmueller/jelly_shot

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