defmodule JOL.Blog do
  alias JOL.Blog.Post
  alias JOL.Blog.Parser

  defmodule NotFoundError do
    defexception [:message, plug_status: 404]
  end

  use NimblePublisher,
    build: JOL.Blog.Post,
    from: Application.app_dir(:jol, "priv/posts/**/*.md"),
    parser: Parser,
    as: :posts

  @posts Enum.sort_by(@posts, & &1.date, {:desc, Date})
  @tags @posts |> Enum.flat_map(& &1.tags) |> Enum.uniq() |> Enum.sort()

  def all_posts, do: @posts
  def unique_tag_list, do: @tags

  def recent_posts(num \\ 10) do
    Enum.take(all_posts(), num)
  end

  def get_post_by_slug!(slug) do
    Enum.find(all_posts(), &(&1.slug == slug)) ||
      raise NotFoundError, "post ``slug=#{slug}` not found"
  end

  def get_posts_by_tag!(tag) do
    case Enum.filter(all_posts(), &(tag in &1.tags)) do
      [] -> raise NotFoundError, "posts tagged `#{tag}` not found"
      posts -> posts
    end
  end
end