An inefficient way to download your App Dot Net posts using Elixir

adn_download.exs

Mix.install([{:httpoison, "~> 2.0"}])

defmodule ADNDownloader do
  require HTTPoison

  @base_url "https://adn.micro.blog/"

  def get_posts(user_name) do
    url = @base_url <> "users/" <> String.at(user_name, 0) <> "/" <> user_name <> ".txt"

    %HTTPoison.Response{body: body} = HTTPoison.get!(url)

    post_urls =
      body
      |> String.split("\n")

    post_urls
    |> Enum.reject(fn post_url -> !String.match?(post_url, ~r/json$/) end)
    |> Enum.map(fn post_url -> @base_url <> post_url end)
  end

  def get_json(url) do
    %HTTPoison.Response{body: body} = HTTPoison.get!(url)

    file =
      Regex.named_captures(~r/\/(?<post>[0-9]*\.json$)/, url)
      |> Map.get("post")

    filepath = File.cwd!() <> "/posts/" <> file
    IO.puts(filepath)
    {filepath, body}
  end
end

[user_name] = System.argv()
posts = ADNDownloader.get_posts(user_name)

File.mkdir!(File.cwd!() <> "/posts")

posts
|> Enum.map(&ADNDownloader.get_json(&1))
|> Enum.map(fn {filename, contents} -> File.write!(filename, contents) end)