neiam /gitgud

defmodule GitGudWeb.Plugs.GitRouter do
  @moduledoc """
  Early-pipeline matcher that diverts `/:owner/:name.git/...` requests to
  `GitGudWeb.Plugs.GitSmartHttp`, bypassing Plug.Parsers (which would
  consume the body the CGI needs to read).
  """
  @behaviour Plug

  import Plug.Conn

  alias GitGudWeb.Plugs.GitSmartHttp

  @impl true
  def init(opts), do: opts

  @impl true
  def call(%Plug.Conn{path_info: path_info} = conn, _opts) do
    if git_request?(path_info) do
      conn
      |> fetch_query_params()
      |> GitSmartHttp.call(GitSmartHttp.init([]))
      |> halt()
    else
      conn
    end
  end

  # Divert git smart-HTTP (and LFS) requests to GitSmartHttp. Accept both
  # the `/:owner/:name.git/...` form and the bare `/:owner/:name/...`
  # form — `git clone <url>` and `actions/checkout` clone without a
  # `.git` suffix, so we key off the git service sub-path too, not just
  # the suffix. Bare `/:owner/:name/{info/refs,git-*,info/lfs}` doesn't
  # collide with any web route (those live under /r, /orgs, /users, …).
  defp git_request?([_owner, name | rest]) when is_binary(name) do
    String.ends_with?(name, ".git") or git_service_path?(rest)
  end

  defp git_request?(_), do: false

  defp git_service_path?(["info", "refs" | _]), do: true
  defp git_service_path?(["git-upload-pack" | _]), do: true
  defp git_service_path?(["git-receive-pack" | _]), do: true
  defp git_service_path?(["info", "lfs" | _]), do: true
  defp git_service_path?(_), do: false
end