Restructure Web/HTTP handling, statically serve acme-challenge dir

config/config.exs

@@ -2,5 +2,6 @@ import Config
 
 config :ha_handler,
 	http_port: 4000,
+	acme_challenge_path: "acme-challenge",
 	haproxy_socket: System.get_env("HAPROXY_SOCKET") || "/var/run/haproxy.sock"
 

lib/ha_handler.ex

@@ -3,4 +3,5 @@ defmodule HAHandler do
 
   def http_port, do: Application.get_env(:ha_handler, :http_port)
   def haproxy_socket, do: Application.get_env(:ha_handler, :haproxy_socket)
+  def acme_challenge_path, do: Application.get_env(:ha_handler, :acme_challenge_path)
 end

lib/ha_handler/application.ex

@@ -10,7 +10,7 @@ defmodule HAHandler.Application do
   @impl true
   def start(_type, _args) do
     children = [
-      {Plug.Cowboy, scheme: :http, plug: HAHandler.Web, options: [port: http_port()]}
+      {Plug.Cowboy, scheme: :http, plug: HAHandler.Web.Router, options: [port: http_port()]}
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html

lib/ha_handler/web/controller.ex

@@ -1,13 +1,9 @@
-defmodule HAHandler.Web do
+defmodule HAHandler.Web.Controller do
 	import Plug.Conn
 
 	alias HAHandler.HAProxy
 
-	def init(opts) do
-		opts
-	end
-
-	def call(conn, _opts) do
+	def index(conn) do
 		{:ok, hostname} = :inet.gethostname()
 
 		stats = HAProxy.get_stats()

lib/ha_handler/web/router.ex

@@ -0,0 +1,35 @@
+defmodule HAHandler.Web.Router do
+	@moduledoc """
+	This module dispatch incoming HTTP requests to their
+	related logic. Please refer to [1] for details.
+
+	[1] https://hexdocs.pm/plug/Plug.Router.html#content
+	"""
+
+	use Plug.Router
+
+	import HAHandler, only: [acme_challenge_path: 0]
+
+	alias HAHandler.Web.Controller
+
+	# Note for plugs: oder is important, as a plug may stop
+	# want to stop the pipeline!
+
+	plug Plug.Logger, log: :debug
+	# Note: `plug` is a macro, hence evaluated at
+	# compile-time. The configuration (which path to
+	# serve) cannot be modified at runtime with this
+	# system.
+	plug Plug.Static,
+		at: "/.well-known/acme-challenge/",
+		from: acme_challenge_path()
+
+	plug :match
+	plug :dispatch
+
+	get "/", do: Controller.index(conn)
+
+	match _ do
+		send_resp(conn, 404, "Not found")
+	end
+end