feat: add protos compiler

apps/emqx_gateway/mix.exs

@@ -10,6 +10,8 @@ defmodule EMQXGateway.MixProject do
       deps_path: "../../deps",
       lockfile: "../../mix.lock",
       elixir: "~> 1.12",
+      compilers: [:protos | Mix.compilers()],
+      aliases: ["compile.protos": &protos/1],
       start_permanent: Mix.env() == :prod,
       deps: deps(),
       description: "The Gateway Management Application"
@@ -24,8 +26,33 @@ defmodule EMQXGateway.MixProject do
     ]
   end
 
+  defp protos(_args) do
+    app_path = Path.expand("..", __ENV__.file)
+    config = [
+      :use_packages,
+      :maps,
+      :strings_as_binaries,
+      rename: {:msg_name, :snake_case},
+      rename: {:msg_fqname, :base_name},
+      i: '.',
+      report_errors: false,
+      o: app_path |> Path.join("src/exproto") |> to_charlist(),
+      module_name_prefix: 'emqx_',
+      module_name_suffix: '_pb'
+    ]
+
+    app_path
+    |> Path.join("src/exproto/protos/*.proto")
+    |> Path.wildcard()
+    |> Enum.map(&to_charlist/1)
+    |> Enum.each(&:gpb_compile.file(&1, config))
+
+    :ok
+  end
+
   defp deps do
     [
+      {:gpb, "4.19.1", runtime: false},
       {:emqx, in_umbrella: true},
       {:lwm2m_coap, github: "emqx/lwm2m-coap", tag: "v2.0.0"},
       {:grpc, github: "emqx/grpc-erl", tag: "0.6.2"},