Add basic forwarding/multiplexing functionality

lib/peer.ex

@@ -0,0 +1,79 @@
+defmodule Frajtano.Peer do
+  alias Frajtano.Proto
+  require Logger
+  use GenServer, restart: :temporary
+
+  def start(path) do
+    DynamicSupervisor.start_child(Frajtano.Peer, {__MODULE__, path})
+  end
+
+  def start_link(path) do
+    GenServer.start_link(__MODULE__, path)
+  end
+
+  @impl true
+  def init(path) do
+    {:ok, conn} = :gen_tcp.connect({:local, path}, 0, [:binary, active: :once])
+    {:ok, %{conn: conn, clients: :queue.new(), buffer: <<>>}}
+  end
+
+  @impl true
+  def handle_call(packet, from, %{conn: conn, clients: clients} = state) do
+    case :gen_tcp.send(conn, Proto.encode(packet)) do
+      :ok ->
+        {:noreply, %{state | clients: :queue.in(from, clients)}}
+
+      {:error, :closed} ->
+        {:noreply, state, {:continue, :closed}}
+
+      {:error, e} ->
+        raise(e)
+    end
+  end
+
+  defp handle_messages(%{clients: clients, buffer: buffer} = state) do
+    case Proto.decode(buffer) do
+      {nil, buffer} ->
+        {:noreply, %{state | buffer: buffer}}
+
+      {msg, buffer} ->
+        {{:value, client}, clients} = :queue.out(clients)
+        GenServer.reply(client, {:ok, msg})
+        handle_messages(%{state | clients: clients, buffer: buffer})
+    end
+  end
+
+  @impl true
+  def handle_info({:tcp, conn, msg}, %{conn: conn, buffer: buffer} = state) do
+    :inet.setopts(conn, active: :once)
+    buffer = buffer <> msg
+
+    handle_messages(%{ state | buffer: buffer })
+  end
+
+  @impl true
+  def handle_info({:tcp_closed, _}, state) do
+    {:noreply, state, {:continue, :closed}}
+  end
+
+  @impl true
+  def handle_continue(:closed, %{clients: clients}) do
+    clients
+    |> :queue.to_list()
+    |> Enum.each(&GenServer.reply(&1, {:error, :closed}))
+
+    {:stop, :closed, %{}}
+  end
+
+  def identities(peer) do
+    with {:ok, {:agent_identities_answer, identities}} <-
+           GenServer.call(peer, {:agentc_request_identities, nil}),
+         do: {:ok, identities}
+  end
+
+  def sign(peer, request) do
+    with {:ok, {:agent_sign_response, signature}} <-
+           GenServer.call(peer, {:agentc_sign_request, request}),
+         do: {:ok, signature}
+  end
+end