Add support for spawning peers, and monitoring the processes

lib/agent.ex

@@ -56,9 +56,8 @@ defmodule Frajtano.Agent do
   end
 
   @impl true
-  def handle_call({:add_peer, path}, _from, state) do
-    # TODO: deduplicate peers by socket path
-    case Peer.start(path) do
+  def handle_call({:add_peer, spec}, _from, state) do
+    case Peer.start(spec) do
       {:ok, _} -> {:reply, :ok, state}
       {:error, error} -> {:reply, {:error, error}, state}
     end
@@ -73,7 +72,11 @@ defmodule Frajtano.Agent do
     GenServer.call(__MODULE__, {:sign, request}, :infinity)
   end
 
-  def add_peer(path) do
-    GenServer.call(__MODULE__, {:add_peer, path})
+  def assimilate(path) do
+    GenServer.call(__MODULE__, {:add_peer, {:socket, path}})
+  end
+
+  def spawn_peer(spec) do
+    GenServer.call(__MODULE__, {:add_peer, {:spawn, spec}}) 
   end
 end

lib/peer.ex

@@ -3,20 +3,59 @@ defmodule Frajtano.Peer do
   require Logger
   use GenServer, restart: :temporary
 
-  def start(path) do
-    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {__MODULE__, path})
+  defmodule Spawner do
+    use Supervisor, restart: :permanent
+
+    def start_link(spec) do
+      Supervisor.start_link(__MODULE__, spec, [])
+    end
+
+    @impl true
+    def init({executable, args}) do
+      Temp.track!()
+      path = Path.join(Temp.mkdir!(), "agent.sock")
+
+      children = [
+        Supervisor.child_spec({MuonTrap.Daemon, [executable, args ++ [path]]}, restart: :temporary, significant: true),
+        Supervisor.child_spec({Frajtano.Peer, {path, :spawned, {executable, args}}}, restart: :permanent)
+      ]
+
+      Supervisor.init(children, strategy: :one_for_all, auto_shutdown: :any_significant)
+    end
   end
 
-  def start_link(path) do
-    GenServer.start_link(__MODULE__, path, name: {:via, Registry, {Frajtano.Peers, path}})
+  def start({:socket, path}) do
+    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {__MODULE__, {path}})
+  end
+
+  def start({:spawn, spec}) do
+    DynamicSupervisor.start_child(Frajtano.PeerSupervisor, {Spawner, spec})
+  end
+
+  def start_link({path}) do
+    GenServer.start_link(__MODULE__, {path}, name: {:via, Registry, {Frajtano.Peers, path}})
+  end
+  def start_link({_, _, _} = spec) do
+    GenServer.start_link(__MODULE__, spec, name: {:via, Registry, {Frajtano.Peers, spec}})
   end
 
   @impl true
-  def init(path) do
+  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 init({path, :spawned, _}) do
+    if File.exists?(path) do
+      {:ok, conn} = :gen_tcp.connect({:local, path}, 0, [:binary, active: :once])
+      {:ok, %{conn: conn, clients: :queue.new(), buffer: <<>>}}
+    else
+      Process.sleep(100)
+      init({path, :spawned, nil})
+    end
+  end
+
   def reply({client, ref}, msg) do
     send(client, {ref, msg})
   end