dummy impl lmao lol funny commit message xD

lib/p2p_chat/transport.ex

@@ -0,0 +1,114 @@
+defmodule P2pChat.Transport do
+  require Logger
+  import P2pChat.TransportProto
+  alias P2pChat.TransportProto.Messages, as: Messages
+  use GenServer
+
+  @uuid_namespace "8a6a64ee-1628-4fdb-b3fc-574ae5eb5797"
+
+  defstruct [:socket, :netid, :neighbors]
+
+  def start_link(args \\ []) do
+    GenServer.start_link(__MODULE__, args)
+  end
+
+  @impl true
+  def init(args) do
+    {:ok, socket} = open_listening_socket(args)
+    {:ok, hostname} = :net.gethostname()
+    netid = UUID.uuid5(@uuid_namespace, to_string(hostname))
+    initial_neighbors = Access.get(args, :initial_neighbors, %{})
+
+    {:ok,
+     %__MODULE__{
+       socket: socket,
+       netid: netid,
+       neighbors: initial_neighbors
+     }}
+  end
+
+  def open_listening_socket(args) do
+    port = Access.get(args, :port, 12345)
+    listen_options = [:binary, :inet]
+    Logger.info("Starting transport on port #{port}")
+    {:ok, socket} = :gen_udp.open(port, listen_options)
+    {:ok, socket}
+  end
+
+  @impl true
+  def handle_info({:udp, _socket, peer_ip, peer_port, payload}, state) do
+    msg = decode_message(payload)
+    Logger.debug("Received UDP message from #{:inet.ntoa(peer_ip)}@#{peer_port}: #{inspect(msg)}")
+
+    {_, state} = case msg do
+      %Messages.Hello{} -> __MODULE__.handle_cast({:add_neighbor, msg.netid, {peer_ip, peer_port}}, state)
+      _ -> throw(:unhandled_message)
+    end
+    
+    {:noreply, state}
+  end
+
+  @impl true
+  def handle_call(:get_netid, _from, state) do
+    {:reply, state.netid, state}
+  end
+
+  @impl true
+  def handle_call(:get_neighbors, _from, state) do
+    {:reply, state.neighbors, state}
+  end
+
+  @impl true
+  def handle_cast({:add_neighbor, netid, connector}, state) do
+    new_neighbors =
+      Map.update(state.neighbors, netid, MapSet.new([connector]), fn current_value ->
+        MapSet.put(current_value, connector)
+      end)
+
+    new_state = %__MODULE__{
+      socket: state.socket,
+      netid: state.netid,
+      neighbors: new_neighbors
+    }
+
+    {:noreply, new_state}
+  end
+
+  @impl true
+  def handle_cast(:inform_about_self, state) do
+    inform_msg =
+      encode_message(%Messages.Hello{
+        netid: state.netid
+      })
+
+    Enum.each(Map.keys(state.neighbors), fn i_netid ->
+      Enum.each(Map.get(state.neighbors, i_netid), fn i_connector ->
+        {i_addr, i_port} = i_connector
+        Logger.debug("Informing neighbor #{i_netid} at #{:inet.ntoa(i_addr)}@#{i_port} about self")
+
+        :gen_udp.send(state.socket, i_addr, i_port, inform_msg)
+      end)
+    end)
+
+    {:noreply, state}
+  end
+
+  #
+  # CLIENT API
+  # 
+  def get_netid(pid) do
+    GenServer.call(pid, :get_netid)
+  end
+
+  def get_neighbors(pid) do
+    GenServer.call(pid, :get_neighbors)
+  end
+
+  def add_neighbor(pid, netid, connector) do
+    GenServer.cast(pid, {:add_neighbor, netid, connector})
+  end
+
+  def inform_about_self(pid) do
+    GenServer.cast(pid, :inform_about_self)
+  end
+end

lib/p2p_chat/transport_proto.ex

@@ -0,0 +1,67 @@
+defmodule P2pChat.TransportProto do
+  defmodule Messages do
+    defmodule Hello do
+      defstruct [:netid]
+    end
+    
+    defmodule InformNeighbor do
+      defstruct [:netid, :addr, :port]
+    end
+
+    defmodule Goodbye do
+      defstruct []
+    end
+  end
+
+  #
+  # Public API
+  # 
+
+  def encode_message(%Messages.Hello{} = msg) do
+    [encode_version(), <<0x01::8>>, encode_string(msg.netid)]
+  end
+  
+  def encode_message(%Messages.InformNeighbor{} = msg) do
+    [encode_version(), <<0x02::8>>, encode_string(msg.netid), encode_ip_addr(msg.addr)]
+  end
+
+  def encode_message(%Messages.Goodbye{} = _msg) do
+    [encode_version(), <<0x03::8>>]
+  end
+
+  def decode_message(<<0x01::8, 0x01::8, payload::binary>>) do
+    <<netid_len::16, netid::size(netid_len)-binary>> = payload
+    %Messages.Hello{netid: netid}
+  end
+
+  def decode_message(<<0x01::8, 0x02::8, payload::binary>>) do
+    <<netid_len::16, netid::size(netid_len)-binary, addr_len::16, addr::size(addr_len)-binary>> = payload
+    %Messages.InformNeighbor{netid: netid, addr: addr}
+  end
+
+  def decode_message(<<0x01::8, 0x03::8>>) do
+    %Messages.Goodbye{}
+  end
+
+  def decode_message(<<0x01::8, _::binary>>), do: :error
+  def decode_message(<<_::binary>>), do: :error
+
+  #
+  # Private Utilities
+  # 
+
+  defp encode_version() do
+    <<0x01::8>>
+  end
+
+  defp encode_string(str) do
+    [<<byte_size(str)::16>>, str]
+  end
+
+  defp encode_ip_addr({a1, a2, a3, a4, a5, a6, a7, a8}) do
+    <<6::8, a1::8, a2::8, a3::8, a4::8, a5::8, a6::8, a7::8, a8::8>>
+  end
+  defp encode_ip_addr({a1, a2, a3, a4}) do
+    <<4::8, a1::8, a2::8, a3::8, a4::8>>
+  end
+end