Begin implementing :set_player_position packet in Play

apps/amethyst/lib/api/game.ex

@@ -20,7 +20,8 @@ defmodule Amethyst.API.Game do
   a game with Amethyst.
   """
   @callback instantiate() :: {:ok, new_state :: term} | {:error, reason :: term}
-  @callback login(connection_process :: pid(), player_cfg :: keyword(), state :: term) :: {:ok, new_state :: term} | {:refuse, new_state :: term}
+  @callback login(from :: pid(), player_cfg :: keyword(), state :: term) :: {:ok, new_state :: term} | {:refuse, new_state :: term}
+  @callback player_position(from :: pid(), {x :: float(), y :: float(), z :: float()}, state :: term) :: {{x :: float(), y :: float(), z :: float()}, state :: term}
 
   defmacro __using__(opts) do
     meta = Keyword.get(opts, :meta, [])
@@ -54,6 +55,12 @@ defmodule Amethyst.API.Game do
             send(caller, :refuse)
             loop(mod, state)
         end
+      {:player_position, caller, pos} ->
+        case mod.player_position(caller, pos, state) do
+          {pos, state} ->
+            send(caller, pos)
+            loop(mod, state)
+        end
     end
   end
 
@@ -64,4 +71,12 @@ defmodule Amethyst.API.Game do
       :refuse -> :refuse
     end
   end
+
+  @spec player_position(atom() | pid() | port() | reference() | {atom(), atom()}, {float(), float(), float()}) :: {float(), float(), float()}
+  def player_position(pid, pos) do
+    send(pid, {:player_position, self(), pos})
+    receive do
+      pos -> pos
+    end
+  end
 end

apps/amethyst/lib/servers/play.ex

@@ -35,6 +35,26 @@ defmodule Amethyst.Server.Play do
     {[channel], data} = Read.start(data) |> Read.string |> Read.stop
     {:serverbound_plugin_message, channel, data}
   end
+  @impl true
+  def deserialize(0x1A, data) do
+    {[x, feet_y, z, on_ground], ""} = Read.start(data) |> Read.double |> Read.double |> Read.double |> Read.bool |> Read.stop
+    {:set_player_position, x, feet_y, z, on_ground}
+  end
+  @impl true
+  def deserialize(0x1B, data) do
+    {[x, feet_y, z, yaw, pitch, on_ground], ""} = Read.start(data) |> Read.double |> Read.double |> Read.double |> Read.float |> Read.float |> Read.bool |> Read.stop
+    {:set_position_position_and_rotation, x, feet_y, z, yaw, pitch, on_ground}
+  end
+  @impl true
+  def deserialize(0x1C, data) do
+    {[yaw, pitch, on_ground], ""} = Read.start(data) |> Read.float |> Read.float |> Read.bool |> Read.stop()
+    {:set_player_rotation, yaw, pitch, on_ground}
+  end
+  @impl true
+  def deserialize(0x1D, data) do
+    {[on_ground], ""} = Read.start(data) |> Read.bool |> Read.stop()
+    {:set_player_on_ground, on_ground}
+  end
   def deserialize(type, _) do
     raise RuntimeError, "Got unknown packet type #{type}!"
   end
@@ -80,8 +100,25 @@ defmodule Amethyst.Server.Play do
     Logger.debug("Got plugin message #{channel} with data #{inspect(data)}")
     {:ok, state}
   end
-  def handle(tuple, _, state) do
-    Logger.error("Unhandled but known packet #{elem(tuple, 0)}")
+  def handle({:set_player_position, x, y, z, _on_ground}, _client, state) do
+    # We do not accept movement packets until we get a :confirm_teleportation
+    if Keyword.fetch(state, :awaiting_tp_confirm) != :error do
+      Logger.warning("Got :set_player_position packet while waiting for :confirm_teleportation!")
+      {:ok, state}
+    else
+      game = Keyword.fetch!(state, :game)
+      {nx, ny, nz} = Amethyst.API.Game.player_position(game, {x, y, z})
+      # If pos is not very close to the position the client wants, synchronize them
+      # TODO: Make a general-purpose distance function
+      dist = :math.sqrt((nx - x)**2 + (ny - y)**2 + (nz - z)**2)
+      if dist > 0.01 do
+        # TODO: Implement synchronization
+        raise "The game wants to resynchronize the player, but I haven't implemented that yet"
+      end
+    end
+  end
+  def handle(tuple, _, state) do # TODO: These error cases should be somehow moved into some shared area? Maybe even moved out of the modules themselves
+    Logger.error("Unhandled but known packet #{inspect(tuple)}")
     {:unhandled, state}
   end