From 453daa817b37ac9b32f64efb41c12350207306fb Mon Sep 17 00:00:00 2001
From: Kodi Craft <kodi@kdcf.me>
Date: Tue, 1 Oct 2024 10:51:08 +0200
Subject: [PATCH] Implement part of chunk sending

---
 apps/amethyst/lib/apps/connection_handler.ex | 50 ++++++++++++++++++++
 apps/amethyst/lib/states/configuration.ex    |  5 +-
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/apps/amethyst/lib/apps/connection_handler.ex b/apps/amethyst/lib/apps/connection_handler.ex
index ac43cbe..d36a090 100644
--- a/apps/amethyst/lib/apps/connection_handler.ex
+++ b/apps/amethyst/lib/apps/connection_handler.ex
@@ -60,6 +60,39 @@ defmodule Amethyst.ConnectionHandler do
       {:set_version, newversion} ->
         Logger.debug("Switching to version #{newversion} from #{version}")
         loop(socket, connstate, newversion, state)
+      {:set_position, position} ->
+        Logger.debug("Updating client position to #{inspect(position)}")
+        prev_position = Map.get(state, :position)
+        state = Map.put(state, :position, position)
+        # If there was no prev position, we consider that we
+        # definitely moved
+        prev_cp = if prev_position == nil do nil else chunk_pos(elem(prev_position, 0), elem(prev_position, 1)) end
+        cp = chunk_pos(elem(position, 0), elem(position, 1))
+        if prev_cp != cp do
+          Logger.debug("Client entered new chunk #{inspect(cp)}")
+          # We changed chunk borders, update center chunk and begin sending new chunks
+          send(self(), {:send_packet, %{
+            packet_type: :set_center_chunk,
+            chunk_x: elem(cp, 0),
+            chunk_z: elem(cp, 1)
+          }})
+          # Figure out which new chunks are visible
+          prev_chunks =
+            if prev_cp == nil do
+              MapSet.new([])
+            else
+              MapSet.new(visible_chunks_from(elem(prev_cp, 0), elem(prev_cp, 1), Map.get(state, :view_distance, 16)))
+            end
+          chunks = MapSet.new(visible_chunks_from(elem(cp, 0), elem(cp, 1), Map.get(state, :view_distance, 16)))
+          new_chunks = MapSet.difference(chunks, prev_chunks)
+          # Process these chunks, we can process all chunks in parallel
+          Task.Supervisor.async_stream(state |> Map.get(:game) |> Map.get(:refs) |> Map.get(:task_supervisor),
+            new_chunks,
+            fn chunk -> process_chunk(chunk, state) end,
+            [ordered: false]
+          ) |> Stream.run()
+        end
+        loop(socket, connstate, version, state)
       {:send_packet, packet} ->
         Logger.debug("Sending packet #{inspect(packet)}")
         send_packet(socket, connstate, packet, version)
@@ -73,6 +106,23 @@ defmodule Amethyst.ConnectionHandler do
     end
   end
 
+  defp chunk_pos(x, z) do
+    {div(floor(x), 16), div(floor(z), 16)}
+  end
+
+  defp visible_chunks_from(x, z, view_distance) do
+    {cx, cz} = chunk_pos(x, z)
+    (cx - view_distance - 3 .. cx + view_distance + 3) |> Enum.flat_map(fn ix ->
+      (cz - view_distance - 3 .. cz + view_distance + 3) |> Enum.map(fn iz ->
+        {ix, iz}
+      end)
+    end)
+  end
+
+  defp process_chunk(_chunk, _state) do
+    # TODO: Actually ask the game for the desired chunk then send the packets.
+  end
+
   defp handle_packet(id, data, connstate, version, state) do
     try do
       packet = connstate.deserialize(id, version, data)
diff --git a/apps/amethyst/lib/states/configuration.ex b/apps/amethyst/lib/states/configuration.ex
index c4e99a9..7426b65 100644
--- a/apps/amethyst/lib/states/configuration.ex
+++ b/apps/amethyst/lib/states/configuration.ex
@@ -305,9 +305,10 @@ defmodule Amethyst.ConnectionState.Configuration do
         }})
         send(self(), {:send_packet, Amethyst.ConnectionState.Play.ge_start_waiting_for_level_chunks(767)})
         send(self(), {:send_packet, %{packet_type: :set_center_chunk,
-          chunk_x: div(x, 16),
-          chunk_y: div(z, 16)
+          chunk_x: div(floor(x), 16),
+          chunk_z: div(floor(z), 16)
         }})
+        send(self(), {:set_position, {x, y, z}})
         state
     end
   end