amethyst/lib/servers/configuration.ex

# Amethyst - An experimental Minecraft server written in Elixir.
# Copyright (C) 2024 KodiCraft
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

defmodule Amethyst.Server.Configuration do
  @moduledoc """
  This module contains the logic for the Configuration stage of the server.
  """
  require Logger
  use Amethyst.Server

  alias Amethyst.Minecraft.Read
  alias Amethyst.Minecraft.Write

  @impl true
  def init(state) do
    state
  end

  ## DESERIALIZATION
  @impl true
  # Client Information https://wiki.vg/Protocol#Client_Information
  def deserialize(0x00, data) do
    {[locale, view_dist, chat_mode, chat_colors, displayed_skin_parts, main_hand, text_filtering, allow_listing], ""} =
      Read.start(data) |> Read.string |> Read.byte |> Read.varint |> Read.bool |> Read.ubyte |> Read.varint |> Read.bool |> Read.bool |> Read.stop
    chat_mode = case chat_mode do
      0 -> :enabled
      1 -> :commands_only
      2 -> :hidden
      _ -> raise RuntimeError, "Unknown chat mode #{chat_mode}"
    end
    main_hand = case main_hand do
      0 -> :left
      1 -> :right
      _ -> raise RuntimeError, "Unknown main hand #{main_hand}"
    end
    {:client_information, locale, view_dist, chat_mode, chat_colors, displayed_skin_parts, main_hand, text_filtering, allow_listing}
  end
  # Cookie Response https://wiki.vg/Protocol#Cookie_Response_(configuration)
  def deserialize(0x01, data) do
    {[key, exists], rest} = Read.start(data) |> Read.string |> Read.bool |> Read.stop
    if exists do
      {[length], rest} = Read.start(rest) |> Read.varint |> Read.stop
      {[data], _} = Read.start(rest) |> Read.raw(length) |> Read.stop
      {:cookie_response, key, data}
    else
      {:cookie_response, key, nil}
    end
  end
  # Serverbound Plugin Message https://wiki.vg/Protocol#Serverbound_Plugin_Message_(configuration)
  def deserialize(0x02, data) do
    {[channel], rest} = Read.start(data) |> Read.string |> Read.stop
    {:serverbound_plugin_message, channel, rest}
  end
  # Acknowledge Finish Configuration https://wiki.vg/Protocol#Acknowledge_Finish_Configuration
  def deserialize(0x03, "") do
    {:acknowledge_finish_configuration}
  end
  # Serverbound Keep Alive https://wiki.vg/Protocol#Serverbound_Keep_Alive_(configuration)
  def deserialize(0x04, data) do
    {[id], ""} = Read.start(data) |> Read.long |> Read.stop
    {:serverbound_keep_alive, id}
  end
  # Pong https://wiki.vg/Protocol#Pong_(configuration)
  def deserialize(0x05, data) do
    {[id], ""} = Read.start(data) |> Read.int |> Read.stop
    {:pong, id}
  end
  # Resource Pack Response https://wiki.vg/Protocol#Resource_Pack_Response_(configuration)
  def deserialize(0x06, data) do
    {[uuid, result], ""} = Read.start(data) |> Read.uuid |> Read.varint |> Read.stop
    result = case result do
      0 -> :successfully_downloaded
      1 -> :declined
      2 -> :failed_to_download
      3 -> :accepted
      4 -> :downloaded
      5 -> :invalid_url
      6 -> :failed_to_reload
      7 -> :discarded
      _ -> raise RuntimeError, "Unknown resource pack response #{result}"
    end
    {:resource_pack_response, uuid, result}
  end
  # Serverbound Known Packs https://wiki.vg/Protocol#Serverbound_Known_Packs
  def deserialize(0x07, data) do
    {[count], rest} = Read.start(data) |> Read.varint |> Read.stop
    {packs, _} = Enum.reduce(1..count, {[], rest}, fn _, {acc, rest} ->
      {[namespace, id, version], rest} = Read.start(rest) |> Read.string |> Read.string |> Read.string |> Read.stop
      {[{namespace, id, version} | acc], rest}
    end)
    {:serverbound_known_packs, packs}
  end
  def deserialize(type, _) do
    raise RuntimeError, "Got unknown packet type #{type}!"
  end

  ## SERIALIZATION
  @impl true
  # Cookie Request https://wiki.vg/Protocol#Cookie_Request_(configuration)
  def serialize({:cookie_request, id}) do
    Write.varint(0x00) <> Write.string(id)
  end
  # Clientbound Plugin Message https://wiki.vg/Protocol#Clientbound_Plugin_Message_(configuration)
  def serialize({:clientbound_plugin_message, channel, data}) do
    Write.varint(0x01) <> Write.string(channel) <> data
  end
  # Disconnect https://wiki.vg/Protocol#Disconnect_(configuration)
  def serialize({:disconnect, reason}) do
    Write.varint(0x02) <> Write.string(reason)
  end
  # Finish Configuration https://wiki.vg/Protocol#Finish_Configuration
  def serialize({:finish_configuration}) do
    Write.varint(0x03)
  end
  # Clientbound Keep Alive https://wiki.vg/Protocol#Clientbound_Keep_Alive_(configuration)
  def serialize({:clientbound_keep_alive, id}) do
    Write.varint(0x04) <> <<id::64-big-signed>>
  end
  # Ping https://wiki.vg/Protocol#Ping_(configuration)
  def serialize({:ping, id}) do
    Write.varint(0x05) <> <<id::32-big-signed>>
  end
  # Reset Chat https://wiki.vg/Protocol#Reset_Chat
  def serialize({:reset_chat}) do
    Write.varint(0x06)
  end
  # Registry Data https://wiki.vg/Protocol#Registry_Data
  def serialize({:registry_data, _id, _entries}) do
    raise ArgumentError, "Packet 'Registry Data' is not yet implemented"
  end
  # Remove Resource Pack https://wiki.vg/Protocol#Remove_Resource_Pack_(configuration)
  def serialize({:remove_resource_pack, id}) do
    Write.option(id, &Write.string/1)
  end
  # Add Resource Pack https://wiki.vg/Protocol#Add_Resource_Pack_(configuration)
  def serialize({:add_resource_pack, id, url, hash, forced, msg}) do
    Write.varint(0x09) <> Write.string(id) <> Write.string(url) <> Write.string(hash) <>
    Write.bool(forced) <> Write.option(msg, &Write.string/1)
  end
  # Store Cookie https://wiki.vg/Protocol#Store_Cookie_(configuration)
  def serialize({:store_cookie, id, data}) do
    Write.varint(0x0A) <> Write.string(id) <> Write.string(data)
  end
  # Transfer https://wiki.vg/Protocol#Transfer_(configuration)
  def serialize({:transfer, addr, port}) do
    Write.varint(0x0B) <> Write.string(addr) <> Write.varint(port)
  end
  # Feature Flags https://wiki.vg/Protocol#Feature_Flags
  def serialize({:feature_flags, flags}) do
    Write.varint(0x0C) <> Write.varint(length(flags)) <> Write.list(flags, &Write.string/1)
  end
  # Update Tags https://wiki.vg/Protocol#Update_Tags
  def serialize({:update_tags, tags}) do
    Write.varint(0x0D) <> Write.varint(length(tags)) <>
    Enum.reduce(tags, "", &serialize_tag/2)
  end
  # Clientbound Known Packs https://wiki.vg/Protocol#Clientbound_Known_Packs
  def serialize({:clientbound_known_packs, packs}) do
    Write.varint(0x0E) <> Write.varint(length(packs)) <>
    Write.list(packs, fn {namespace, id, version} -> Write.string(namespace) <> Write.string(id) <> Write.string(version) end)
  end
  # Custom Report Details https://wiki.vg/Protocol#Custom_Report_Details
  def serialize({:custom_report_details, details}) do
    Write.varint(0x0F) <> Write.varint(length(details)) <>
    Write.list(details, fn {id, data} -> Write.string(id) <> Write.string(data) end)
  end
  # Server Links https://wiki.vg/Protocol#Server_Links_(configuration)
  def serialize({:server_links, links}) do
    Write.varint(0x10) <> Write.varint(length(links)) <>
    Write.list(links, fn {label, url} -> serialize_link_label(label) <> Write.string(url) end)
  end
  def serialize(packet) do
    raise ArgumentError, "Tried serializing unknown packet #{inspect(packet)}"
  end

  defp serialize_tag({id, elements}, acc) do
    acc <> Write.string(id) <> Write.varint(length(elements)) <> serialize_elements(elements)
  end
  defp serialize_elements(elements) do
    Write.list(elements, fn {id, ids} ->
      Write.string(id) <> Write.varint(length(ids)) <>
      Write.list(ids, &Write.varint/1)
    end)
  end
  defp serialize_link_label(:bug_report) do
    <<0x01>> <> Write.varint(0x00)
  end
  defp serialize_link_label(:community_guidelines) do
    <<0x01>> <> Write.varint(0x01)
  end
  defp serialize_link_label(:support) do
    <<0x01>> <> Write.varint(0x02)
  end
  defp serialize_link_label(:status) do
    <<0x01>> <> Write.varint(0x03)
  end
  defp serialize_link_label(:feedback) do
    <<0x01>> <> Write.varint(0x04)
  end
  defp serialize_link_label(:community) do
    <<0x01>> <> Write.varint(0x05)
  end
  defp serialize_link_label(:website) do
    <<0x01>> <> Write.varint(0x06)
  end
  defp serialize_link_label(:forums) do
    <<0x01>> <> Write.varint(0x07)
  end
  defp serialize_link_label(:news) do
    <<0x01>> <> Write.varint(0x08)
  end
  defp serialize_link_label(:announcements) do
    <<0x01>> <> Write.varint(0x09)
  end
  defp serialize_link_label(other) do
    <<0x00>> <> Write.string(other)
  end

  ## HANDLING
  @impl true
  # Client Information https://wiki.vg/Protocol#Client_Information
  def handle({:client_information, locale, v_dist, chat_mode, chat_colors, displayed_skin_parts, main_hand, text_filtering, allow_listing}, client, state) do
    state = state |> Keyword.put(:locale, locale) |> Keyword.put(:view_dist, v_dist) |> Keyword.put(:chat_mode, chat_mode) |>
      Keyword.put(:chat_colors, chat_colors) |> Keyword.put(:displayed_skin_parts, displayed_skin_parts) |> Keyword.put(:main_hand, main_hand) |>
      Keyword.put(:text_filtering, text_filtering) |> Keyword.put(:allow_listing, allow_listing)
    # TODO: Here we should create the game handling task for this player and give it
    # this data.
    transmit({:clientbound_plugin_message, "minecraft:brand", Write.string("amethyst")}, client)
    transmit({:clientbound_known_packs, [{"minecraft", "core", "1.21"}]}, client)
    {:ok, state}
  end
  # Serverbound Known Packs https://wiki.vg/Protocol#Serverbound_Known_Packs
  def handle({:serverbound_known_packs, _packs}, client, state) do
    # L + ratio + don't care + didn't ask + finish configuration
    # TODO: we should send registries i think? does amethyst need to deal with vanilla registries at all? god only knows
    transmit({:finish_configuration}, client)
    {:ok, state}
  end
  # Acknowledge Finish Configuration https://wiki.vg/Protocol#Acknowledge_Finish_Configuration
  def handle({:acknowledge_finish_configuration}, client, state) do
    # TODO: All of this stuff should obviously not be hardcoded here
    Amethyst.Server.Play.transmit({:login,
      0, false, ["minecraft:overworld"], 0, 16, 16, false, true, true, 0,
      "minecraft:overworld", <<0::64>>, :spectator, nil, false, true, nil, 0, false
    }, client)
    Amethyst.Server.Play.serve(client, state)
  end
  # Serverbound Plugin Message https://wiki.vg/Protocol#Serverbound_Plugin_Message_(configuration)
  def handle({:serverbound_plugin_message, channel, data}, client, state) do
    handle_plugin_message(channel, data, client, state)
  end
  def handle(tuple, state) do
    Logger.error("Unhandled but known packet #{elem(tuple, 0)}")
    {:unhandled, state}
  end
  defp handle_plugin_message("minecraft:brand", data, _client, state) do
    {[brand], ""} = Read.start(data) |> Read.string |> Read.stop
    Logger.info("Client using brand: #{brand}")
    {:ok, Keyword.put(state, :brand, brand)}
  end
  defp handle_plugin_message("amethyst:hello", _data, _client, state) do
    Logger.info("Client is Amethyst aware! Hello!")
    {:ok, Keyword.put(state, :knows_amethyst, true)}
  end
end