Begin implementing GameCoordinator

apps/amethyst/lib/amethyst.ex

@@ -26,6 +26,7 @@ defmodule Amethyst.Application do
     children = [
       {Task.Supervisor, name: Amethyst.ConnectionSupervisor},
       {Amethyst.Keys, 1024},
+      {Amethyst.GameRegistry, []}
     ]
 
     children = case Application.fetch_env!(:amethyst, :port) do

apps/amethyst/lib/api/game.ex

@@ -0,0 +1,30 @@
+defmodule Amethyst.API.Game do
+  @moduledoc """
+  This module includes the interface for defining and registering
+  a game with Amethyst.
+  """
+  @callback instantiate() :: {:ok, new_state :: term} | {:error, reason :: term}
+
+  defmacro __using__(opts) do
+    meta = Keyword.get(opts, :meta, [])
+    quote do
+      @behaviour Amethyst.API.Game
+        def child_spec(state) do
+          %{
+            id: __MODULE__,
+            start: {__MODULE__, :start_link, []}
+          }
+        end
+        def start_link() do
+          register_self()
+          _loop()
+        end
+        defp _loop() do
+          _loop()
+        end
+        def register_self() do
+          Amethyst.GameRegistry.register(__MODULE__, unquote(meta))
+        end
+    end
+  end
+end

apps/amethyst/lib/apps/game_coordinator.ex

@@ -0,0 +1,36 @@
+defmodule Amethyst.GameCoordinator do
+  use GenServer
+
+  @moduledoc """
+  The game coordinator is responsible for keeping track of active
+  instances of each game and can create new ones on demand.
+  """
+
+  @impl true
+  def init(initial) do
+    {:ok, initial}
+  end
+
+  @impl true
+  def handle_call({:get, type}, _from, state) do
+    {:reply, find_or_create(type, state), state}
+  end
+
+  defp create(mod) do
+    state = mod.initialize()
+    spawn(mod, :listen, [state])
+  end
+
+  defp find(type, games) do
+    existing = games |> Enum.filter(fn {mod, _pid, _opts} -> mod == type end)
+    [{_mod, pid, _} | _] = existing
+    pid
+  end
+
+  defp find_or_create(type, games) do
+    case find(type, games) do
+      nil -> create(type)
+      some -> some
+    end
+  end
+end

apps/amethyst/lib/apps/game_registry.ex

@@ -0,0 +1,53 @@
+defmodule Amethyst.GameRegistry do
+  use GenServer
+
+  @moduledoc """
+  The game registry stores information about which games are
+  available.
+  """
+
+  @impl true
+  def init(initial) do
+    {:ok, initial}
+  end
+
+  @impl true
+  def handle_call({:register, module, meta}, _, state) do
+    if Keyword.get(meta, :default, false) && find_default(state) != nil do
+      {:reply, :error, :default_exists}
+    end
+    {:reply, :ok, [{module, meta} | state]}
+  end
+
+  @impl true
+  def handle_call({:list}, _, state) do
+    {:reply, state, state}
+  end
+
+  @impl true
+  def handle_call({:get_default}, _, state) do
+    {:reply, find_default(state), state}
+  end
+
+  defp find_default(state) do
+    state |> Enum.filter(fn {_mod, meta} ->
+      Keyword.get(meta, :default, false)
+    end) |> List.first(nil)
+  end
+
+  def start_link(initial) when is_list(initial) do
+    GenServer.start_link(__MODULE__, initial, name: {:global, __MODULE__})
+  end
+
+  def register(module, meta) do
+    GenServer.call({:global, __MODULE__}, {:register, module, meta})
+  end
+
+  def list() do
+    GenServer.call({:global, __MODULE__}, {:list})
+  end
+
+  def get_default() do
+    GenServer.call({:global, __MODULE__}, {:get_default})
+  end
+end

apps/amethyst/lib/servers/configuration.ex

@@ -332,6 +332,11 @@ defmodule Amethyst.Server.Configuration do
       0, false, ["minecraft:overworld"], 0, 16, 16, false, true, true, 0,
       "minecraft:overworld", <<0::64>>, :spectator, nil, false, true, nil, 0, false
     }, client)
+    game = Amethyst.GameRegistry.get_default()
+    if game == nil do
+      raise RuntimeError, "No game is set as a default! A single game must be defined as default for players to be able to join."
+    end
+    state = Keyword.put(state, :game, game)
     Amethyst.Server.Play.serve(client, state)
   end
   # Serverbound Plugin Message https://wiki.vg/Protocol#Serverbound_Plugin_Message_(configuration)

apps/example_game/.credo.exs

@@ -0,0 +1,188 @@
+%{
+  #
+  # You can have as many configs as you like in the `configs:` field.
+  configs: [
+    %{
+      #
+      # Run any config using `mix credo -C <name>`. If no config name is given
+      # "default" is used.
+      #
+      name: "default",
+      #
+      # These are the files included in the analysis:
+      files: %{
+        #
+        # You can give explicit globs or simply directories.
+        # In the latter case `**/*.{ex,exs}` will be used.
+        #
+        included: [
+          "lib/",
+          "src/",
+          "test/",
+        ],
+        excluded: [~r"/_build/", ~r"/deps/"]
+      },
+      plugins: [],
+      requires: [],
+      strict: false,
+      parse_timeout: 5000,
+      color: true,
+      #
+      # You can customize the parameters of any check by adding a second element
+      # to the tuple.
+      #
+      # To disable a check put `false` as second element:
+      #
+      #     {Credo.Check.Design.DuplicatedCode, false}
+      #
+      checks: %{
+        enabled: [
+          #
+          ## Consistency Checks
+          #
+          {Credo.Check.Consistency.ExceptionNames, []},
+          {Credo.Check.Consistency.LineEndings, []},
+          {Credo.Check.Consistency.ParameterPatternMatching, []},
+          {Credo.Check.Consistency.SpaceAroundOperators, []},
+          {Credo.Check.Consistency.SpaceInParentheses, []},
+          {Credo.Check.Consistency.TabsOrSpaces, []},
+
+          #
+          ## Design Checks
+          #
+          # You can customize the priority of any check
+          # Priority values are: `low, normal, high, higher`
+          #
+          {Credo.Check.Design.AliasUsage,
+           [priority: :low, if_nested_deeper_than: 2, if_called_more_often_than: 0]},
+          {Credo.Check.Design.TagFIXME, []},
+          # You can also customize the exit_status of each check.
+          # If you don't want TODO comments to cause `mix credo` to fail, just
+          # set this value to 0 (zero).
+          #
+          {Credo.Check.Design.TagTODO, [exit_status: 0]},
+
+          #
+          ## Readability Checks
+          #
+          {Credo.Check.Readability.AliasOrder, []},
+          {Credo.Check.Readability.FunctionNames, []},
+          {Credo.Check.Readability.LargeNumbers, []},
+          {Credo.Check.Readability.MaxLineLength, [priority: :low, max_length: 120]},
+          {Credo.Check.Readability.ModuleAttributeNames, []},
+          {Credo.Check.Readability.ModuleDoc, []},
+          {Credo.Check.Readability.ModuleNames, []},
+          {Credo.Check.Readability.ParenthesesInCondition, []},
+          {Credo.Check.Readability.ParenthesesOnZeroArityDefs, []},
+          {Credo.Check.Readability.PipeIntoAnonymousFunctions, []},
+          {Credo.Check.Readability.PredicateFunctionNames, []},
+          {Credo.Check.Readability.PreferImplicitTry, []},
+          {Credo.Check.Readability.RedundantBlankLines, []},
+          {Credo.Check.Readability.Semicolons, []},
+          {Credo.Check.Readability.SpaceAfterCommas, []},
+          {Credo.Check.Readability.StringSigils, []},
+          {Credo.Check.Readability.TrailingBlankLine, []},
+          {Credo.Check.Readability.TrailingWhiteSpace, []},
+          {Credo.Check.Readability.UnnecessaryAliasExpansion, []},
+          {Credo.Check.Readability.VariableNames, []},
+          {Credo.Check.Readability.WithSingleClause, []},
+
+          #
+          ## Refactoring Opportunities
+          #
+          {Credo.Check.Refactor.Apply, []},
+          {Credo.Check.Refactor.CondStatements, []},
+          {Credo.Check.Refactor.CyclomaticComplexity, []},
+          {Credo.Check.Refactor.FilterCount, []},
+          {Credo.Check.Refactor.FilterFilter, []},
+          {Credo.Check.Refactor.FunctionArity, []},
+          {Credo.Check.Refactor.LongQuoteBlocks, []},
+          {Credo.Check.Refactor.MapJoin, []},
+          {Credo.Check.Refactor.MatchInCondition, []},
+          {Credo.Check.Refactor.NegatedConditionsInUnless, []},
+          {Credo.Check.Refactor.NegatedConditionsWithElse, []},
+          {Credo.Check.Refactor.Nesting, []},
+          {Credo.Check.Refactor.RedundantWithClauseResult, []},
+          {Credo.Check.Refactor.RejectReject, []},
+          {Credo.Check.Refactor.UnlessWithElse, []},
+          {Credo.Check.Refactor.WithClauses, []},
+
+          #
+          ## Warnings
+          #
+          {Credo.Check.Warning.ApplicationConfigInModuleAttribute, []},
+          {Credo.Check.Warning.BoolOperationOnSameValues, []},
+          {Credo.Check.Warning.Dbg, []},
+          {Credo.Check.Warning.ExpensiveEmptyEnumCheck, []},
+          {Credo.Check.Warning.IExPry, []},
+          {Credo.Check.Warning.IoInspect, []},
+          {Credo.Check.Warning.MissedMetadataKeyInLoggerConfig, []},
+          {Credo.Check.Warning.OperationOnSameValues, []},
+          {Credo.Check.Warning.OperationWithConstantResult, []},
+          {Credo.Check.Warning.RaiseInsideRescue, []},
+          {Credo.Check.Warning.SpecWithStruct, []},
+          {Credo.Check.Warning.UnsafeExec, []},
+          {Credo.Check.Warning.UnusedEnumOperation, []},
+          {Credo.Check.Warning.UnusedFileOperation, []},
+          {Credo.Check.Warning.UnusedKeywordOperation, []},
+          {Credo.Check.Warning.UnusedListOperation, []},
+          {Credo.Check.Warning.UnusedPathOperation, []},
+          {Credo.Check.Warning.UnusedRegexOperation, []},
+          {Credo.Check.Warning.UnusedStringOperation, []},
+          {Credo.Check.Warning.UnusedTupleOperation, []},
+          {Credo.Check.Warning.WrongTestFileExtension, []}
+        ],
+        disabled: [
+          #
+          # Checks scheduled for next check update (opt-in for now)
+          {Credo.Check.Refactor.UtcNowTruncate, []},
+
+          #
+          # Controversial and experimental checks (opt-in, just move the check to `:enabled`
+          #   and be sure to use `mix credo --strict` to see low priority checks)
+          #
+          {Credo.Check.Consistency.MultiAliasImportRequireUse, []},
+          {Credo.Check.Consistency.UnusedVariableNames, []},
+          {Credo.Check.Design.DuplicatedCode, []},
+          {Credo.Check.Design.SkipTestWithoutComment, []},
+          {Credo.Check.Readability.AliasAs, []},
+          {Credo.Check.Readability.BlockPipe, []},
+          {Credo.Check.Readability.ImplTrue, []},
+          {Credo.Check.Readability.MultiAlias, []},
+          {Credo.Check.Readability.NestedFunctionCalls, []},
+          {Credo.Check.Readability.OneArityFunctionInPipe, []},
+          {Credo.Check.Readability.OnePipePerLine, []},
+          {Credo.Check.Readability.SeparateAliasRequire, []},
+          {Credo.Check.Readability.SingleFunctionToBlockPipe, []},
+          {Credo.Check.Readability.SinglePipe, []},
+          {Credo.Check.Readability.Specs, []},
+          {Credo.Check.Readability.StrictModuleLayout, []},
+          {Credo.Check.Readability.WithCustomTaggedTuple, []},
+          {Credo.Check.Refactor.ABCSize, []},
+          {Credo.Check.Refactor.AppendSingleItem, []},
+          {Credo.Check.Refactor.DoubleBooleanNegation, []},
+          {Credo.Check.Refactor.FilterReject, []},
+          {Credo.Check.Refactor.IoPuts, []},
+          {Credo.Check.Refactor.MapMap, []},
+          {Credo.Check.Refactor.ModuleDependencies, []},
+          {Credo.Check.Refactor.NegatedIsNil, []},
+          {Credo.Check.Refactor.PassAsyncInTestCases, []},
+          {Credo.Check.Refactor.PipeChainStart, []},
+          {Credo.Check.Refactor.RejectFilter, []},
+          {Credo.Check.Refactor.VariableRebinding, []},
+          {Credo.Check.Warning.LazyLogging, []},
+          {Credo.Check.Warning.LeakyEnvironment, []},
+          {Credo.Check.Warning.MapGetUnsafePass, []},
+          {Credo.Check.Warning.MixEnv, []},
+          {Credo.Check.Warning.UnsafeToAtom, []}
+
+          # {Credo.Check.Refactor.MapInto, []},
+
+          #
+          # Custom checks can be created using `mix credo.gen.check`.
+          #
+        ]
+      }
+    }
+  ]
+}

apps/example_game/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

apps/example_game/.gitignore

@@ -0,0 +1,26 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+example_game-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

apps/example_game/README.md

@@ -0,0 +1,3 @@
+# Example Game
+
+This module is a simple game which is made to aid in designing and testing Amethyst's APIs.

apps/example_game/lib/example/application.ex

@@ -0,0 +1,19 @@
+defmodule Example.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      {Example.Game, {}}
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: Example.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

apps/example_game/lib/example/game.ex

@@ -0,0 +1,8 @@
+defmodule Example.Game do
+  use Amethyst.API.Game, meta: [default: true]
+
+  @impl true
+  def instantiate() do
+    {:ok, [:hello]}
+  end
+end

apps/example_game/mix.exs

@@ -0,0 +1,32 @@
+defmodule Example.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :example_game,
+      version: "0.1.0",
+      build_path: "../../_build",
+      config_path: "../../config/config.exs",
+      deps_path: "../../deps",
+      lockfile: "../../mix.lock",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {Example.Application, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:amethyst, in_umbrella: true}
+    ]
+  end
+end

apps/example_game/test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()