Custom Dialect Support

apps/blunt/lib/blunt/application.ex

@@ -0,0 +1,13 @@
+defmodule Blunt.Application do
+  @moduledoc false
+  use Application
+
+  def start(_type, _args) do
+    children = [
+      Blunt.Dialect.Registry
+    ]
+
+    opts = [strategy: :one_for_one, name: Blunt.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end

apps/blunt/lib/blunt/config.ex

@@ -75,16 +75,14 @@ defmodule Blunt.Config do
 
   @doc false
   def dispatch_strategy! do
-    :dispatch_strategy
-    |> get(DispatchStrategy.Default)
-    |> Behaviour.validate!(DispatchStrategy)
+    %Blunt.Dialect{dispatch_strategy: strategy} = Blunt.Dialect.Registry.get_dialect!()
+    strategy
   end
 
   @doc false
   def pipeline_resolver! do
-    :pipeline_resolver
-    |> get(PipelineResolver.Default)
-    |> Behaviour.validate!(PipelineResolver)
+    %Blunt.Dialect{pipeline_resolver: resolver} = Blunt.Dialect.Registry.get_dialect!()
+    resolver
   end
 
   def type_spec_provider do

apps/blunt/lib/blunt/dialect.ex

@@ -0,0 +1,34 @@
+defmodule Blunt.Dialect do
+  alias Blunt.Behaviour
+  @callback setup(opts :: list({atom(), any()})) :: t()
+
+  @type t :: %__MODULE__{
+          dispatch_strategy: module(),
+          pipeline_resolver: module() | nil,
+          opts: list({atom, any})
+        }
+
+  @enforce_keys [:dispatch_strategy]
+  defstruct [
+    :dispatch_strategy,
+    :pipeline_resolver,
+    opts: []
+  ]
+
+  def configured_dialect! do
+    {module, args} =
+      case Application.get_env(:blunt, :dialect) do
+        nil ->
+          {Blunt.Dialect.StockDialect, [[]]}
+
+        module when is_atom(module) ->
+          {module, [[]]}
+
+        {module, opts} when is_atom(module) and is_list(opts) ->
+          {module, opts}
+      end
+
+    Behaviour.validate!(module, __MODULE__)
+    apply(module, :setup, args)
+  end
+end

apps/blunt/lib/blunt/dialect/registry.ex

@@ -0,0 +1,48 @@
+defmodule Blunt.Dialect.Registry do
+  @moduledoc false
+
+  alias Blunt.Dialect
+  use GenServer
+
+  def start_link(_opts) do
+    GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
+  end
+
+  def get_dialect! do
+    :ets.first(__MODULE__)
+  end
+
+  def put_dialect(%Blunt.Dialect{} = dialect) do
+    GenServer.call(__MODULE__, {:put_dialect, dialect})
+  end
+
+  def restore_dialect do
+    GenServer.call(__MODULE__, :restore_dialect)
+  end
+
+  @impl true
+  def init(:ok) do
+    table = :ets.new(__MODULE__, [:named_table, read_concurrency: true])
+    table = put_configured_dialect!(table)
+    {:ok, table}
+  end
+
+  @impl true
+  def handle_call({:put_dialect, dialect}, _from, table) do
+    true = :ets.delete_all_objects(table)
+    true = :ets.insert(table, {dialect})
+    {:reply, :ok, table}
+  end
+
+  def handle_call(:restore_dialect, _from, table) do
+    table = put_configured_dialect!(table)
+    {:reply, :ok, table}
+  end
+
+  defp put_configured_dialect!(table) do
+    dialect = Dialect.configured_dialect!()
+    true = :ets.delete_all_objects(table)
+    true = :ets.insert(table, {dialect})
+    table
+  end
+end

apps/blunt/lib/blunt/dialect/stock_dialect.ex

@@ -0,0 +1,11 @@
+defmodule Blunt.Dialect.StockDialect do
+  @behaviour Blunt.Dialect
+
+  @impl true
+  def setup(_opts) do
+    %Blunt.Dialect{
+      dispatch_strategy: Blunt.DispatchStrategy.Default,
+      pipeline_resolver: Blunt.DispatchStrategy.PipelineResolver.Default
+    }
+  end
+end

apps/blunt/mix.exs

@@ -37,6 +37,7 @@ defmodule Blunt.MixProject do
   # Run "mix help compile.app" to learn about applications.
   def application do
     [
+      mod: {Blunt.Application, []},
       extra_applications: [:logger]
     ]
   end

apps/blunt/test/blunt/custom_dispatch_strategy_test.exs

@@ -2,13 +2,16 @@ defmodule Blunt.CustomDispatchStrategyTest do
   use ExUnit.Case, async: false
 
   alias Blunt.DispatchContext, as: Context
-  alias Blunt.{Command, DispatchStrategy, CustomDispatchStrategy}
+  alias Blunt.{Command, CustomDispatchStrategy}
 
   setup do
-    Application.put_env(:blunt, :dispatch_strategy, CustomDispatchStrategy)
+    Blunt.Dialect.Registry.put_dialect(%Blunt.Dialect{
+      dispatch_strategy: CustomDispatchStrategy,
+      pipeline_resolver: Blunt.DispatchStrategy.PipelineResolver.Default
+    })
 
     on_exit(fn ->
-      Application.put_env(:blunt, :dispatch_strategy, DispatchStrategy.Default)
+      Blunt.Dialect.Registry.restore_dialect()
     end)
   end
 

apps/blunt_commanded/.formatter.exs

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

apps/blunt_commanded/.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").
+blunt_commanded_dialect-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

apps/blunt_commanded/README.md

@@ -0,0 +1,21 @@
+# BluntCommandedDialect
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `blunt_commanded_dialect` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:blunt_commanded_dialect, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at <https://hexdocs.pm/blunt_commanded_dialect>.
+

apps/blunt_commanded/config/config.exs

@@ -0,0 +1,5 @@
+import Config
+
+if config_env() == :test do
+  import_config "test.exs"
+end

apps/blunt_commanded/config/test.exs

@@ -0,0 +1 @@
+import Config

apps/blunt_commanded/lib/blunt/commanded/command_enrichment.ex

@@ -0,0 +1,19 @@
+defmodule Blunt.Commanded.CommandEnrichment do
+  alias Blunt.DispatchStrategy.PipelineResolver
+
+  @behaviour PipelineResolver
+
+  @callback enrich(command :: struct(), context :: Blunt.DispatchContext.t()) :: struct()
+
+  @impl PipelineResolver
+  def resolve(:command, message_module) do
+    handler = message_module |> Module.concat(:Enrichment) |> to_string()
+    {:ok, String.to_existing_atom(handler)}
+  rescue
+    _ -> {:ok, Blunt.Commanded.CommandEnrichment.Default}
+  end
+
+  def resolve(_message_type, _message_module) do
+    {:ok, Blunt.Commanded.CommandEnrichment.Default}
+  end
+end

apps/blunt_commanded/lib/blunt/commanded/command_enrichment/default.ex

@@ -0,0 +1,5 @@
+defmodule Blunt.Commanded.CommandEnrichment.Default do
+  @behaviour Blunt.Commanded.CommandEnrichment
+
+  def enrich(command), do: command
+end

apps/blunt_commanded/lib/blunt/commanded/dialect.ex

@@ -0,0 +1,20 @@
+defmodule Blunt.Commanded.Dialect do
+  @moduledoc false
+  @behaviour Blunt.Dialect
+
+  def setup(opts) do
+    commanded_app = Keyword.fetch!(opts, :commanded_app)
+
+    %Blunt.Dialect{
+      dispatch_strategy: Blunt.Commanded.DispatchStrategy,
+      pipeline_resolver: Blunt.Commanded.CommandEnrichment,
+      opts: [
+        commanded_app: commanded_application
+      ]
+    }
+  end
+
+  def commanded_app!(%Blunt.Dialect{opts: opts}) do
+    Keyword.fetch!(opts, :commanded_app)
+  end
+end

apps/blunt_commanded/lib/blunt/commanded/dispatch_strategy.ex

@@ -0,0 +1,10 @@
+defmodule Blunt.Commanded.DispatchStrategy do
+  alias Blunt.Commanded.DispatchStrategy.CommandStrategy
+
+  @behaviour Blunt.DispatchStrategy
+
+  @impl true
+  def dispatch(%{message_type: :command} = context) do
+    CommandStrategy.dispatch(context)
+  end
+end

apps/blunt_commanded/lib/blunt/commanded/dispatch_strategy/command_strategy.ex

@@ -0,0 +1,65 @@
+defmodule Blunt.Commanded.DispatchStrategy.CommandStrategy do
+  alias Blunt.Commanded.Dialect, as: CommandedDialect
+  alias Blunt.{Dialect, DispatchContext, PipelineResolver}
+
+  @behaviour Blunt.DispatchStrategy
+
+  @impl true
+  def dispatch(%{message_type: :command} = context) do
+    %{message_module: message_module, message: command, opts: opts} = context
+
+    case DispatchContext.get_return(context) do
+      :command_context ->
+        {:ok, context}
+
+      :command ->
+        return_final(command, context)
+
+      _ ->
+        # fetch the currently configured Blunt dialect
+        dialect = Dialect.Registry.get_dialect!()
+        commanded_app = CommandedDialect.commanded_app!(dialect)
+
+        opts = Keyword.put(opts, :metadata, metadata_from_context(context))
+        enrichment = PipelineResolver.get_pipeline!(context, CommandEnrichment)
+
+        with {:ok, context} <- execute({enrichment, :enrich, [command, context]}, context) do
+          case commanded_app.dispatch(command, opts) do
+            {:ok, execution_result} ->
+              %{events: events} = execution_result
+
+              context =
+                context
+                |> DispatchContext.put_pipeline(:commanded, events)
+                |> DispatchContext.put_private(execution_result)
+
+              {:ok, context}
+
+            {:error, error} ->
+              {:error,
+               context
+               |> DispatchContext.put_error(error)
+               |> DispatchContext.put_pipeline(:commanded, {:error, error})}
+          end
+        end
+    end
+  end
+
+  def metadata_from_context(%{id: dispatch_id} = context) do
+    user = Map.get(context, :user, %{}) || %{}
+
+    options = DispatchContext.options_map(context)
+
+    context
+    |> Map.take([
+      :created_at,
+      :message,
+      :message_module,
+      :message_type,
+      :user_supplied_fields
+    ])
+    |> Map.merge(options)
+    |> Map.put(:dispatch_id, dispatch_id)
+    |> Map.put(:dispatched_at, DateTime.utc_now())
+  end
+end

apps/blunt_commanded/mix.exs

@@ -0,0 +1,36 @@
+defmodule BluntCommandedDialect.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :blunt_commanded_dialect,
+      version: "0.1.0",
+      build_path: "../../_build",
+      config_path: "../../config/config.exs",
+      deps_path: "../../deps",
+      lockfile: "../../mix.lock",
+      elixir: "~> 1.14",
+      start_permanent: Mix.env() == :prod,
+      deps: deps(),
+      elixirc_paths: elixirc_paths(Mix.env())
+    ]
+  end
+
+  defp elixirc_paths(:test), do: ["lib", "test/support"]
+  defp elixirc_paths(_), do: ["lib"]
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:blunt, in_umbrella: true},
+      {:commanded, "~> 1.4", only: :test}
+    ]
+  end
+end

apps/blunt_commanded/test/blunt_commanded_dialect_test.exs

@@ -0,0 +1,8 @@
+defmodule BluntCommandedDialectTest do
+  use ExUnit.Case
+  doctest BluntCommandedDialect
+
+  test "greets the world" do
+    assert BluntCommandedDialect.hello() == :world
+  end
+end