Delegate optional vars to optional configurations when building event…

… with the block

config/test.exs

@@ -1,4 +1,7 @@
 use Mix.Config
 
 config :event_bus,
-  topics: [:metrics_received, :metrics_summed]
+  topics: [:metrics_received, :metrics_summed],
+  ttl: 30_000_000,
+  time_unit: :micro_seconds,
+  id_generator: EventBus.Util.String

lib/event_bus/event_source.ex

@@ -12,6 +12,13 @@ defmodule EventBus.EventSource do
 
       alias EventBus.EventSource
       alias EventBus.Model.Event
+      alias EventBus.Util.String, as: StringUtil
+
+      @eb_app :event_bus
+      @eb_id_gen Application.get_env(@eb_app, :id_generator, StringUtil)
+      @eb_source String.replace("#{__MODULE__}", "Elixir.", "")
+      @eb_time_unit Application.get_env(@eb_app, :time_unit, :micro_seconds)
+      @eb_ttl Application.get_env(@eb_app, :ttl)
     end
   end
 
@@ -21,13 +28,10 @@ defmodule EventBus.EventSource do
   """
   defmacro build(params, do: yield) do
     quote do
-      started_at = System.monotonic_time(:micro_seconds)
-      initialized_at = System.os_time(:micro_seconds)
+      started_at = System.monotonic_time(@eb_time_unit)
+      initialized_at = System.os_time(@eb_time_unit)
       params = unquote(params)
 
-      source =
-        Map.get(params, :source, String.replace("#{__MODULE__}", "Elixir.", ""))
-
       {topic, data} =
         case unquote(yield) do
           {:error, error} ->
@@ -37,17 +41,17 @@ defmodule EventBus.EventSource do
             {params[:topic], result}
         end
 
-      time_spent = System.monotonic_time(:micro_seconds) - started_at
+      time_spent = System.monotonic_time(@eb_time_unit) - started_at
 
       %Event{
-        id: params[:id],
+        id: Map.get(params, :id, @eb_id_gen.unique_id()),
         topic: topic,
-        transaction_id: params[:transaction_id],
+        transaction_id: Map.get(params, :transaction_id),
         data: data,
         initialized_at: initialized_at,
         occurred_at: initialized_at + time_spent,
-        source: source,
-        ttl: params[:ttl]
+        source: Map.get(params, :source, @eb_source),
+        ttl: Map.get(params, :ttl, @eb_ttl)
       }
     end
   end

test/event_bus/event_source_test.exs

@@ -9,7 +9,7 @@ defmodule EventBus.EventSourceTest do
     :ok
   end
 
-  test "build with source" do
+  test "build with all params" do
     id = 1
     topic = :user_created
     data = %{id: 1, name: "me", email: "me@example.com"}
@@ -35,33 +35,37 @@ defmodule EventBus.EventSourceTest do
     assert event.source == "me"
     refute is_nil(event.initialized_at)
     refute is_nil(event.occurred_at)
+    assert Event.duration(event) > 0
   end
 
-  test "build without source" do
-    id = 1
+  test "build without passing source" do
     topic = :user_created
-    data = %{id: 1, name: "me", email: "me@example.com"}
-    transaction_id = "t1"
-    ttl = 100
-
     event =
-      EventSource.build %{
-        id: id,
-        topic: topic,
-        transaction_id: transaction_id,
-        ttl: ttl
-      } do
-        data
+      EventSource.build %{topic: topic} do
+        "some event data"
       end
 
-    assert event.data == data
-    assert event.id == id
-    assert event.topic == topic
-    assert event.transaction_id == transaction_id
-    assert event.ttl == ttl
     assert event.source == "EventBus.EventSourceTest"
-    refute is_nil(event.initialized_at)
-    refute is_nil(event.occurred_at)
+  end
+
+  test "build without passing ttl, sets the ttl from app configuration" do
+    topic = :user_created
+    event =
+      EventSource.build %{topic: topic} do
+        "some event data"
+      end
+
+    assert event.ttl == 30_000_000
+  end
+
+  test "build without passing id, sets the id with unique_id function" do
+    topic = :user_created
+    event =
+      EventSource.build %{topic: topic} do
+        "some event data"
+      end
+
+    refute is_nil(event.id)
   end
 
   test "build with error topic" do