From a9d774a43f01ea6346adc1d49a650a5bd145290d Mon Sep 17 00:00:00 2001
From: Evan Hemsley <2342303+ehemsley@users.noreply.github.com>
Date: Fri, 28 Jun 2019 22:07:48 -0700
Subject: [PATCH] add Spawner engine type

---
 encompass-cs/Engine.cs           |  6 ++--
 encompass-cs/Engines/Detector.cs |  2 +-
 encompass-cs/Engines/Spawner.cs  | 28 +++++++++++++++++++
 encompass-cs/WorldBuilder.cs     |  5 ++++
 test/SpawnerTest.cs              | 47 ++++++++++++++++++++++++++++++++
 5 files changed, 84 insertions(+), 4 deletions(-)
 create mode 100644 encompass-cs/Engines/Spawner.cs
 create mode 100644 test/SpawnerTest.cs

diff --git a/encompass-cs/Engine.cs b/encompass-cs/Engine.cs
index 80c9b30..2257b39 100644
--- a/encompass-cs/Engine.cs
+++ b/encompass-cs/Engine.cs
@@ -8,9 +8,9 @@ namespace Encompass
 {
     public abstract class Engine
     {
-        private readonly List<Type> mutateComponentTypes = new List<Type>();
-        private readonly List<Type> emitMessageTypes = new List<Type>();
-        private readonly List<Type> readMessageTypes = new List<Type>();
+        internal readonly List<Type> mutateComponentTypes = new List<Type>();
+        internal readonly List<Type> emitMessageTypes = new List<Type>();
+        internal readonly List<Type> readMessageTypes = new List<Type>();
 
         private EntityManager entityManager;
         private ComponentManager componentManager;
diff --git a/encompass-cs/Engines/Detector.cs b/encompass-cs/Engines/Detector.cs
index 4cbd64c..4ead6ac 100644
--- a/encompass-cs/Engines/Detector.cs
+++ b/encompass-cs/Engines/Detector.cs
@@ -12,7 +12,7 @@ namespace Encompass.Engines
 
         public IEnumerable<Type> ComponentTypes { get { return componentTypes; } }
 
-        protected Detector()
+        protected Detector() : base()
         {
             var detectsAttribute = GetType().GetCustomAttribute<Detects>(false);
             if (detectsAttribute != null)
diff --git a/encompass-cs/Engines/Spawner.cs b/encompass-cs/Engines/Spawner.cs
new file mode 100644
index 0000000..c91e4bf
--- /dev/null
+++ b/encompass-cs/Engines/Spawner.cs
@@ -0,0 +1,28 @@
+using System.Reflection;
+
+namespace Encompass.Engines
+{
+    public abstract class Spawner<TMessage> : Engine where TMessage : struct, IMessage
+    {
+        protected Spawner() : base()
+        {
+            var readsAttribute = GetType().GetCustomAttribute<Reads>(false);
+            if (readsAttribute != null)
+            {
+                readsAttribute.readMessageTypes.Add(typeof(TMessage));
+            }
+
+            readMessageTypes.Add(typeof(TMessage));
+        }
+
+        public override void Update(double dt)
+        {
+            foreach (var message in ReadMessages<TMessage>())
+            {
+                Spawn(message);
+            }
+        }
+
+        protected abstract void Spawn(TMessage message);
+    }
+}
diff --git a/encompass-cs/WorldBuilder.cs b/encompass-cs/WorldBuilder.cs
index 68f1560..1c18b9b 100644
--- a/encompass-cs/WorldBuilder.cs
+++ b/encompass-cs/WorldBuilder.cs
@@ -36,6 +36,11 @@ namespace Encompass
             return entityManager.CreateEntity();
         }
 
+        public void EmitMessage<TMessage>(TMessage message) where TMessage : struct, IMessage
+        {
+            messageManager.AddMessage(message);
+        }
+
         public Engine AddEngine<TEngine>(TEngine engine) where TEngine : Engine
         {
             engine.AssignEntityManager(entityManager);
diff --git a/test/SpawnerTest.cs b/test/SpawnerTest.cs
new file mode 100644
index 0000000..d4a3ce0
--- /dev/null
+++ b/test/SpawnerTest.cs
@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Encompass;
+using Encompass.Engines;
+using NUnit.Framework;
+
+namespace Tests
+{
+    public class SpawnerTest
+    {
+        struct TestComponent : IComponent { }
+        struct SpawnMessageA : IMessage { }
+
+        static Entity resultEntity;
+
+        class TestSpawner : Spawner<SpawnMessageA>
+        {
+            protected override void Spawn(SpawnMessageA message)
+            {
+                resultEntity = CreateEntity();
+                resultEntity.AddComponent(new TestComponent());
+            }
+        }
+
+        [Test]
+        public void RunsSpawnMethodOnMessageRead()
+        {
+            var worldBuilder = new WorldBuilder();
+            worldBuilder.AddEngine(new TestSpawner());
+
+            worldBuilder.EmitMessage(new SpawnMessageA());
+
+            var world = worldBuilder.Build();
+
+            world.Update(0.01);
+
+            Assert.That(resultEntity.HasComponent<TestComponent>(), Is.True);
+
+            var id = resultEntity.id;
+
+            world.Update(0.01);
+
+            Assert.That(resultEntity.id, Is.EqualTo(id));
+        }
+    }
+}