Add a component system

src/system/src/main/java/chylex/hee/system/component/AbstractAwareComponent.kt

@@ -0,0 +1,8 @@
+package chylex.hee.system.component
+
+abstract class AbstractAwareComponent {
+	var entityComponents: EntityComponents? = null
+	
+	open fun onComponentAttached() {}
+	open fun onComponentDetached() {}
+}

src/system/src/main/java/chylex/hee/system/component/EntityComponents.kt

@@ -0,0 +1,56 @@
+package chylex.hee.system.component
+
+class EntityComponents {
+	private val mutableComponents = mutableListOf<Any>()
+	
+	val components: List<Any>
+		get() = mutableComponents
+	
+	fun attach(component: Any) {
+		require(!mutableComponents.contains(component)) { "[EntityComponents] component must not be registered twice" }
+		mutableComponents.add(component)
+		
+		if (component is AbstractAwareComponent) {
+			require(component.entityComponents === null) { "[EntityComponents] component must not be registered in two entities" }
+			component.entityComponents = this
+			component.onComponentAttached()
+		}
+	}
+	
+	fun detach(component: Any) {
+		if (!mutableComponents.remove(component)) {
+			return
+		}
+		
+		if (component is AbstractAwareComponent) {
+			require(component.entityComponents === this) { "[EntityComponents] component was not registered correctly" }
+			component.onComponentDetached()
+			component.entityComponents = null
+		}
+	}
+	
+	inline fun <reified T> on(f: T.() -> Unit) {
+		for(component in components) {
+			if (component is T) {
+				f(component)
+			}
+		}
+	}
+	
+	inline fun <reified T, U> handle(f: T.() -> U?): U? {
+		for(component in components) {
+			if (component is T) {
+				val result = f(component)
+				if (result != null) {
+					return result
+				}
+			}
+		}
+		
+		return null
+	}
+	
+	inline fun <reified T> list(): List<T> {
+		return components.filterIsInstance<T>()
+	}
+}

src/system/src/main/java/chylex/hee/system/component/general/SerializableComponent.kt

@@ -0,0 +1,20 @@
+package chylex.hee.system.component.general
+
+import chylex.hee.system.component.EntityComponents
+import chylex.hee.system.serialization.TagCompound
+import net.minecraftforge.common.util.INBTSerializable
+
+interface SerializableComponent : INBTSerializable<TagCompound> {
+	val serializationKey: String
+}
+
+fun EntityComponents.serializeTo(tag: TagCompound) {
+	this.on<SerializableComponent> {
+		require(!tag.contains(serializationKey)) { "[SerializableComponent] cannot serialize duplicate key: $serializationKey" }
+		tag.put(serializationKey, serializeNBT())
+	}
+}
+
+fun EntityComponents.deserializeFrom(tag: TagCompound) {
+	this.on<SerializableComponent> { deserializeNBT(tag.getCompound(serializationKey)) }
+}

src/system/src/main/java/chylex/hee/system/component/general/TickableComponent.kt

@@ -0,0 +1,19 @@
+package chylex.hee.system.component.general
+
+import chylex.hee.system.component.EntityComponents
+import net.minecraft.entity.Entity
+
+interface TickableComponent {
+	@JvmDefault fun tickClient() {}
+	@JvmDefault fun tickServer() {}
+}
+
+@JvmName("tickEntity")
+fun <T : Entity> EntityComponents.tick(entity: T) {
+	if (entity.world.isRemote) {
+		this.on(TickableComponent::tickClient)
+	}
+	else {
+		this.on(TickableComponent::tickServer)
+	}
+}