From a8e5e723b7e1891c9b352261a3ee4c3d3563e8cf Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <me@liz.coffee>
Date: Sun, 26 Oct 2025 21:38:22 -0700
Subject: Checkpoint two

---
 .../commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt   | 29 ++++++++++------------
 1 file changed, 13 insertions(+), 16 deletions(-)

(limited to 'composeApp/src/commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt')

diff --git a/composeApp/src/commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt b/composeApp/src/commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt
index 77cb30b..c6303d3 100644
--- a/composeApp/src/commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt
+++ b/composeApp/src/commonMain/kotlin/coffee/liz/ecs/DAGWorld.kt
@@ -7,19 +7,20 @@ import kotlin.reflect.KClass
 import kotlin.time.Duration
 
 /**
- * [World] that updates in [System.dependencies] DAG order.
+ * [World] that updates in [System.dependencies] topological order.
  */
 @OptIn(ExperimentalAtomicApi::class)
-class DAGWorld<Outside>(systems: List<System<Outside>>) : World<Outside> {
+class DAGWorld<Outside>(
+    systems: List<System<Outside>>,
+) : World<Outside> {
     private val entities = mutableSetOf<Entity>()
     private val componentCache = mutableMapOf<KClass<out Component>, MutableSet<Entity>>()
     private val systemExecutionOrder: List<System<Outside>> = buildExecutionOrder(systems)
     private val nextEntityId = AtomicInt(0)
 
-    override fun createEntity(): Entity {
-        return Entity(nextEntityId.incrementAndFetch())
+    override fun createEntity(): Entity =
+        Entity(nextEntityId.incrementAndFetch())
             .also { entities.add(it) }
-    }
 
     override fun removeEntity(entity: Entity) {
         entity.componentTypes().forEach { componentType ->
@@ -31,17 +32,18 @@ class DAGWorld<Outside>(systems: List<System<Outside>>) : World<Outside> {
     override fun query(vararg componentTypes: KClass<out Component>): Set<Entity> {
         if (componentTypes.isEmpty()) return entities.toSet()
 
-        // Start with entities that have the first component type
         val firstType = componentTypes[0]
         val candidates = componentCache[firstType] ?: return emptySet()
 
-        // Filter to entities that have all component types
-        return candidates.filter { entity ->
-            componentTypes.all { entity.has(it) }
-        }.toSet()
+        return candidates
+            .filter { entity -> componentTypes.all { entity.has(it) } }
+            .toSet()
     }
 
-    override fun update(state: Outside, deltaTime: Duration) {
+    override fun update(
+        state: Outside,
+        deltaTime: Duration,
+    ) {
         refreshComponentCache()
         systemExecutionOrder.forEach { system ->
             system.update(this, state, deltaTime)
@@ -57,9 +59,6 @@ class DAGWorld<Outside>(systems: List<System<Outside>>) : World<Outside> {
         }
     }
 
-    /**
-     * Build a topologically sorted execution order from system dependencies.
-     */
     private fun buildExecutionOrder(systems: List<System<Outside>>): List<System<Outside>> {
         if (systems.isEmpty()) return emptyList()
 
@@ -88,7 +87,6 @@ class DAGWorld<Outside>(systems: List<System<Outside>>) : World<Outside> {
         val queue = ArrayDeque<KClass<out System<Outside>>>()
         val result = mutableListOf<System<Outside>>()
 
-        // Add all systems with no dependencies to queue
         queue.addAll(inDegree.filterValues { it == 0 }.keys)
 
         while (queue.isNotEmpty()) {
@@ -104,7 +102,6 @@ class DAGWorld<Outside>(systems: List<System<Outside>>) : World<Outside> {
             }
         }
 
-        // Check for cycles
         if (result.size != systems.size) {
             error("Circular dependency detected in systems")
         }
-- 
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