From 8d55357aadcac5f334919e7efa662b92e2a1ac2a Mon Sep 17 00:00:00 2001
From: cha0s <git@cha0s.io>
Date: Tue, 16 Apr 2019 14:04:11 -0500
Subject: [PATCH] refactor: World::tick heat off

---
 TODO.md                            |  2 +-
 packages/physics/abstract/world.js | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/TODO.md b/TODO.md
index ad7c92d..8f7ef6f 100644
--- a/TODO.md
+++ b/TODO.md
@@ -4,7 +4,7 @@
 - ❌ Synchronized should be a mixin
 - ❌ Behavior items should derive type/name
 - ✔ Precompile behavior traversals
-- ❌ Abstract physics world tick (hot position check, flat entity list)
+- ✔ Abstract physics world tick (hot position check, flat entity list)
 - ❌ Cache current routine for Behaved tick
 - ✔ Apply patches to matter.js
   ( https://github.com/liabru/matter-js/pulls?utf8=%E2%9C%93&q=is%3Apr+author%3Abchevalier )
diff --git a/packages/physics/abstract/world.js b/packages/physics/abstract/world.js
index c47c4e7..6bf4514 100644
--- a/packages/physics/abstract/world.js
+++ b/packages/physics/abstract/world.js
@@ -13,21 +13,34 @@ export class AbstractWorld extends decorate(class {}) {
   constructor() {
     super();
     this.entities = new Map();
+    this.entitiesList = [];
   }
 
   associateBodyWithEntity(body, entity) {
     this.entities.set(body, entity);
+    this.entitiesList.push(entity);
     body.position = entity.position;
   }
 
   removeBody(body) {
-    this.entities.delete(body);
+    if (this.entities.has(body)) {
+      const entity = this.entities.get(body);
+      this.entities.delete(body);
+      const index = this.entitiesList.indexOf(entity);
+      if (-1 !== index) {
+        this.entitiesList.splice(index, 1);
+      }
+    }
   }
 
   tick(elapsed) {
     // Propagate position updates.
-    for (const entity of this.entities.values()) {
-      if (Vector.equalsClose(entity.position, entity.body.position)) {
+    for (let i = 0; i < this.entitiesList.length; ++i) {
+      const entity = this.entitiesList[i];
+      const [entityX, entityY] = entity.position;
+      const [bodyX, bodyY] = entity.body.position;
+      // Hot.
+      if (entityX === bodyX && entityY === bodyY) {
         continue;
       }
       entity.position = entity.body.position;