From 7d25c3e6762fa122245fb5e3328474f0d1e97326 Mon Sep 17 00:00:00 2001
From: Tangent Wantwight <tangent128@gmail.com>
Date: Tue, 23 Jan 2024 23:29:11 -0500
Subject: [PATCH] Tick source

---
 lib/tick.ts | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 lib/tick.ts

diff --git a/lib/tick.ts b/lib/tick.ts
new file mode 100644
index 0000000..9a2161a
--- /dev/null
+++ b/lib/tick.ts
@@ -0,0 +1,36 @@
+import { Cancel, Source } from "./source";
+
+export type PhysicsTick = ["physics"];
+export type RenderTick = ["render", number];
+
+export function tick(fps: number): Source<PhysicsTick | RenderTick> {
+  function tickSource(): PhysicsTick;
+  function tickSource(
+    callback: (tick: PhysicsTick | RenderTick) => void
+  ): Cancel;
+  function tickSource(callback?: (tick: PhysicsTick | RenderTick) => void) {
+    if (callback) {
+      let lastPhysicsTick: number = new Date().getTime();
+
+      const physicsInterval = setInterval(() => {
+        lastPhysicsTick = new Date().getTime();
+        callback(["physics"]);
+      }, 1000 / fps);
+
+      let animationFrame = requestAnimationFrame(function animationTick() {
+        const now = new Date().getTime();
+        callback(["render", now - lastPhysicsTick]);
+        animationFrame = requestAnimationFrame(animationTick);
+      });
+
+      return () => {
+        clearInterval(physicsInterval);
+        cancelAnimationFrame(animationFrame);
+      };
+    } else {
+      return ["physics"];
+    }
+  }
+
+  return tickSource;
+}