Server actually ticks

2026-09-25 13:25:25 -03:00
parent 2a2ccae9ce
commit dfabe40e7a
18 changed files with 763 additions and 79 deletions
@@ -0,0 +1,116 @@
+import { assert, assertEquals } from "@std/assert";
+import { GameLoop, LoopClock } from "$/server/game/game_loop.ts";
+
+// a clock tests move by hand. ticks can move it too, to pretend they were slow
+class FakeClock implements LoopClock {
+	time = 0;
+	#timers: { at: number; fn: () => void; id: number }[] = [];
+	#next_id = 1;
+
+	now() {
+		return this.time;
+	}
+	schedule(fn: () => void, ms: number) {
+		const id = this.#next_id++;
+		this.#timers.push({ at: this.time + ms, fn, id });
+		return id;
+	}
+	clear(handle: unknown) {
+		this.#timers = this.#timers.filter((t) => t.id !== handle);
+	}
+	// runs timers in order until `ms` have passed
+	advance(ms: number) {
+		const end = this.time + ms;
+		while (true) {
+			this.#timers.sort((a, b) => a.at - b.at);
+			const timer = this.#timers[0];
+			if (!timer || timer.at > end) break;
+			this.#timers.shift();
+			this.time = Math.max(this.time, timer.at);
+			timer.fn();
+		}
+		this.time = end;
+	}
+}
+
+Deno.test("runs 20 ticks a second", () => {
+	const clock = new FakeClock();
+	let ticks = 0;
+	const loop = new GameLoop(() => ticks++, 20, clock);
+	loop.start();
+	clock.advance(10_000);
+	// the first tick runs right away
+	assertEquals(ticks, 201);
+	assertEquals(loop.stats.tps, 20);
+	loop.stop();
+	clock.advance(1000);
+	assertEquals(ticks, 201);
+});
+
+Deno.test("a slow tick is made up for, so game time keeps up", () => {
+	const clock = new FakeClock();
+	let ticks = 0;
+	const loop = new GameLoop(
+		() => {
+			ticks++;
+			// tick 10 takes 200 ms, four ticks' worth
+			if (ticks === 10) clock.time += 200;
+		},
+		20,
+		clock,
+	);
+	loop.start();
+	clock.advance(2000);
+	assertEquals(ticks, 41);
+	assertEquals(loop.stats.skipped, 0);
+});
+
+Deno.test("falling too far behind skips ticks and warns", () => {
+	const clock = new FakeClock();
+	const warnings: string[] = [];
+	const warn = console.warn;
+	console.warn = (message: string) => warnings.push(message);
+	try {
+		let ticks = 0;
+		const loop = new GameLoop(
+			() => {
+				ticks++;
+				// one 2 second hiccup, forty ticks' worth
+				if (ticks === 5) clock.time += 2000;
+			},
+			20,
+			clock,
+		);
+		loop.start();
+		clock.advance(5000);
+		// it catches up ten, skips the rest and carries on at 20 per second
+		assert(loop.stats.skipped >= 25 && loop.stats.skipped <= 31, `skipped ${loop.stats.skipped}`);
+		assertEquals(loop.stats.tps, 20);
+		assertEquals(warnings.length, 1);
+		assert(warnings[0].startsWith("Can't keep up"), warnings[0]);
+	} finally {
+		console.warn = warn;
+	}
+});
+
+Deno.test("a tick that throws doesn't stop the loop", () => {
+	const clock = new FakeClock();
+	let ticks = 0;
+	const error = console.error;
+	console.error = () => {};
+	try {
+		const loop = new GameLoop(
+			() => {
+				ticks++;
+				if (ticks === 3) throw new Error("oops");
+			},
+			20,
+			clock,
+		);
+		loop.start();
+		clock.advance(1000);
+		assertEquals(ticks, 21);
+	} finally {
+		console.error = error;
+	}
+});