tolerate internet latency for initial inputs

packages/engine/src/networked-server.ts

@@ -91,7 +91,7 @@ export class NetworkedAuthoritativeEngine<
   ) {
     this.game = game;
     this.historyTicks = options.historyTicks ?? game.tickRateHz * 2;
-    this.maxPastTicks = options.maxPastTicks ?? 2;
+    this.maxPastTicks = options.maxPastTicks ?? game.tickRateHz;
     this.maxFutureTicks = options.maxFutureTicks ?? game.tickRateHz;
     this.snapshotEveryTicks = game.tickRateHz / game.snapshotRateHz;
     this.state = game.server.createInitialState();

packages/engine/src/server.ts

@@ -11,6 +11,10 @@ import type {
 
 export interface ServerEngineOptions {
   historyTicks?: number;
+  /**
+   * Maximum transport delay accepted for an input. Late inputs are applied on
+   * the next simulation step; they never rewrite authoritative history.
+   */
   maxPastTicks?: number;
   maxFutureTicks?: number;
 }
@@ -63,7 +67,7 @@ export class AuthoritativeEngine<State, Input> {
   ) {
     this.game = game;
     this.historyTicks = options.historyTicks ?? game.tickRateHz * 2;
-    this.maxPastTicks = options.maxPastTicks ?? 2;
+    this.maxPastTicks = options.maxPastTicks ?? game.tickRateHz;
     this.maxFutureTicks = options.maxFutureTicks ?? game.tickRateHz;
     this.snapshotEveryTicks = game.tickRateHz / game.snapshotRateHz;
     this.state = game.createInitialState();

packages/engine/test/engine.test.mjs

@@ -151,6 +151,34 @@ test("the developer-facing API compiles named sections into a networked game", (
   );
   server.step();
   assert.equal(server.currentState.value, 3);
+
+  // Internet clients can be several ticks behind the server when their first
+  // input arrives. Accept it within the default one-second transport window
+  // and apply it on the next authoritative step.
+  for (let index = 0; index < 6; index++) server.step();
+  assert.deepEqual(
+    server.submitInput(1, {
+      sequence: 2,
+      targetTick: 2,
+      observedTick: 2,
+      input: { amount: 2 },
+    }),
+    { accepted: true },
+  );
+  server.step();
+  assert.equal(server.currentState.value, 5);
+
+  for (let index = 0; index < 7; index++) server.step();
+  assert.deepEqual(
+    server.submitInput(1, {
+      sequence: 3,
+      targetTick: 2,
+      observedTick: 2,
+      input: { amount: 2 },
+    }),
+    { accepted: false, reason: "past" },
+  );
+
   assert.deepEqual(codec.decode(codec.encode({ unicode: "flux ⚡" })), {
     unicode: "flux ⚡",
   });