Implement tiled multiplayer city simulation and scaling stages

scripts/entities.test.ts

@@ -0,0 +1,21 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { create, fromBinary, toBinary } from '@bufbuild/protobuf';
+import { AgentSchema, DeltaSchema, ServerMessageSchema, SnapshotSchema } from '../client/generated/city_pb';
+import { EntityState } from '../client/entities';
+
+test('binary protocol and interpolation preserve AOI spawn, change and despawn', () => {
+  const state = new EntityState();
+  const agent = create(AgentSchema,{id:1,x:0,y:0});
+  const envelope = create(ServerMessageSchema,{body:{case:'snapshot',value:{tick:10n,entities:[agent]}}});
+  const decoded = fromBinary(ServerMessageSchema,toBinary(ServerMessageSchema,envelope));
+  assert.equal(decoded.body.case,'snapshot');
+  state.snapshot(create(SnapshotSchema,{tick:10n,entities:[agent]}),1000);
+  state.delta(create(DeltaSchema,{tick:12n,changed:[create(AgentSchema,{id:1,x:200,y:100})]}),1200);
+  assert.deepEqual(state.positions(1300),[{id:1,x:1,y:0.5}]);
+  state.delta(create(DeltaSchema,{tick:11n,despawned:[1]}),1300);
+  assert.equal(state.size,1);
+  state.delta(create(DeltaSchema,{tick:14n,despawned:[1],spawned:[create(AgentSchema,{id:2,x:400,y:0})]}),1400);
+  assert.deepEqual(state.positions(1500),[{id:2,x:4,y:0}]);
+  state.clear(); assert.equal(state.size,0);
+});