refactor: auto component

eslint.config.js

@@ -0,0 +1,25 @@
+// eslint.config.js
+import globals from 'globals';
+import js from '@eslint/js';
+
+export default [
+  js.configs.recommended,
+  {
+    languageOptions: {
+      globals: {
+        ...globals.browser,
+        process: false,
+      },
+      parserOptions: {
+        ecmaFeatures: {
+          impliedStrict: true,
+          jsx: true
+        },
+      },
+    },
+    rules: {
+      // 'no-unused-vars': 'warn',
+      // 'no-undef': 'warn',
+    }
+  }
+];

package.json

@@ -14,6 +14,7 @@
   },
   "devDependencies": {
     "@chromatic-com/storybook": "^1.4.0",
+    "@eslint/js": "^9.3.0",
     "@storybook/addon-essentials": "^8.1.3",
     "@storybook/addon-interactions": "^8.1.3",
     "@storybook/addon-links": "^8.1.3",
@@ -23,11 +24,16 @@
     "@storybook/react-vite": "^8.1.3",
     "@storybook/test": "^8.1.3",
     "@vitejs/plugin-react": "^4.3.0",
+    "@vitest/coverage-v8": "^1.6.0",
+    "eslint": "^9.3.0",
+    "globals": "^15.3.0",
     "prop-types": "^15.8.1",
     "storybook": "^8.1.3",
-    "vite": "^5.2.11"
+    "vite": "^5.2.11",
+    "vitest": "^1.6.0"
   },
   "dependencies": {
+    "@msgpack/msgpack": "^3.0.0-beta2",
     "@pixi/react": "^7.1.2",
     "pixi.js": "^8.1.5",
     "react": "^18.3.1",

src/cell.js

@@ -0,0 +1,10 @@
+import {Ecs} from './ecs/index.js';
+
+export default class Cell {
+  constructor() {
+    this.ecs = new Ecs();
+  }
+  tick(elapsed) {
+    this.ecs.tick(elapsed);
+  }
+}

src/components/dom.jsx

@@ -1,6 +1,6 @@
 import {useEffect, useRef, useState} from 'react';
 
-import {RESOLUTION} from '../constants';
+import {RESOLUTION} from '../constants.js';
 import styles from './dom.module.css';
 
 /**

src/components/hotbar.jsx

@@ -1,4 +1,4 @@
-import Slot from './slot';
+import Slot from './slot.jsx';
 
 import styles from './hotbar.module.css';
 

src/components/pixi.jsx

@@ -5,10 +5,12 @@ import {
 import {useContext, useEffect, useState} from 'react';
 
 import {RESOLUTION} from '../constants.js';
-import ClientContext from '../context/client';
+import ClientContext from '../context/client.js';
-import Entities from './entities';
+import Entities from './entities.jsx';
 import styles from './pixi.module.css';
 
+import {Ecs} from '../ecs/index.js';
+
 export default function Pixi() {
   const client = useContext(ClientContext);
   const [entities, setEntities] = useState([]);
@@ -21,7 +23,19 @@ export default function Pixi() {
           break;
         }
         case 'tick': {
-          setEntities(payload.entities);
+          const {buffer, byteLength, byteOffset} = payload.entities;
+          const view = new DataView(buffer, byteOffset, byteLength);
+          const ecs = new Ecs();
+          ecs.decode(view);
+          const entities = [];
+          for (const entity of ecs.entities) {
+            const {Position, Visible} = ecs.get(entity);
+            entities.push({
+              image: Visible.image,
+              position: [Position.x, Position.y],
+            })
+          }
+          setEntities(entities);
           break;
         }
         default:

src/components/silphius.jsx

@@ -1,8 +1,8 @@
 import {useEffect, useState} from 'react';
 
 import ClientContext from '../context/client.js';
-import Title from './title';
+import Title from './title.jsx';
-import Ui from './ui';
+import Ui from './ui.jsx';
 
 export default function Silphius() {
   const connectionTuple = useState();
@@ -15,10 +15,10 @@ export default function Silphius() {
       let Client;
       switch (connectionTuple[0]) {
         case 'local':
-          ({default: Client} = await import('../client/local.js'));
+          ({default: Client} = await import('../net/client/local.js'));
           break;
         case 'remote':
-          ({default: Client} = await import('../client/remote.js'));
+          ({default: Client} = await import('../net/client/remote.js'));
           break;
       }
       const client = new Client();

src/components/ui.jsx

@@ -1,21 +1,14 @@
 import {useContext, useEffect} from 'react';
 
 import addKeyListener from '../add-key-listener.js';
-import {RESOLUTION} from '../constants';
+import {ACTION_MAP, RESOLUTION} from '../constants.js';
-import ClientContext from '../context/client';
+import ClientContext from '../context/client.js';
-import Dom from './dom';
+import Dom from './dom.jsx';
-import Pixi from './pixi';
+import Pixi from './pixi.jsx';
 import styles from './ui.module.css';
 
 const ratio = RESOLUTION[0] / RESOLUTION[1];
 
-// Handle input.
-const ACTION_MAP = {
-  w: 'moveUp',
-  d: 'moveRight',
-  s: 'moveDown',
-  a: 'moveLeft',
-};
 const KEY_MAP = {
   keyDown: 1,
   keyUp: 0,

src/constants.js

@@ -2,3 +2,17 @@ export const RESOLUTION = [
   800,
   450,
 ];
+
+export const ACTION_MAP = {
+  w: 'moveUp',
+  d: 'moveRight',
+  s: 'moveDown',
+  a: 'moveLeft',
+};
+
+export const MOVE_MAP = {
+  'moveUp': 'up',
+  'moveRight': 'right',
+  'moveDown': 'down',
+  'moveLeft': 'left',
+};

src/ecs/bundle.js

@@ -0,0 +1,58 @@
+export default class Bundle {
+
+  Components = {};
+
+  constructor(Components) {
+    this.Components = this.constructor.Components.reduce(
+      (r, Component, i) => {
+        /* v8 ignore next 3 */
+        if (!Components[i]) {
+          throw new TypeError(`Bundle(): no such component '${Component}'`);
+        }
+        return {...r, [Component]: Components[i]};
+      },
+      {},
+    );
+  }
+
+  configure(configuration) {
+    return this.constructor.configure(configuration, this.Components);
+  }
+
+  static configure(configuration, Components) {
+    const result = {};
+    const entries = Object.entries(Components);
+    for (let i = 0; i < entries.length; i++) {
+      const [component] = entries[i];
+      result[component] = configuration[component];
+    }
+    return result;
+  }
+
+  static maybeNormalize(BundleLike) {
+    const normalized = this.normalize(BundleLike);
+    return normalized.prototype instanceof Bundle ? normalized : undefined;
+  }
+
+  static normalize(BundleLike) {
+    if (Array.isArray(BundleLike)) {
+      return class AdhocBundle extends Bundle {
+        static Components = BundleLike;
+      };
+    }
+    return BundleLike;
+  }
+
+  static select(entity, Components) {
+    const bundle = {};
+    for (const i in Components) {
+      bundle[i] = Components[i].get(entity);
+    }
+    return bundle;
+  }
+
+  select(entity) {
+    return this.constructor.select(entity, this.Components);
+  }
+
+}

src/ecs/chain.js

@@ -0,0 +1,107 @@
+import Ecs from './ecs.js';
+
+export default class Chain {
+
+  index = 0;
+
+  proposals = [];
+
+  constructor(init) {
+    this.addProposal({
+      ecs: new Ecs(init),
+      elapsed: 0,
+      index: this.index++,
+    });
+  }
+
+  addProposal(proposal) {
+    this.proposals.push({
+      at: Date.now(),
+      ...proposal,
+    });
+  }
+
+  get dirty() {
+    const it = this.proposals[Symbol.iterator]()
+    return {
+      [Symbol.iterator]() {
+        return this;
+      },
+      next: () => {
+        let result = it.next();
+        while (!result.done && !result.value?.ecs.$$dirty) {
+          result = it.next();
+        }
+        if (result.done) {
+          return {done: true, value: undefined};
+        }
+        return result;
+      },
+    };
+  }
+
+  get latest() {
+    return this.proposals[this.proposals.length - 1];
+  }
+
+  mutate(when, mutator) {
+    let walk = this.proposals.length - 1;
+    let index = -1;
+    while (walk > 0) {
+      if (this.proposals[walk].index === when.index) {
+        index = walk;
+        break;
+      }
+      walk -= 1;
+    }
+    if (-1 === index) {
+      mutator(new Error('too late'));
+      return false;
+    }
+    let mutated = false;
+    while (index < this.proposals.length) {
+      const {ecs: previous} = this.proposals[index];
+      // opt: not clone
+      this.proposals[index].ecs = this.proposals[index - 1].ecs.clone();
+      const {ecs, elapsed} = this.proposals[index];
+      ecs.setClean();
+      if (mutated) {
+        ecs.tick(elapsed);
+      }
+      else {
+        ecs.tick(when.offset);
+        mutator(undefined, ecs);
+        ecs.tick(elapsed - when.offset);
+        mutated = true;
+      }
+      // opt: not strings
+      let actuallyDirty = false;
+      for (const {id} of ecs.dirty) {
+        if (JSON.stringify(ecs.get(id)) !== JSON.stringify(previous.get(id))) {
+          actuallyDirty = true;
+          break;
+        }
+      }
+      if (!actuallyDirty) {
+        ecs.setClean();
+      }
+      index += 1;
+    }
+  }
+
+  tick(elapsed) {
+    // opt: not clone
+    const ecs = this.latest.ecs.clone();
+    ecs.tick(elapsed);
+    this.addProposal({
+      ecs,
+      elapsed,
+      index: this.index++,
+    });
+    if (10 === this.proposals.length) {
+      this.proposals.shift();
+    }
+  }
+
+}
+

src/ecs/chain.test.js

@@ -0,0 +1,127 @@
+import {expect, test} from 'vitest';
+
+import Chain from './chain.js';
+import System from './system.js';
+
+const Controlled = {
+  input: 'uint8',
+};
+
+const Position = {
+  x: 'float32',
+  y: 'float32',
+};
+
+const Velocity = {
+  x: 'float32',
+  y: 'float32',
+};
+
+class Physics extends System {
+
+  static queries() {
+    return {
+      default: ['Position', 'Velocity'],
+    };
+  }
+
+  tick(elapsed) {
+    for (const [position, velocity] of this.select('default')) {
+      position.x += velocity.x * elapsed;
+      position.y += velocity.y * elapsed;
+    }
+  }
+
+}
+
+class Controlling extends System {
+
+  static queries() {
+    return {
+      default: ['Controlled', 'Velocity'],
+    };
+  }
+
+  tick() {
+    for (const [controlled, velocity] of this.select('default')) {
+      velocity.y = controlled.input ? 10 : 0;
+    }
+  }
+
+}
+
+test('efficiently rewrites history', () => {
+  const chain = new Chain({Controlled, Position, Velocity});
+  const {ecs} = chain.proposals[0];
+  const [one, two] = ecs.createMany([
+    {Controlled: {input: 0}, Position: {x: 10, y: 10}, Velocity: {x: 0, y: 0}},
+    {Controlled: {input: 0}, Position: {x: 20, y: 10}, Velocity: {x: -5, y: 0}},
+  ]);
+  const {latest: first} = chain;
+  chain.latest.ecs.setClean();
+  ecs.addSystem(Controlling);
+  ecs.addSystem(Physics);
+  chain.tick(1);
+  const {latest: second} = chain;
+  chain.latest.ecs.setClean();
+  expect(chain.latest.ecs.get(two).Position.x)
+    .to.equal(15);
+  chain.tick(1);
+  const {latest: third} = chain;
+  chain.latest.ecs.setClean();
+  expect(chain.latest.ecs.get(two).Position.x)
+    .to.equal(10);
+  expect(Array.from(chain.dirty).length)
+    .to.equal(0);
+  chain.mutate(
+    {index: 1, offset: 0.25},
+    (error, ecs) => {
+      ecs.get(one).Controlled.input = 1;
+    },
+  );
+  expect(Array.from(chain.dirty).length)
+    .to.equal(2);
+  expect(chain.latest.ecs.get(one).Position.y)
+    .to.equal(27.5);
+  expect(Array.from(first.ecs.dirty).length)
+    .to.equal(0);
+  expect(Array.from(second.ecs.dirty).length)
+    .to.not.equal(0);
+  second.ecs.setClean();
+  chain.mutate(
+    {index: 2, offset: 0.5},
+    (error, ecs) => {
+      ecs.get(one).Controlled.input = 0;
+    },
+  );
+  expect(Array.from(chain.dirty).length)
+    .to.equal(1);
+  expect(chain.latest.ecs.get(one).Position.y)
+    .to.equal(22.5);
+  expect(Array.from(chain.dirty).length)
+    .to.equal(1);
+  third.ecs.setClean();
+  third.ecs.get(one).Position.y = 22.5;
+  chain.mutate(
+    {index: 2, offset: 0.5},
+    (error, ecs) => {
+      ecs.get(one).Controlled.input = 0;
+    },
+  );
+  expect(Array.from(chain.dirty).length)
+    .to.equal(0);
+});
+
+test('fails when out of range', () => {
+  const chain = new Chain({});
+  let error;
+  expect(chain.mutate(
+    {index: 0, offset: 0.25},
+    (error_) => {
+      error = error_;
+    },
+  ))
+    .to.be.false;
+  expect(error)
+    .to.be.instanceOf(Error);
+});

src/ecs/component.js

@@ -0,0 +1,17 @@
+import Arbitrary from './component/arbitrary.js';
+import Flat from './component/flat.js';
+import Schema from './schema.js';
+
+function Component() {
+  const schema = new Schema(this.constructor.specification);
+  const Component = schema.size > 0
+    ? class extends Flat { static size = schema.size + 5; } // 5 = 1 for dirty + 4 for entity
+    : Arbitrary;
+  return new Component(schema);
+}
+
+export function createComponent(specification) {
+  return class AdhocComponent extends Component {
+    static specification = specification;
+  };
+}

src/ecs/component.test.js

@@ -0,0 +1,15 @@
+import {expect, test} from 'vitest';
+
+import {createComponent} from './component.js';
+
+test('creates flat components', () => {
+  const Component = createComponent({foo: {type: 'int32'}});
+  expect(new Component().schema.size)
+    .to.equal(4);
+});
+
+test('creates arbitrarily-sized components', () => {
+  const Component = createComponent({foo: {type: 'string'}});
+  expect(new Component().schema.size)
+    .to.equal(0);
+});

src/ecs/component/arbitrary.js

@@ -0,0 +1,123 @@
+import Serializer from '../serializer.js';
+
+import BaseComponent from './base.js';
+
+export default class ArbitraryComponent extends BaseComponent {
+
+  data = [];
+
+  serializer;
+
+  Instance;
+
+  constructor(schema) {
+    super(schema);
+    this.serializer = new Serializer(schema);
+  }
+
+  allocateMany(count) {
+    if (!this.Instance) {
+      this.Instance = this.instanceFromSchema();
+    }
+    const results = super.allocateMany(count);
+    count -= results.length; while (count--) {
+      results.push(this.data.push(new this.Instance()) - 1);
+    }
+    return results;
+  }
+
+  createMany(entries) {
+    if (entries.length > 0) {
+      const allocated = this.allocateMany(entries.length);
+      const {defaultValues} = this.schema;
+      const keys = Object.keys(this.schema.specification);
+      for (let i = 0; i < entries.length; ++i) {
+        const [entity, values = {}] = entries[i];
+        this.map[entity] = allocated[i];
+        this.data[allocated[i]].entity = entity;
+        if (false === values) {
+          continue;
+        }
+        for (let k = 0; k < keys.length; ++k) {
+          const j = keys[k];
+          if (j in values) {
+            this.data[allocated[i]][j] = values[j];
+          }
+          else if ('undefined' !== typeof defaultValues[j]) {
+            this.data[allocated[i]][j] = defaultValues[j];
+          }
+        }
+      }
+    }
+  }
+
+  decode(entity, view, offset) {
+    this.serializer.decode(view, this.get(entity), offset);
+  }
+
+  encode(entity, view, offset) {
+    this.serializer.encode(this.get(entity), view, offset);
+  }
+
+  get(entity) {
+    return this.data[this.map[entity]];
+  }
+
+  instanceFromSchema() {
+    const Component = this;
+    const Instance = class {
+      $$dirty = 1;
+      $$entity = 0;
+      toJSON() {
+        const json = {};
+        for (const [i] of Component.schema) {
+          json[i] = this[i];
+        }
+        return json;
+      }
+    };
+    const properties = {};
+    properties.dirty = {
+      get: function get() {
+        return !!this.$$dirty;
+      },
+      set: function set(v) {
+        this.$$dirty = v;
+      },
+    };
+    properties.entity = {
+      get: function get() {
+        return this.$$entity;
+      },
+      set: function set(v) {
+        this.$$entity = v;
+      },
+    };
+    for (const [i] of Component.schema) {
+      properties[i] = {
+        get: function get() {
+          return this[`$$${i}`];
+        },
+        set: function set(v) {
+          this[`$$${i}`] = v;
+          this.$$dirty = 1;
+          Component.setDirty(this.entity);
+        },
+      };
+    }
+    Object.defineProperties(Instance.prototype, properties);
+    return Instance;
+  }
+
+  setClean() {
+    /* v8 ignore next 3 */
+    if (!this.dirty) {
+      return;
+    }
+    super.setClean();
+    for (let i = 0; i < this.data.length; i++) {
+      this.data[i].dirty = false;
+    }
+  }
+
+}

src/ecs/component/arbitrary.test.js

@@ -0,0 +1,45 @@
+import {expect, test} from 'vitest';
+
+import Schema from '../schema.js';
+import Arbitrary from './arbitrary.js';
+
+const schema = new Schema({foo: {defaultValue: 'bar', type: 'string'}});
+
+test('creates instances', () => {
+  const Component = new Arbitrary(schema);
+  Component.create(1)
+  expect(Component.get(1).entity)
+    .to.equal(1);
+  expect(JSON.stringify(Component.get(1)))
+    .to.equal(JSON.stringify({foo: 'bar'}));
+  Component.create(2, {foo: 'baz'})
+  expect(JSON.stringify(Component.get(2)))
+    .to.equal(JSON.stringify({foo: 'baz'}));
+});
+
+test('manages dirty state', () => {
+  const Component = new Arbitrary(new Schema({foo: {type: 'string'}}));
+  Component.create(1);
+  Component.setClean();
+  expect(Component.get(1).dirty)
+    .to.be.false;
+  Component.get(1).foo = 'boo';
+  expect(Component.get(1).dirty)
+    .to.be.true;
+});
+
+test('reuses instances', () => {
+  const Component = new Arbitrary(new Schema({foo: {type: 'string'}}));
+  Component.create(1);
+  const instance = Component.get(1);
+  Component.destroy(1);
+  expect(Component.get(1))
+    .to.be.undefined;
+  expect(() => {
+    Component.destroy(1);
+  })
+    .to.throw();
+  Component.create(1);
+  expect(Component.get(1))
+    .to.equal(instance);
+});

src/ecs/component/base.js

@@ -0,0 +1,85 @@
+export default class BaseComponent {
+
+  $$dirty = true;
+
+  map = [];
+
+  pool = [];
+
+  schema;
+
+  constructor(schema) {
+    this.schema = schema;
+  }
+
+  allocateMany(count) {
+    const results = [];
+    while (count-- > 0 && this.pool.length > 0) {
+      results.push(this.pool.pop());
+    }
+    return results;
+  }
+
+  create(entity, values) {
+    this.createMany([[entity, values]]);
+  }
+
+  destroy(entity) {
+    this.destroyMany([entity]);
+  }
+
+  destroyMany(entities) {
+    this.freeMany(
+      entities
+        .map((entity) => {
+          if ('undefined' !== typeof this.map[entity]) {
+            return this.map[entity];
+          }
+          throw new Error(`can't free for non-existent entity ${entity}`);
+        }),
+    );
+    for (let i = 0; i < entities.length; i++) {
+      this.map[entities[i]] = undefined;
+    }
+  }
+
+  get dirty() {
+    return this.$$dirty;
+  }
+
+  freeMany(indices) {
+    for (let i = 0; i < indices.length; ++i) {
+      this.pool.push(indices[i]);
+    }
+  }
+
+  insertMany(entities) {
+    const creating = [];
+    for (let i = 0; i < entities.length; i++) {
+      const [entity, values] = entities[i];
+      if (!this.get(entity)) {
+        creating.push([entity, values]);
+      }
+      else {
+        this.set(entity, values);
+      }
+    }
+    this.createMany(creating);
+  }
+
+  set(entity, values) {
+    const instance = this.get(entity);
+    for (const i in values) {
+      instance[i] = values[i];
+    }
+  }
+
+  setClean() {
+    this.$$dirty = false;
+  }
+
+  setDirty() {
+    this.$$dirty = true;
+  }
+
+}

src/ecs/component/flat.js

@@ -0,0 +1,194 @@
+import BaseComponent from './base.js';
+import Schema from '../schema.js';
+
+export default class FlatComponent extends BaseComponent {
+
+  chunkSize = 64;
+
+  caret = 0;
+
+  data = new ArrayBuffer(0);
+
+  Window;
+
+  window;
+
+  allocateMany(count) {
+    const results = super.allocateMany(count);
+    count -= results.length;
+    if (count > 0) {
+      const required = (this.caret + count) * this.constructor.size;
+      if (required > this.data.byteLength) {
+        const chunkSize = this.chunkSize * this.constructor.size;
+        const remainder = required % chunkSize;
+        /* v8 ignore next */
+        const extra = 0 === remainder ? 0 : chunkSize - remainder;
+        const size = required + extra;
+        // soon...
+        const data = new ArrayBuffer(size);
+        (new Uint8Array(data)).set(this.data);
+        this.data = data;
+        this.Window = undefined;
+        this.window = undefined;
+      }
+      for (let i = 0; i < count; ++i) {
+        results.push(this.caret++);
+      }
+    }
+    return results;
+  }
+
+  createMany(entries) {
+    if (entries.length > 0) {
+      const allocated = this.allocateMany(entries.length);
+      /* v8 ignore next 3 */
+      if (!this.Window) {
+        this.Window = this.makeWindowClass();
+      }
+      const window = new this.Window(this.data, this);
+      const {defaultValues} = this.schema;
+      const keys = Object.keys(this.schema.specification);
+      for (let i = 0; i < entries.length; ++i) {
+        const [entity, values = {}] = entries[i];
+        this.map[entity] = allocated[i];
+        window.cursor = allocated[i] * this.constructor.size;
+        window.entity = entity;
+        if (false === values) {
+          continue;
+        }
+        for (let k = 0; k < keys.length; ++k) {
+          const j = keys[k];
+          if (j in values) {
+            window[j] = values[j];
+          }
+          else if ('undefined' !== typeof defaultValues[j]) {
+            window[j] = defaultValues[j];
+          }
+        }
+      }
+    }
+  }
+
+  decode(entity, view, offset) {
+    /* v8 ignore next 6 */
+    if (!this.Window) {
+      this.Window = this.makeWindowClass();
+    }
+    if (!this.window) {
+      this.window = new this.Window(this.data, this);
+    }
+    const cursor = this.map[entity] * this.constructor.size;
+    for (let i = 0; i < this.schema.size; ++i) {
+      this.window.view.setUint8(cursor + i, view.getUint8(offset + i));
+    }
+  }
+
+  encode(entity, view, offset) {
+    /* v8 ignore next 6 */
+    if (!this.Window) {
+      this.Window = this.makeWindowClass();
+    }
+    if (!this.window) {
+      this.window = new this.Window(this.data, this);
+    }
+    const cursor = this.map[entity] * this.constructor.size;
+    for (let i = 0; i < this.schema.size; ++i) {
+      view.setUint8(offset + i, this.window.view.getUint8(cursor + i));
+    }
+  }
+
+  get(entity) {
+    const offset = this.map[entity];
+    if (undefined === offset) {
+      return undefined;
+    }
+    /* v8 ignore next 6 */
+    if (!this.Window) {
+      this.Window = this.makeWindowClass();
+    }
+    if (!this.window) {
+      this.window = new this.Window(this.data, this);
+    }
+    this.window.cursor = offset * this.constructor.size;
+    return this.window;
+  }
+
+  makeWindowClass() {
+    const Component = this;
+    class Window {
+
+      cursor = 0;
+
+      parent;
+
+      view;
+
+      constructor(data, parent) {
+        if (data) {
+          this.view = new DataView(data);
+        }
+        if (parent) {
+          this.parent = parent;
+        }
+      }
+
+      toJSON() {
+        const json = {};
+        for (const [i] of Component.schema) {
+          json[i] = this[i];
+        }
+        return json;
+      }
+
+    }
+    let offset = 0;
+    const properties = {};
+    const {size} = this.constructor;
+    const get = (type) => (
+      `return this.view.get${Schema.viewMethodFromType(type)}(this.cursor + ${offset}, true);`
+    );
+    const set = (type) => [
+      `if (this.view.get${Schema.viewMethodFromType(type)}(this.cursor + ${offset}, true) === v) {`,
+      '  return;',
+      '}',
+      `this.parent.setDirty(this.view.getUint32(this.cursor + ${size - 5}, true));`,
+      `this.view.set${Schema.viewMethodFromType(type)}(this.cursor + ${offset}, v, true);`,
+      `this.view.setUint8(this.cursor + ${size - 1}, 1, true);`,
+    ].join('\n');
+    properties.dirty = {
+      get: new Function('', `return !!this.view.getUint8(this.cursor + ${size - 1}, true);`),
+      set: new Function('v', `this.view.setUint8(this.cursor + ${size - 1}, v ? 1 : 0, true);`),
+    };
+    properties.entity = {
+      get: new Function('', `return this.view.getUint32(this.cursor + ${size - 5}, true);`),
+      set: new Function('v', `this.view.setUint32(this.cursor + ${size - 5}, v, true);`),
+    };
+    for (const [i, spec] of this.schema) {
+      const {type} = spec;
+      properties[i] = {};
+      properties[i].get = new Function('', get(type));
+      properties[i].set = new Function('v', set(type));
+      offset += Schema.sizeOfType(type);
+    }
+    Object.defineProperties(Window.prototype, properties);
+    return Window;
+  }
+
+  setClean() {
+    /* v8 ignore next 3 */
+    if (!this.dirty) {
+      return;
+    }
+    super.setClean();
+    /* v8 ignore next 3 */
+    if (!this.Window) {
+      this.Window = this.makeWindowClass();
+    }
+    const window = new this.Window(this.data, this);
+    for (let i = 0; i < this.caret; ++i) {
+      window.dirty = false;
+      window.cursor += this.constructor.size;
+    }
+  }
+
+}

src/ecs/component/flat.test.js

@@ -0,0 +1,48 @@
+import {expect, test} from 'vitest';
+
+import Schema from '../schema.js';
+import Flat from './flat.js';
+
+const schema = new Schema({foo: {defaultValue: 42, type: 'uint8'}});
+
+class FixedSize extends Flat { static size = schema.size + 5; }
+
+test('creates instances', () => {
+  const Component = new FixedSize(schema);
+  Flat.size = 10;
+  Component.create(1)
+  expect(Component.get(1).entity)
+    .to.equal(1);
+  expect(Component.get(1).foo)
+    .to.equal(42);
+  Component.create(2, {foo: 12})
+  expect(Component.get(2).foo)
+    .to.equal(12);
+});
+
+test('manages dirty state', () => {
+  const Component = new FixedSize(schema);
+  Component.create(1);
+  Component.setClean();
+  expect(Component.get(1).dirty)
+    .to.be.false;
+  Component.get(1).foo = 'boo';
+  expect(Component.get(1).dirty)
+    .to.be.true;
+});
+
+test('reuses instances', () => {
+  const Component = new FixedSize(schema);
+  Component.create(1);
+  const instance = Component.get(1);
+  Component.destroy(1);
+  expect(Component.get(1))
+    .to.be.undefined;
+  expect(() => {
+    Component.destroy(1);
+  })
+    .to.throw();
+  Component.create(1);
+  expect(Component.get(1))
+    .to.equal(instance);
+});

src/ecs/components.js

@@ -0,0 +1,17 @@
+export const Controlled = {
+  up: 'float32',
+  right: 'float32',
+  down: 'float32',
+  left: 'float32',
+};
+
+export const Position = {
+  x: 'float32',
+  y: 'float32',
+};
+
+export const Visible = {
+  image: 'string',
+};
+
+export const Wandering = {};

src/ecs/ecs.js

@@ -0,0 +1,497 @@
+import Bundle from './bundle.js';
+import {createComponent} from './component.js';
+import EntityFactory from './entity-factory.js';
+import System from './system.js';
+
+export default class Ecs {
+
+  $$caret = 1;
+
+  $$dirty = false;
+
+  Bundles = {};
+
+  static ComponentLikesAndOrBundleLikes = {};
+
+  $$ComponentLikesAndOrBundleLikes;
+
+  Components = {};
+
+  $$entities = [];
+
+  $$entityFactory = new EntityFactory();
+
+  $$pool = [];
+
+  $$systems = [];
+
+  constructor() {
+    const {ComponentLikesAndOrBundleLikes} = this.constructor;
+    this.$$ComponentLikesAndOrBundleLikes = ComponentLikesAndOrBundleLikes;
+    const Bundles = [];
+    for (const i in ComponentLikesAndOrBundleLikes) {
+      const MaybeBundle = Bundle.maybeNormalize(ComponentLikesAndOrBundleLikes[i]);
+      if (MaybeBundle) {
+        Bundles.push([i, MaybeBundle]);
+      }
+      else {
+        this.Components[i] = this.withDirtyTracking(
+          createComponent(ComponentLikesAndOrBundleLikes[i]),
+        );
+      }
+    }
+    for (let i = 0; i < Bundles.length; i++) {
+      const [j, Bundle] = Bundles[i];
+      this.Bundles[j] = new Bundle(Bundle.Components.map((c) => this.Components[c]));
+    }
+  }
+
+  addSystem(source) {
+    const ecs = this;
+    class WrappedSystem extends System.normalize(source) {
+
+      constructor(Components) {
+        super(Components);
+        this.ecs = ecs;
+      }
+
+      createEntity(components) {
+        return this.ecs.create(components);
+      }
+
+      createManyEntities(componentsList) {
+        return this.ecs.createMany(componentsList);
+      }
+
+      get source() {
+        return source;
+      }
+
+      insertComponents(entity, components) {
+        this.ecs.insert(entity, components);
+      }
+
+      insertManyComponents(components) {
+        this.ecs.insertMany(components);
+      }
+
+      removeComponents(entity, components) {
+        this.ecs.remove(entity, components);
+      }
+
+      removeManyComponents(entities) {
+        this.ecs.removeMany(entities);
+      }
+
+    }
+    const wrappedSystem = new WrappedSystem(this.Components);
+    wrappedSystem.reindex(this.entities);
+    this.$$systems.push(wrappedSystem);
+  }
+
+  clone() {
+    const view = new DataView(new ArrayBuffer(this.sizeOf(this.entities)));
+    this.encode(this.entities, view);
+    const ecs = new this.constructor(this.$$ComponentLikesAndOrBundleLikes);
+    ecs.decode(view);
+    for (const system of this.$$systems) {
+      ecs.addSystem(system.source);
+    }
+    return ecs;
+  }
+
+  create(components = {}) {
+    const [entity] = this.createMany([components]);
+    return entity;
+  }
+
+  createExact(entity, components) {
+    this.createManyExact([[entity, components]]);
+  }
+
+  createMany(componentsList) {
+    const entities = [];
+    const creating = {};
+    for (let i = 0; i < componentsList.length; i++) {
+      const components = componentsList[i];
+      const componentKeys = [];
+      for (const key of Object.keys(components)) {
+        if (this.Components[key]) {
+          componentKeys.push(key);
+        }
+        const Bundle = this.Bundles[key];
+        if (Bundle) {
+          const configured = Bundle.configure(components[key]);
+          for (const subkey in configured) {
+            components[subkey] = configured[subkey];
+            componentKeys.push(subkey);
+          }
+        }
+      }
+      let entity;
+      if (this.$$pool.length > 0) {
+        entity = this.$$pool.pop();
+      }
+      else {
+        entity = this.$$caret++;
+      }
+      entities.push(entity);
+      this.rebuild(entity, () => componentKeys);
+      for (let j = 0; j < componentKeys.length; j++) {
+        const component = componentKeys[j];
+        if (!creating[component]) {
+          creating[component] = [];
+        }
+        creating[component].push([entity, components[component]]);
+      }
+    }
+    for (const i in creating) {
+      this.Components[i].createMany(creating[i]);
+    }
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].reindex(entities);
+    }
+    return entities;
+  }
+
+  createManyExact(entities) {
+    const creating = {};
+    for (const entry of entities) {
+      let components = {};
+      let entity;
+      if (Array.isArray(entry)) {
+        [entity, components = {}] = entry;
+      }
+      else {
+        entity = entry;
+      }
+      if (this.$$entities[entity]) {
+        throw new Error(`can't create existing entity ${entity}`);
+      }
+      const index = this.$$pool.indexOf(entity);
+      if (-1 !== index) {
+        this.$$pool.splice(index, 1);
+      }
+      this.rebuild(entity, () => Object.keys(components));
+      for (const j in components) {
+        if (!creating[j]) {
+          creating[j] = [];
+        }
+        creating[j].push([entity, components[j]]);
+      }
+    }
+    for (const i in creating) {
+      this.Components[i].createMany(creating[i]);
+    }
+  }
+
+  decode(view) {
+    let cursor = 0;
+    const count = view.getUint32(cursor, true);
+    if (0 === count) {
+      return;
+    }
+    const keys = Object.keys(this.Components);
+    cursor += 4;
+    const creating = new Map();
+    const updating = new Map();
+    const cursors = new Map();
+    for (let i = 0; i < count; ++i) {
+      const entity = view.getUint32(cursor, true);
+      if (!this.$$entities[entity]) {
+        creating.set(entity, {});
+      }
+      cursor += 4;
+      const componentCount = view.getUint16(cursor, true);
+      cursor += 2;
+      cursors.set(entity, {});
+      const addedComponents = [];
+      for (let j = 0; j < componentCount; ++j) {
+        const id = view.getUint16(cursor, true);
+        cursor += 2;
+        const component = keys[id];
+        if (!component) {
+          throw new Error(`can't decode component ${id}`);
+        }
+        if (!this.$$entities[entity]) {
+          creating.get(entity)[component] = false;
+        }
+        else if (!this.$$entities[entity].constructor.types.includes(component)) {
+          addedComponents.push(component);
+          if (!updating.has(component)) {
+            updating.set(component, []);
+          }
+          updating.get(component).push([entity, false]);
+        }
+        cursors.get(entity)[component] = cursor;
+        cursor += this.Components[component].schema.readSize(view, cursor);
+      }
+      if (addedComponents.length > 0 && this.$$entities[entity]) {
+        this.rebuild(entity, (types) => types.concat(addedComponents));
+      }
+    }
+    this.createManyExact(creating.entries());
+    for (const [component, entities] of updating) {
+      this.Components[component].createMany(entities);
+    }
+    for (const [entity, components] of cursors) {
+      for (const component in components) {
+        this.Components[component].decode(entity, view, components[component]);
+      }
+    }
+  }
+
+  destroy(entity) {
+    this.destroyMany([entity]);
+  }
+
+  destroyAll() {
+    this.destroyMany(this.entities);
+  }
+
+  destroyMany(entities) {
+    const destroying = {};
+    for (const entity of entities) {
+      if (!this.$$entities[entity]) {
+        throw new Error(`can't destroy non-existent entity ${entity}`);
+      }
+      for (const component of this.$$entities[entity].constructor.types) {
+        if (!destroying[component]) {
+          destroying[component] = [];
+        }
+        destroying[component].push(entity);
+      }
+      this.$$pool.push(entity);
+      this.$$entities[entity] = undefined;
+    }
+    for (const i in destroying) {
+      this.Components[i].destroyMany(destroying[i]);
+    }
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].deindex(entities);
+    }
+  }
+
+  get dirty() {
+    const ecs = this;
+    const it = this.$$entities[Symbol.iterator]()
+    return {
+      [Symbol.iterator]() {
+        return this;
+      },
+      next: () => {
+        if (!ecs.$$dirty) {
+          return {done: true, value: undefined};
+        }
+        let result = it.next();
+        while (!result.done && !result.value?.dirty) {
+          result = it.next();
+        }
+        if (result.done) {
+          return {done: true, value: undefined};
+        }
+        return result;
+      },
+    };
+  }
+
+  encode(entities, view, options = {}) {
+    const {onlyDirty = false} = options;
+    let cursor = 0;
+    let entitiesWritten = 0;
+    cursor += 4;
+    const keys = Object.keys(this.Components);
+    for (const entity of entities) {
+      if (onlyDirty && !this.$$entities[entity].dirty) {
+        continue;
+      }
+      entitiesWritten += 1;
+      view.setUint32(cursor, entity, true);
+      cursor += 4;
+      const entityComponents = this.$$entities[entity].constructor.types;
+      view.setUint16(cursor, entityComponents.length, true);
+      const componentsWrittenIndex = cursor;
+      cursor += 2;
+      if (0 === entityComponents.length) {
+        continue;
+      }
+      let componentsWritten = 0;
+      for (const component of entityComponents) {
+        const instance = this.Components[component];
+        if (onlyDirty && !instance.dirty) {
+          continue;
+        }
+        componentsWritten += 1;
+        view.setUint16(cursor, keys.indexOf(component), true);
+        cursor += 2;
+        const source = instance.get(entity);
+        this.Components[component].encode(entity, view, cursor);
+        cursor += instance.schema.sizeOf(source);
+      }
+      view.setUint16(componentsWrittenIndex, componentsWritten, true);
+    }
+    view.setUint32(0, entitiesWritten, true);
+  }
+
+  get entities() {
+    const it = this.$$entities[Symbol.iterator]()
+    return {
+      [Symbol.iterator]() {
+        return this;
+      },
+      next: () => {
+        let result = it.next();
+        while (!result.done && !result.value) {
+          result = it.next();
+        }
+        if (result.done) {
+          return {done: true, value: undefined};
+        }
+        return {done: false, value: result.value.id};
+      },
+    };
+  }
+
+  get(entity) {
+    return this.$$entities[entity];
+  }
+
+  insert(entity, components) {
+    this.insertMany([[entity, components]]);
+  }
+
+  insertMany(entities) {
+    const inserting = {};
+    const unique = new Set();
+    for (const [entity, components] of entities) {
+      this.rebuild(entity, (types) => [...new Set(types.concat(Object.keys(components)))]);
+      for (const component in components) {
+        if (!inserting[component]) {
+          inserting[component] = [];
+        }
+        inserting[component].push([entity, components[component]]);
+      }
+      unique.add(entity);
+    }
+    for (const component in inserting) {
+      this.Components[component].insertMany(inserting[component]);
+    }
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].reindex(unique.values());
+    }
+  }
+
+  rebuild(entity, types) {
+    let existing = [];
+    if (this.$$entities[entity]) {
+      existing.push(...this.$$entities[entity].constructor.types);
+    }
+    const Class = this.$$entityFactory.makeClass(types(existing), this.Components);
+    this.$$entities[entity] = new Class(entity);
+  }
+
+  remove(entity, components) {
+    this.removeMany([[entity, components]]);
+  }
+
+  removeMany(entities) {
+    const removing = {};
+    const unique = new Set();
+    for (const [entity, components] of entities) {
+      unique.add(entity);
+      for (const component of components) {
+        if (!removing[component]) {
+          removing[component] = [];
+        }
+        removing[component].push(entity);
+      }
+      this.rebuild(entity, (types) => types.filter((type) => !components.includes(type)));
+    }
+    for (const component in removing) {
+      this.Components[component].destroyMany(removing[component]);
+    }
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].reindex(unique.values());
+    }
+  }
+
+  removeSystem(SystemLike) {
+    const index = this.$$systems.findIndex((system) => SystemLike === system.source);
+    if (-1 !== index) {
+      this.$$systems.splice(index, 1);
+    }
+  }
+
+  setClean() {
+    for (const i in this.Components) {
+      this.Components[i].setClean();
+    }
+    for (const entity in this.$$entities) {
+      if (this.$$entities[entity]) {
+        this.$$entities[entity].dirty = false;
+      }
+    }
+    this.$$dirty = false;
+  }
+
+  sizeOf(entities, options = {}) {
+    const {onlyDirty = false} = options;
+    let size = 0;
+    if (0 === entities.length) {
+      return size;
+    }
+    size += 4;
+    for (const entity of entities) {
+      if (!this.$$entities[entity]) {
+        throw new Error(`can't encode non-existent entity ${entity}`);
+      }
+      if (onlyDirty && !this.$$entities[entity].dirty) {
+        continue;
+      }
+      // Entity + # of components.
+      size += 4 + 2;
+      for (const component of this.$$entities[entity].constructor.types) {
+        const instance = this.Components[component];
+        if (onlyDirty && !instance.dirty) {
+          continue;
+        }
+        size += 2 + instance.schema.sizeOf(instance.get(entity));
+      }
+    }
+    return size;
+  }
+
+  tick(elapsed) {
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].tick(elapsed);
+    }
+    for (let i = 0; i < this.$$systems.length; i++) {
+      this.$$systems[i].finalize(elapsed);
+    }
+    this.tickDestruction();
+  }
+
+  tickDestruction() {
+    const unique = new Set();
+    for (let i = 0; i < this.$$systems.length; i++) {
+      for (let j = 0; j < this.$$systems[i].destroying.length; j++) {
+        unique.add(this.$$systems[i].destroying[j]);
+      }
+      this.$$systems[i].tickDestruction();
+    }
+    if (unique.size > 0) {
+      this.destroyMany(unique.values());
+    }
+  }
+
+  withDirtyTracking(Component) {
+    const component = new Component();
+    component.setDirty = (entity) => {
+      component.$$dirty = true;
+      this.$$dirty = true;
+      this.$$entities[entity].dirty = true;
+    };
+    return component;
+  }
+
+}

src/ecs/ecs.test.js

@@ -0,0 +1,426 @@
+import {expect, test} from 'vitest';
+
+import Bundle from './bundle';
+import Ecs from './ecs';
+import System from './system';
+
+const Empty = {};
+
+const Position = {
+  x: {type: 'int32', defaultValue: 32},
+  y: 'int32',
+  z: 'int32',
+};
+
+test('can add and remove systems at runtime', () => {
+  const ecs = new Ecs();
+  let oneCount = 0;
+  let twoCount = 0;
+  const oneSystem = () => {
+    oneCount++;
+  };
+  ecs.addSystem(oneSystem);
+  ecs.tick();
+  expect(oneCount)
+    .to.equal(1);
+  const twoSystem = () => {
+    twoCount++;
+  };
+  ecs.addSystem(twoSystem);
+  ecs.tick();
+  expect(oneCount)
+    .to.equal(2);
+  expect(twoCount)
+    .to.equal(1);
+  ecs.removeSystem(oneSystem);
+  ecs.tick();
+  expect(oneCount)
+    .to.equal(2);
+  expect(twoCount)
+    .to.equal(2);
+});
+
+test('fails trying to exact create already existing', () => {
+  const ecs = new Ecs();
+  ecs.createExact(1);
+  expect(() => {
+    ecs.createExact(1);
+  })
+    .to.throw();
+});
+
+test('reuses from pool', () => {
+  const ecs = new Ecs();
+  ecs.createExact(1);
+  ecs.destroy(1);
+  expect(ecs.$$pool.length)
+    .to.equal(1);
+  expect(ecs.create())
+    .to.equal(1);
+  expect(ecs.$$pool.length)
+    .to.equal(0);
+});
+
+test('cleans pool when exact creating a previously existing entity', () => {
+  const ecs = new Ecs();
+  ecs.createManyExact([1]);
+  ecs.destroy(1);
+  expect(ecs.$$pool.length)
+    .to.equal(1);
+  ecs.createExact(1);
+  expect(ecs.$$pool.length)
+    .to.equal(0);
+});
+
+test('can create entities with components', () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}, Position: {y: 420}});
+  expect(JSON.stringify(ecs.get(entity)))
+    .to.deep.equal(JSON.stringify({Empty: {}, Position: {x: 32, y: 420, z: 0}}));
+});
+
+test("can remove entities' components", () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}, Position: {y: 420}});
+  ecs.remove(entity, ['Position']);
+  expect(JSON.stringify(ecs.get(entity)))
+    .to.deep.equal(JSON.stringify({Empty: {}}));
+});
+
+test('gets entities', () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}, Position: {y: 420}});
+  expect(JSON.stringify(ecs.get(entity)))
+    .to.deep.equal(JSON.stringify({Empty: {}, Position: {x: 32, y: 420, z: 0}}));
+});
+
+test('destroys entities', () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}, Position: {y: 420}});
+  ecs.destroyAll();
+  expect(ecs.get(entity))
+    .to.be.undefined;
+  expect(() => {
+    ecs.destroy(entity);
+  })
+    .to.throw();
+});
+
+test('can insert components into entities', () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}});
+  ecs.insert(entity, {Position: {y: 420}});
+  expect(JSON.stringify(ecs.get(entity)))
+    .to.deep.equal(JSON.stringify({Empty: {}, Position: {x: 32, y: 420, z: 0}}));
+  ecs.insert(entity, {Position: {y: 69}});
+  expect(JSON.stringify(ecs.get(entity)))
+    .to.deep.equal(JSON.stringify({Empty: {}, Position: {x: 32, y: 69, z: 0}}));
+});
+
+test('can tick systems', () => {
+  const Momentum = {
+    x: 'int32',
+    y: 'int32',
+    z: 'int32',
+  };
+  const ecs = new Ecs({Momentum, Position});
+  class Physics extends System {
+
+    static queries() {
+      return {
+        default: ['Position', 'Momentum'],
+      };
+    }
+
+    tick(elapsed) {
+      for (const [position, momentum] of this.select('default')) {
+        position.x += momentum.x * elapsed;
+        position.y += momentum.y * elapsed;
+        position.z += momentum.z * elapsed;
+      }
+    }
+
+  }
+  ecs.addSystem(Physics);
+  const entity = ecs.create({Momentum: {}, Position: {y: 420}});
+  const position = JSON.stringify(ecs.get(entity).Position);
+  ecs.tick(1);
+  expect(JSON.stringify(ecs.get(entity).Position))
+    .to.deep.equal(position);
+  ecs.get(1).Momentum.y = 30;
+  ecs.tick(1);
+  expect(JSON.stringify(ecs.get(entity).Position))
+    .to.deep.equal(JSON.stringify({x: 32, y: 450, z: 0}));
+});
+
+test('can create many entities when ticking systems', () => {
+  const ecs = new Ecs();
+  class Spawn extends System {
+    tick() {
+      this.createManyEntities(Array.from({length: 5}).map(() => []));
+    }
+  }
+  ecs.addSystem(Spawn);
+  ecs.create();
+  expect(ecs.get(5))
+    .to.be.undefined;
+  ecs.tick(1);
+  expect(ecs.get(5))
+    .to.not.be.undefined;
+});
+
+test('can create entities when ticking systems', () => {
+  const ecs = new Ecs();
+  class Spawn extends System {
+    tick() {
+      this.createEntity();
+    }
+  }
+  ecs.addSystem(Spawn);
+  ecs.create();
+  expect(ecs.get(2))
+    .to.be.undefined;
+  ecs.tick(1);
+  expect(ecs.get(2))
+    .to.not.be.undefined;
+});
+
+test('can schedule entities to be deleted when ticking systems', () => {
+  const ecs = new Ecs();
+  let entity;
+  class Despawn extends System {
+
+    finalize() {
+      entity = ecs.get(1);
+    }
+
+    static queries() {
+      return {
+        default: ['Despawn'],
+      };
+    }
+
+    tick() {
+      this.destroyEntity(1);
+    }
+
+  }
+  ecs.addSystem(Despawn);
+  ecs.createExact(1);
+  ecs.tick(1);
+  expect(entity)
+    .to.not.be.undefined;
+  expect(ecs.get(1))
+    .to.be.undefined;
+});
+
+test('can add components to and remove components from entities when ticking systems', () => {
+  const Foo = {bar: 'uint8'};
+  const ecs = new Ecs({Foo});
+  let addLength, removeLength;
+  class AddComponent extends System {
+    static queries() {
+      return {
+        default: ['Foo'],
+      };
+    }
+    tick() {
+      this.insertComponents(1, {Foo: {}});
+    }
+    finalize() {
+      addLength = Array.from(this.select('default')).length;
+    }
+  }
+  class RemoveComponent extends System {
+    static queries() {
+      return {
+        default: ['Foo'],
+      };
+    }
+    tick() {
+      this.removeComponents(1, ['Foo']);
+    }
+    finalize() {
+      removeLength = Array.from(this.select('default')).length;
+    }
+  }
+  ecs.addSystem(AddComponent);
+  ecs.createExact(1);
+  ecs.tick(1);
+  expect(addLength)
+    .to.equal(1);
+  expect(ecs.get(1).Foo)
+    .to.not.be.undefined;
+  ecs.removeSystem(AddComponent);
+  ecs.addSystem(RemoveComponent);
+  ecs.tick(1);
+  expect(removeLength)
+    .to.equal(0);
+  expect(ecs.get(1).Foo)
+    .to.be.undefined;
+});
+
+test('can add many components to and remove many components from entities when ticking systems', () => {
+  const Foo = {bar: 'uint8'};
+  const ecs = new Ecs({Foo});
+  class AddComponent extends System {
+    tick() {
+      this.insertManyComponents([
+        [1, {Foo: {}}],
+        [2, {Foo: {bar: 42}}],
+      ]);
+    }
+  }
+  class RemoveComponent extends System {
+    tick() {
+      this.removeManyComponents([
+        [1, ['Foo']],
+        [2, ['Foo']],
+      ]);
+    }
+  }
+  ecs.addSystem(AddComponent);
+  ecs.createManyExact([1, 2]);
+  ecs.tick(1);
+  expect(ecs.get(2).Foo.bar)
+    .to.equal(42);
+  ecs.removeSystem(AddComponent);
+  ecs.addSystem(RemoveComponent);
+  ecs.tick(1);
+  expect(ecs.get(2).Foo)
+    .to.be.undefined;
+});
+
+test('can encode and decode an ecs', () => {
+  const ecs = new Ecs({Empty, Position});
+  const view = new DataView(new ArrayBuffer(1024));
+  expect(() => {
+    ecs.encode([], view);
+  })
+    .not.to.throw();
+  const entity = ecs.create({Empty: {}, Position: {y: 420}});
+  ecs.encode([entity], view, {onlyDirty: true});
+  const newEcs = new Ecs({Empty, Position});
+  newEcs.decode(view);
+  expect(JSON.stringify(newEcs.get(entity)))
+    .to.deep.equal(JSON.stringify(ecs.get(entity)));
+  ecs.setClean();
+  ecs.encode([entity], view, {onlyDirty: true});
+  const newEcs2 = new Ecs({Empty, Position});
+  newEcs2.decode(view);
+  expect(newEcs2.get(entity))
+    .to.be.undefined;
+  ecs.get(entity).Position.x = 42;
+  ecs.encode([entity], view, {onlyDirty: true});
+  newEcs2.decode(view);
+  expect(newEcs2.get(entity))
+    .to.not.be.undefined;
+  expect(newEcs2.get(entity).Empty)
+    .to.be.undefined;
+  ecs.encode([entity], view);
+  newEcs2.decode(view);
+  expect(newEcs2.get(entity))
+    .to.not.be.undefined;
+  const empty = newEcs2.get(entity).Empty;
+  expect(empty)
+    .to.not.be.undefined;
+  newEcs2.decode(view);
+  expect(empty)
+    .to.not.be.undefined;
+});
+
+test('catches bad encoding', () => {
+  const ecs = new Ecs({Empty, Position});
+  const entity = ecs.create({Empty: {}});
+  const view = new DataView(new ArrayBuffer(1024));
+  ecs.encode([entity], view);
+  view.setUint16(10, 2);
+  const newEcs = new Ecs({Empty, Position});
+  expect(() => {
+    newEcs.decode(view);
+  })
+    .to.throw();
+});
+
+test('manages dirtiness', () => {
+  const ecs = new Ecs({Position});
+  const entity = ecs.create({Position: {x: 42}});
+  expect(ecs.Components['Position'].dirty)
+    .to.be.true;
+  ecs.setClean();
+  expect(ecs.Components['Position'].dirty)
+    .to.be.false;
+  ecs.get(entity).Position.x = 13;
+  expect(ecs.Components['Position'].dirty)
+    .to.be.true;
+});
+
+test('handles empty size', () => {
+  const ecs = new Ecs({Empty, Position});
+  expect(ecs.sizeOf([]))
+    .to.equal(0);
+});
+
+test('catches non-existent size', () => {
+  const ecs = new Ecs({Empty, Position});
+  ecs.create({Empty: {}, Position: {x: 42}});
+  expect(() => {
+    ecs.sizeOf([2]);
+  })
+    .to.throw();
+});
+
+test('calculates size based on dirtiness', () => {
+  const ecs = new Ecs({Empty, Position});
+  const first = ecs.create({Empty: {}, Position: {x: 42}});
+  ecs.create({Empty: {}, Position: {y: 42}});
+  const sizeOfBoth = ecs.sizeOf([1, 2], true);
+  ecs.setClean();
+  ecs.get(first).Position.x = 13;
+  expect(ecs.sizeOf([1, 2], {onlyDirty: true}))
+    .to.be.lessThan(sizeOfBoth);
+  expect(ecs.sizeOf([1, 2]))
+    .to.equal(sizeOfBoth);
+});
+
+test('clones an ecs', () => {
+  const ecs = new Ecs({Position});
+  const entity = ecs.create({Position: {y: 420}});
+  const entity2 = ecs.create();
+  const newEcs = ecs.clone();
+  expect(JSON.stringify(newEcs.get(entity)))
+    .to.deep.equal(JSON.stringify(ecs.get(entity)));
+  expect(JSON.stringify(newEcs.get(entity2)))
+    .to.deep.equal(JSON.stringify(ecs.get(entity2)));
+});
+
+test('can add bundles', () => {
+  const Height = {height: 'uint32'};
+  const Width = {width: 'uint32'};
+  const Area = ['Height', 'Width'];
+  class ConfiguredArea extends Bundle {
+
+    static configure({height, width}) {
+      return {Height: {height}, Width: {width}};
+    }
+
+    static Components = ['Height', 'Width'];
+
+  }
+  const ecs = new Ecs({
+    Area,
+    ConfiguredArea,
+    Height,
+    Width,
+  });
+  const entity = ecs.get(ecs.create({Area: {Width: {width: 420}}}));
+  expect(entity.Height.height)
+    .to.equal(0);
+  expect(entity.Width.width)
+    .to.equal(420);
+  const configuredEntity = ecs.get(ecs.create({ConfiguredArea: {width: 420}}));
+  expect(configuredEntity.Height.height)
+    .to.equal(0);
+  expect(configuredEntity.Width.width)
+    .to.equal(420);
+});

src/ecs/entity-factory.js

@@ -0,0 +1,48 @@
+class Node {
+  children = {};
+  class;
+}
+
+export default class EntityFactory {
+
+  $$tries = new Node();
+
+  makeClass(types, Components) {
+    const sorted = types.toSorted();
+    let walk = this.$$tries;
+    let i = 0;
+    while (i < sorted.length) {
+      if (!walk.children[sorted[i]]) {
+        walk.children[sorted[i]] = new Node();
+      }
+      walk = walk.children[sorted[i]];
+      i += 1;
+    }
+    if (!walk.class) {
+      class Entity {
+        dirty = true;
+        static types = sorted;
+        constructor(id) {
+          this.id = id;
+        }
+      }
+      const properties = {};
+      for (const type of sorted) {
+        properties[type] = {};
+        const get = Components[type].get.bind(Components[type]);
+        properties[type].get = function() {
+          return get(this.id);
+        };
+      }
+      Object.defineProperties(Entity.prototype, properties);
+      Entity.prototype.toJSON = new Function('', `
+        return {
+          ${sorted.map((type) => `${type}: this.${type}`).join(', ')}
+        };
+      `);
+      walk.class = Entity;
+    }
+    return walk.class;
+  }
+}
+

src/ecs/index.js

@@ -0,0 +1,3 @@
+/* v8 ignore start */
+export {default as Ecs} from './ecs.js';
+export {default as System} from './system.js';

src/ecs/query.js

@@ -0,0 +1,118 @@
+import BaseComponent from './component/base.js';
+
+export default class Query {
+
+  $$compiled = {with: [], without: []};
+
+  $$index = new Set();
+
+  constructor(parameters, ComponentsAndOrBundles) {
+    for (let i = 0; i < parameters.length; ++i) {
+      const parameter = parameters[i];
+      switch (parameter.charCodeAt(0)) {
+        case '!'.charCodeAt(0):
+          this.$$compiled.without.push(ComponentsAndOrBundles[parameter.slice(1)]);
+          break;
+        default:
+          this.$$compiled.with.push(ComponentsAndOrBundles[parameter]);
+          break;
+      }
+    }
+  }
+
+  get count() {
+    return this.$$index.size;
+  }
+
+  deindex(entities) {
+    for (let i = 0; i < entities.length; ++i) {
+      this.$$index.delete(entities[i]);
+    }
+  }
+
+  reindex(entities) {
+    if (0 === this.$$compiled.with.length && 0 === this.$$compiled.without.length) {
+      for (const entity of entities) {
+        this.$$index.add(entity);
+      }
+      return;
+    }
+    for (const entity of entities) {
+      let should = true;
+      withCheck: for (let j = 0; j < this.$$compiled.with.length; ++j) {
+        const ComponentOrBundle = this.$$compiled.with[j];
+        if (ComponentOrBundle instanceof BaseComponent) {
+          if ('undefined' === typeof ComponentOrBundle.get(entity)) {
+            should = false;
+            break;
+          }
+        }
+        else {
+          for (const k in ComponentOrBundle.Components) {
+            if ('undefined' === typeof ComponentOrBundle.Components[k].get(entity)) {
+              should = false;
+              break withCheck;
+            }
+          }
+        }
+      }
+      if (should) {
+        for (let j = 0; j < this.$$compiled.without.length; ++j) {
+          const ComponentOrBundle = this.$$compiled.without[j];
+          if (ComponentOrBundle instanceof BaseComponent) {
+            if ('undefined' !== typeof ComponentOrBundle.get(entity)) {
+              should = false;
+              break;
+            }
+          }
+          else {
+            let shouldLocal = false;
+            for (const k in ComponentOrBundle.Components) {
+              if ('undefined' === typeof ComponentOrBundle.Components[k].get(entity)) {
+                shouldLocal = true;
+                break;
+              }
+            }
+            if (!shouldLocal) {
+              should = false;
+              break;
+            }
+          }
+        }
+      }
+      if (should) {
+        this.$$index.add(entity);
+      }
+      else if (!should) {
+        this.$$index.delete(entity);
+      }
+    }
+  }
+
+  select() {
+    const it = this.$$index.values();
+    const value = [];
+    return {
+      [Symbol.iterator]() {
+        return this;
+      },
+      next: () => {
+        const result = it.next();
+        if (result.done) {
+          return {done: true, value: undefined};
+        }
+        for (let i = 0; i < this.$$compiled.with.length; ++i) {
+          if (this.$$compiled.with[i] instanceof BaseComponent) {
+            value[i] = this.$$compiled.with[i].get(result.value);
+          }
+          else {
+            value[i] = this.$$compiled.with[i].select(result.value);
+          }
+        }
+        value[this.$$compiled.with.length] = result.value;
+        return {done: false, value};
+      },
+    };
+  }
+
+}

src/ecs/query.test.js

@@ -0,0 +1,116 @@
+import {expect, test} from 'vitest';
+
+import Bundle from './bundle.js';
+import {createComponent} from './component.js';
+import Query from './query.js';
+
+const A = createComponent({a: {type: 'int32', defaultValue: 420}});
+const B = createComponent({b: {type: 'int32', defaultValue: 69}});
+const C = createComponent({c: 'int32'});
+const D = Bundle.normalize(['B', 'C']);
+class E extends Bundle {
+
+  static Components = ['A', 'B'];
+
+  static select(entity, Components) {
+    const {A: {a}, B: {b}} = super.select(entity, Components);
+    return {a, b};
+  }
+
+}
+
+const ComponentsAndOrBundles = {
+  A: new A(),
+  B: new B(),
+  C: new C(),
+};
+ComponentsAndOrBundles.A.createMany([[2], [3]]);
+ComponentsAndOrBundles.B.createMany([[1], [2]]);
+ComponentsAndOrBundles.C.createMany([[2], [4]]);
+ComponentsAndOrBundles.D = new D([ComponentsAndOrBundles.B, ComponentsAndOrBundles.C]);
+ComponentsAndOrBundles.E = new E([ComponentsAndOrBundles.A, ComponentsAndOrBundles.B]);
+
+function testQuery(parameters, expected) {
+  const query = new Query(parameters, ComponentsAndOrBundles);
+  query.reindex([1, 2, 3]);
+  expect(query.count)
+    .to.equal(expected.length);
+  for (const _ of query.select()) {
+    expect(_.length)
+      .to.equal(parameters.filter((spec) => '!'.charCodeAt(0) !== spec.charCodeAt(0)).length + 1);
+    expect(expected.includes(_.pop()))
+      .to.equal(true);
+  }
+}
+
+test('can query all', () => {
+  testQuery([], [1, 2, 3]);
+});
+
+test('can query some', () => {
+  testQuery(['A'], [2, 3]);
+  testQuery(['A', 'B'], [2]);
+});
+
+test('can query excluding', () => {
+  testQuery(['!A'], [1]);
+  testQuery(['A', '!B'], [3]);
+});
+
+test('can query bundles', () => {
+  testQuery(['D'], [2]);
+});
+
+test('can query excluding bundles', () => {
+  testQuery(['!D'], [1, 3]);
+});
+
+test('can deindex', () => {
+  const query = new Query(['A'], ComponentsAndOrBundles);
+  query.reindex([1, 2, 3]);
+  expect(query.count)
+    .to.equal(2);
+  query.deindex([2]);
+  expect(query.count)
+    .to.equal(1);
+});
+
+test('can reindex', () => {
+  const Test = new (createComponent({a: {type: 'int32', defaultValue: 420}}))();
+  Test.createMany([[2], [3]]);
+  const query = new Query(['Test'], {Test});
+  query.reindex([2, 3]);
+  expect(query.count)
+    .to.equal(2);
+  Test.destroy(2);
+  query.reindex([2, 3]);
+  expect(query.count)
+    .to.equal(1);
+});
+
+test('can select', () => {
+  const query = new Query(['A'], ComponentsAndOrBundles);
+  query.reindex([1, 2, 3]);
+  const it = query.select();
+  const result = it.next();
+  expect(result.value[0].a)
+    .to.equal(420);
+});
+
+test('can select bundles', () => {
+  const query = new Query(['D'], ComponentsAndOrBundles);
+  query.reindex([1, 2, 3]);
+  const it = query.select();
+  const result = it.next();
+  expect(result.value[0].B.b)
+    .to.equal(69);
+});
+
+test('can select configured bundles', () => {
+  const query = new Query(['E'], ComponentsAndOrBundles);
+  query.reindex([1, 2, 3]);
+  const it = query.select();
+  const result = it.next();
+  expect(result.value[0])
+    .to.deep.equal({a: 420, b: 69});
+});

src/ecs/schema.js

@@ -0,0 +1,153 @@
+
+export default class Schema {
+
+  defaultValues = {};
+
+  $$size = 0;
+
+  specification;
+
+  constructor(specification) {
+    this.specification = this.constructor.normalize(specification);
+    // Try to calculate static size.
+    for (const i in this.specification) {
+      const {type} = this.specification[i];
+      const size = this.constructor.sizeOfType(type);
+      if (0 === size) {
+        this.$$size = 0;
+        break;
+      }
+      this.$$size += size;
+    }
+    for (const i in this.specification) {
+      const {type} = this.specification[i];
+      this.defaultValues[i] = this.specification[i].defaultValue;
+      if ('undefined' === typeof this.defaultValues[i] && 'string' === type) {
+        this.defaultValues[i] = '';
+      }
+    }
+  }
+
+  [Symbol.iterator]() {
+    const keys = Object.keys(this.specification);
+    return {
+      next: () => {
+        if (0 === keys.length) {
+          return {done: true};
+        }
+        const key = keys.shift();
+        return {
+          done: false,
+          value: [key, this.specification[key]],
+        };
+      },
+    };
+  }
+
+  has(key) {
+    return key in this.specification;
+  }
+
+  static normalize(specification) {
+    const normalized = Object.create(null);
+    for (const i in specification) {
+      normalized[i] = 'string' === typeof specification[i]
+        ? {type: specification[i]}
+        : specification[i];
+      if (!this.validateType(normalized[i].type)) {
+        throw new TypeError(`unknown schema type: ${normalized[i].type}`);
+      }
+    }
+    return normalized;
+  }
+
+  readSize(view, cursor) {
+    let fullSize = 0;
+    for (const i in this.specification) {
+      const {type} = this.specification[i];
+      const size = this.constructor.sizeOfType(type);
+      if (0 === size) {
+        switch (type) {
+          case 'string': {
+            const length = view.getUint32(cursor, true);
+            cursor += 4 + length;
+            fullSize += 4;
+            fullSize += length;
+            break;
+          }
+        }
+      }
+      else {
+        cursor += size;
+        fullSize += size;
+      }
+    }
+    return fullSize;
+  }
+
+  get size() {
+    return this.$$size;
+  }
+
+  sizeOf(instance) {
+    let fullSize = 0;
+    for (const i in this.specification) {
+      const {type} = this.specification[i];
+      const size = this.constructor.sizeOfType(type);
+      if (0 === size) {
+        switch (type) {
+          case 'string':
+            fullSize += 4;
+            fullSize += instance[i].length;
+            break;
+        }
+      }
+      else {
+        fullSize += size;
+      }
+    }
+    return fullSize;
+  }
+
+  static sizeOfType(type) {
+    switch (type) {
+      case 'uint8': case 'int8': return 1;
+      case 'uint16': case 'int16': return 2;
+      case 'uint32': case 'int32': case 'float32': return 4;
+      case 'float64': case 'int64': case 'uint64': return 8;
+      default: return 0;
+    }
+  }
+
+  static validateType(type) {
+    return [
+      'float32', 'float64',
+      'int8', 'int16', 'int32', 'int64',
+      'string',
+      'uint8', 'uint16', 'uint32', 'uint64',
+    ]
+      .includes(type);
+  }
+
+  static viewMethodFromType(type) {
+    const capitalizedType = `${type.slice(0, 1).toUpperCase()}${type.slice(1)}`;
+    switch (type) {
+      case 'uint8':
+      case 'int8':
+      case 'uint16':
+      case 'int16':
+      case 'uint32':
+      case 'int32':
+      case 'float32':
+      case 'float64': {
+        return capitalizedType;
+      }
+      case 'int64':
+      case 'uint64': {
+        return `Big${capitalizedType}`;
+      }
+      default: return undefined;
+    }
+  }
+
+}

src/ecs/schema.test.js

@@ -0,0 +1,22 @@
+import {expect, test} from 'vitest';
+
+import Schema from './schema.js';
+
+test('validates a schema', () => {
+  expect(() => {
+    new Schema({test: 'unknown'})
+  })
+    .to.throw();
+  expect(() => {
+    new Schema({test: 'unknown'})
+  })
+    .to.throw();
+
+});
+
+test('calculates the size of an instance', () => {
+  expect((new Schema({foo: 'uint8', bar: 'uint32'})).sizeOf({foo: 69, bar: 420}))
+    .to.equal(5);
+  expect((new Schema({foo: 'string'})).sizeOf({foo: 'hi'}))
+    .to.equal(4 + 2);
+});

src/ecs/serializer.js

@@ -0,0 +1,61 @@
+import Schema from './schema.js';
+
+export default class Serializer {
+
+  constructor(schema) {
+    this.schema = schema instanceof Schema ? schema : new Schema(schema);
+  }
+
+  decode(view, destination, offset = 0) {
+    let cursor = offset;
+    for (const [key, {type}] of this.schema) {
+      const viewMethod = Schema.viewMethodFromType(type);
+      let value;
+      if (viewMethod) {
+        value = view[`get${viewMethod}`](cursor, true);
+        cursor += Schema.sizeOfType(type);
+      }
+      else {
+        switch (type) {
+          case 'string': {
+            const length = view.getUint32(cursor, true);
+            cursor += 4;
+            const {buffer, byteOffset} = view;
+            const decoder = new TextDecoder();
+            value = decoder.decode(new DataView(buffer, byteOffset + cursor, length));
+            cursor += length;
+            break;
+          }
+        }
+      }
+      destination[key] = value;
+    }
+  }
+
+  encode(source, view, offset = 0) {
+    let cursor = offset;
+    for (const [key, {type}] of this.schema) {
+      const viewMethod = Schema.viewMethodFromType(type);
+      if (viewMethod) {
+        view[`set${viewMethod}`](cursor, source[key], true);
+        cursor += Schema.sizeOfType(type);
+      }
+      else {
+        switch (type) {
+          case 'string': {
+            const lengthOffset = cursor;
+            cursor += 4;
+            const encoder = new TextEncoder();
+            const bytes = encoder.encode(source[key]);
+            for (let i = 0; i < bytes.length; ++i) {
+              view.setUint8(cursor++, bytes[i]);
+            }
+            view.setUint32(lengthOffset, bytes.length, true);
+            break;
+          }
+        }
+      }
+    }
+  }
+
+}

src/ecs/serializer.test.js

@@ -0,0 +1,32 @@
+import {expect, test} from 'vitest';
+
+import Serializer from './serializer.js';
+
+test('can encode and decode', () => {
+  const entries = [
+    ['uint8', 255],
+    ['int8', -128],
+    ['int8', 127],
+    ['uint16', 65535],
+    ['int16', -32768],
+    ['int16', 32767],
+    ['uint32', 4294967295],
+    ['int32', -2147483648],
+    ['int32', 2147483647],
+    ['uint64', 18446744073709551615n],
+    ['int64', -9223372036854775808n],
+    ['int64', 9223372036854775807n],
+    ['float32', 0.5],
+    ['float64', 1.234],
+    ['string', 'hello world'],
+  ];
+  const schema = entries.reduce((r, [type]) => ({...r, [Object.keys(r).length]: type}), {});
+  const data = entries.reduce((r, [, value]) => ({...r, [Object.keys(r).length]: value}), {});
+  const serializer = new Serializer(schema);
+  const view = new DataView(new ArrayBuffer(serializer.schema.sizeOf(data)));
+  serializer.encode(data, view);
+  const result = {};
+  serializer.decode(view, result);
+  expect(data)
+    .to.deep.equal(result);
+});

src/ecs/system.js

@@ -0,0 +1,69 @@
+
+import Query from './query.js';
+
+export default class System {
+
+  destroying = [];
+
+  queries = {};
+
+  constructor(Components) {
+    const queries = this.constructor.queries();
+    for (const i in queries) {
+      this.queries[i] = new Query(queries[i], Components);
+    }
+  }
+
+  deindex(entities) {
+    for (const i in this.queries) {
+      this.queries[i].deindex(entities);
+    }
+  }
+
+  destroyEntity(entity) {
+    this.destroyManyEntities([entity]);
+  }
+
+  destroyManyEntities(entities) {
+    for (let i = 0; i < entities.length; i++) {
+      this.destroying.push(entities[i]);
+    }
+  }
+
+  finalize() {}
+
+  static normalize(SystemLike) {
+    if (SystemLike.prototype instanceof System) {
+      return SystemLike;
+    }
+    if ('function' === typeof SystemLike) {
+      class TickingSystem extends System {}
+      TickingSystem.prototype.tick = SystemLike;
+      return TickingSystem;
+    }
+    /* v8 ignore next */
+    throw new TypeError(`Couldn't normalize '${SystemLike}' as a system`);
+  }
+
+  static queries() {
+    return {};
+  }
+
+  reindex(entities) {
+    for (const i in this.queries) {
+      this.queries[i].reindex(entities);
+    }
+  }
+
+  select(query) {
+    return this.queries[query].select();
+  }
+
+  tickDestruction() {
+    this.deindex(this.destroying);
+    this.destroying = [];
+  }
+
+  tick() {}
+
+}

src/index.js

@@ -3,6 +3,8 @@ import {createRoot} from 'react-dom/client';
 
 import Silphius from './components/silphius.jsx';
 
+await import('./isomorphinit.js');
+
 // Setup DOM.
 createRoot(document.querySelector('.silphius'))
   .render(createElement(Silphius));

src/isomorphinit.js

@@ -0,0 +1,14 @@
+// Gathering.
+const {default: PacketClass} = await import('./net/packet/packet.js');
+Object.values(await import('./net/packet/packets.js'))
+  .forEach((Packet) => {
+    PacketClass.register(Packet);
+  });
+PacketClass.mapRegistered();
+
+const {default: Ecs} = await import('./ecs/ecs.js');
+Ecs.ComponentLikesAndOrBundleLikes = Object.fromEntries(
+  Object.entries(
+    await import('./ecs/components.js'),
+  ),
+);

src/net/client/client.js

@@ -1,10 +1,13 @@
+import Packet from '../packet/packet.js';
+
 export default class Client {
   constructor() {
     this.listeners = [];
   }
-  accept(data) {
+  accept(packed) {
+    const decoded = Packet.accept(packed);
     for (const i in this.listeners) {
-      this.listeners[i](data);
+      this.listeners[i](decoded);
     }
   }
   addMessageListener(listener) {
@@ -16,4 +19,7 @@ export default class Client {
       this.listeners.splice(index, 1);
     }
   }
+  send(packet) {
+    this.transmit(Packet.transmit(packet));
+  }
 }

src/net/client/local.js

@@ -2,12 +2,12 @@ import Client from './client.js';
 
 export default class LocalClient extends Client {
   async connect() {
-    this.worker = new Worker('../server/worker.js', {type: 'module'});
+    this.worker = new Worker('/net/server/worker.js', {type: 'module'});
     this.worker.onmessage = (event) => {
       this.accept(event.data);
     };
   }
-  send(message) {
+  transmit(packed) {
-    this.worker.postMessage(message);
+    this.worker.postMessage(packed);
   }
 }

src/net/client/remote.js

@@ -3,15 +3,15 @@ import Client from './client.js';
 export default class RemoteClient extends Client {
   async connect() {
     this.socket = new WebSocket(`ws://${window.location.host}/ws`);
+    this.socket.binaryType = 'arraybuffer';
     this.socket.onmessage = (event) => {
-      this.accept(JSON.parse(event.data));
+      this.accept(event.data);
     };
     await new Promise((resolve) => {
       this.socket.onopen = resolve;
     });
   }
-  send(message) {
+  transmit(packed) {
-    this.socket.send(JSON.stringify(message));
+    this.socket.send(packed);
   }
 }
-

src/net/packet/action.js

@@ -0,0 +1,33 @@
+import Packet from './packet.js';
+
+const WIRE_MAP = {
+  'moveUp': 0,
+  'moveRight': 1,
+  'moveDown': 2,
+  'moveLeft': 3,
+};
+Object.entries(WIRE_MAP)
+  .forEach(([k, v]) => {
+    WIRE_MAP[v] = k;
+  });
+
+export default class Action extends Packet {
+
+  static type = 'action';
+
+  static pack(payload) {
+    return super.pack({
+      type: WIRE_MAP[payload.type],
+      value: payload.value,
+    });
+  }
+
+  static unpack(packed) {
+    const unpacked = super.unpack(packed);
+    return {
+      type: WIRE_MAP[unpacked.type],
+      value: unpacked.value,
+    };
+  }
+
+};

src/net/packet/connect.js

@@ -0,0 +1,7 @@
+import Packet from './packet.js';
+
+export default class Connect extends Packet {
+
+  static type = 'connect';
+
+};

src/net/packet/connected.js

@@ -0,0 +1,7 @@
+import Packet from './packet.js';
+
+export default class Connected extends Packet {
+
+  static type = 'connected';
+
+};

src/net/packet/packet.js

@@ -0,0 +1,68 @@
+import {encode, decode} from '@msgpack/msgpack';
+
+export default class Packet {
+
+  static registered = {};
+
+  constructor(payload = {}) {
+    this.payload = payload;
+  }
+
+  static accept(packed) {
+    const decoded = decode(packed);
+    const Packet = this.registered[decoded.id];
+    return {
+      type: Packet.type,
+      payload: Packet.unpack(decoded),
+    };
+  }
+
+  static decode(buffer) {
+    try {
+      return this.unpack(decode(buffer));
+    }
+    catch (error) {
+      throw new Error(`decoding ${this.type}: ${error.message}`);
+    }
+  }
+
+  static encode(payload) {
+    try {
+      return encode(this.pack(payload));
+    }
+    catch (error) {
+      throw new Error(`encoding ${this.type}: ${error.message}`);
+    }
+  }
+
+  static mapRegistered() {
+    this.registered = Object.fromEntries([
+      ...Object.entries(this.registered),
+      ...Object.entries(this.registered)
+        .map(([, Packet], id) => {
+          Packet.id = id;
+          return [id, Packet];
+        }),
+    ]);
+  }
+
+  static pack(payload) {
+    return {
+      id: this.id,
+      payload,
+    };
+  }
+
+  static register(Packet) {
+    this.registered[Packet.type] = Packet;
+  }
+
+  static transmit({type, payload}) {
+    return this.registered[type].encode(payload);
+  }
+
+  static unpack({payload}) {
+    return payload;
+  }
+
+}

src/net/packet/packets.js

@@ -0,0 +1,4 @@
+export {default as Action} from './action.js';
+export {default as Connect} from './connect.js';
+export {default as Connected} from './connected.js';
+export {default as Tick} from './tick.js';

src/net/packet/tick.js

@@ -0,0 +1,7 @@
+import Packet from './packet.js';
+
+export default class Tick extends Packet {
+
+  static type = 'tick';
+
+};

src/net/server/server.js

@@ -0,0 +1,117 @@
+import {MOVE_MAP} from '../../constants.js';
+import Cell from '../../cell.js';
+import {System} from '../../ecs/index.js';
+import Packet from "../packet/packet.js";
+
+const SPEED = 100;
+const TPS = 60;
+
+await import ('../../isomorphinit.js');
+
+class MovementSystem extends System {
+
+  static queries() {
+    return {
+      default: ['Position', 'Controlled'],
+    };
+  }
+
+  tick(elapsed) {
+    for (const [position, controlled] of this.select('default')) {
+      position.x += SPEED * elapsed * (controlled.right - controlled.left);
+      position.y += SPEED * elapsed * (controlled.down - controlled.up);
+    }
+  }
+
+}
+
+export default class Server {
+
+  constructor() {
+    this.cells = [new Cell()];
+    this.cells[0].ecs.addSystem(MovementSystem);
+    this.connections = [];
+    this.connectedPlayers = new Map();
+    this.frame = 0;
+    this.last = Date.now();
+  }
+
+  accept(connection, packed) {
+    const decoded = Packet.accept(packed);
+    const {payload, type} = decoded;
+    switch (type) {
+      case 'connect': {
+        this.send(
+          connection,
+          {
+            type: 'connected',
+            payload: [],
+          },
+        );
+        break;
+      }
+      case 'action': {
+        const {ecs} = this.cells[0];
+        const connectedPlayer = this.connectedPlayers.get(connection);
+        if (payload.type in MOVE_MAP) {
+          ecs.get(connectedPlayer).Controlled[MOVE_MAP[payload.type]] = payload.value;
+        }
+        break;
+      }
+      default:
+    }
+  }
+
+  connectPlayer(connection) {
+    this.connections.push(connection);
+    const {ecs} = this.cells[0];
+    const entity = ecs.create({
+      Controlled: {up: 0, right: 0, down: 0, left: 0},
+      Position: {x: 50, y: 50},
+      Visible: {image: './assets/bunny.png'},
+    })
+    this.connectedPlayers.set(connection, entity);
+  }
+
+  disconnectPlayer(connection) {
+    this.connectedPlayers.delete(connection);
+    this.connections.splice(this.connections.indexOf(connection), 1);
+  }
+
+  async load() {
+  }
+
+  send(connection, packet) {
+    this.transmit(connection, Packet.transmit(packet));
+  }
+
+  start() {
+    return setInterval(() => {
+      const elapsed = (Date.now() - this.last) / 1000;
+      this.last = Date.now();
+      this.tick(elapsed);
+    }, 1000 / TPS);
+  }
+
+  tick(elapsed) {
+    this.cells[0].ecs.tick(elapsed);
+    const {ecs} = this.cells[0];
+    const view = new DataView(new ArrayBuffer(ecs.sizeOf(ecs.entities)));
+    ecs.encode(ecs.entities, view);
+    for (const connection of this.connections) {
+      this.send(
+        connection,
+        {
+          type: 'tick',
+          payload: {
+            entities: view,
+            elapsed,
+            frame: this.frame,
+          },
+        },
+      );
+    }
+    this.frame += 1;
+  }
+
+}

src/net/server/socket.js

@@ -9,14 +9,18 @@ const {
 const wss = new WebSocketServer({port: SILPHIUS_WEBSOCKET_PORT});
 
 const server = new class SocketServer extends Server {
-  send(ws, data) { ws.send(JSON.stringify(data)); }
+  transmit(ws, packed) { ws.send(packed); }
 }
 
+await server.load();
 server.start();
 
 wss.on('connection', function connection(ws) {
   server.connectPlayer(ws);
-  ws.on('message', function message(data) {
+  ws.on('close', () => {
-    server.accept(ws, JSON.parse(data));
+    server.disconnectPlayer(ws);
+  })
+  ws.on('message', (packed) => {
+    server.accept(ws, packed);
   });
 });

src/net/server/worker.js

@@ -1,11 +1,12 @@
 import Server from './server.js';
 
 const server = new class WorkerServer extends Server {
-  send(connection, data) { postMessage(data); }
+  transmit(connection, packed) { postMessage(packed); }
 }
 
+await server.load();
 server.start();
 
 server.connectPlayer(undefined);
 
-onmessage = ({data}) => { server.accept(undefined, data); };
+onmessage = (event) => { server.accept(undefined, event.data); };

src/server/server.js

@@ -1,79 +0,0 @@
-const SPEED = 100;
-const TPS = 20;
-
-const MOVE_MAP = {
-  'moveUp': 0,
-  'moveRight': 1,
-  'moveDown': 2,
-  'moveLeft': 3,
-};
-
-export default class Server {
-
-  constructor() {
-    this.connections = [];
-    this.connectedPlayers = new Map();
-    this.entities = [];
-    this.frame = 0;
-    this.last = Date.now();
-  }
-
-  accept(connection, {type, payload}) {
-    switch (type) {
-      case 'connect': {
-        this.send(connection, {type: 'connected', payload: Array.from(this.connectedPlayers.values())});
-        break;
-      }
-      case 'action': {
-        const connectedPlayer = this.connectedPlayers.get(connection);
-        if (payload.type in MOVE_MAP) {
-          connectedPlayer.movement[MOVE_MAP[payload.type]] = payload.value;
-        }
-        break;
-      }
-      default:
-    }
-  }
-
-  connectPlayer(connection) {
-    this.connections.push(connection);
-    const entity = {
-      image: './assets/bunny.png',
-      movement: [0, 0, 0, 0],
-      position: [50, 50],
-    };
-    this.entities.push(entity);
-    this.connectedPlayers.set(connection, entity);
-  }
-
-  start() {
-    return setInterval(() => {
-      const elapsed = (Date.now() - this.last) / 1000;
-      this.last = Date.now();
-      this.tick(elapsed);
-    }, 1000 / TPS);
-  }
-
-  tick(elapsed) {
-    for (const connection of this.connections) {
-      const {movement, position} = this.connectedPlayers.get(connection);
-      position[0] += SPEED * elapsed * (movement[1] - movement[3]);
-      position[1] += SPEED * elapsed * (movement[2] - movement[0]);
-    }
-    for (const connection of this.connections) {
-      this.send(
-        connection,
-        {
-          type: 'tick',
-          payload: {
-            entities: this.entities,
-            elapsed,
-            frame: this.frame,
-          },
-        },
-      );
-    }
-    this.frame += 1;
-  }
-
-}

src/stories/dom-decorator.jsx

@@ -1,7 +1,7 @@
 import {useEffect, useRef, useState} from 'react';
 
-import Dom from '../components/dom';
+import Dom from '../components/dom.jsx';
-import {RESOLUTION} from '../constants';
+import {RESOLUTION} from '../constants.js';
 
 function Decorator({children, style}) {
   const ref = useRef();

src/stories/hotbar.stories.js

@@ -1,11 +1,9 @@
 import {useArgs} from '@storybook/preview-api';
 import {fn} from '@storybook/test';
-import {createElement} from 'react';
 
 import potion from '../assets/potion.png';
-import Hotbar from '../components/hotbar';
+import Hotbar from '../components/hotbar.jsx';
-import Dom from '../components/dom';
+import DomDecorator from './dom-decorator.jsx';
-import DomDecorator from './dom-decorator';
 
 const slots = Array(10).fill({});
 slots[2] = {image: potion, qty: 24};

src/stories/slot.stories.js

@@ -1,8 +1,6 @@
-import {createElement} from 'react';
-
 import potion from '../assets/potion.png';
-import Slot from '../components/slot';
+import Slot from '../components/slot.jsx';
-import DomDecorator from './dom-decorator';
+import DomDecorator from './dom-decorator.jsx';
 
 export default {
   title: 'Dom/Inventory/Slot',