start testing Simulation

eslint.config.mjs

@@ -18,7 +18,8 @@ export default tseslint.config(
   },
   {
     rules: {
-      'semi': ['error', 'never']
+      semi: ['error', 'never'],
+      quotes: ['error', 'single']
     }
   }
 )

jest.config.js

@@ -1,8 +1,8 @@
 /** @type {import('ts-jest').JestConfigWithTsJest} **/
 // eslint-disable-next-line no-undef
 module.exports = {
-  testEnvironment: "node",
+  testEnvironment: 'node',
   transform: {
-    "^.+.tsx?$": ["ts-jest", {}],
+    '^.+.tsx?$': ['ts-jest', {}],
   },
 }

rollup.config.mjs

@@ -17,7 +17,6 @@ export default {
       sourcemap: true
     }
   ],
-  external: ['node:events'],
   plugins: [
     typescript()
   ]

src/Body.spec.ts

@@ -1,5 +1,5 @@
-import Body from "./Body"
-import Vector from "./Vector"
+import Body from './Body'
+import Vector from './Vector'
 
 describe('Body', () => {
   describe('setExternalForces', () => {

src/Simulation.spec.ts

@@ -0,0 +1,52 @@
+import Body from './Body'
+import Simulation from './Simulation'
+import Vector from './Vector'
+
+describe('Simulation', () => {
+  it('should call changeCallback', async () => {
+    let resolver: (value?: unknown) => void
+    const promise = new Promise((resolve) => { resolver = resolve })
+
+    const simulation = new Simulation({
+      bodies: [],
+      renderInterval: 0,
+      changeCallback: () => { resolver() }
+    })
+
+    await promise
+    simulation.stop()
+  })
+
+  it('should move bodies through universe', async () => {
+    let resolver: (value?: unknown) => void
+    const promise = new Promise((resolve) => { resolver = resolve })
+
+    const startingPositions = [
+      new Vector(1, 1, 1),
+      new Vector(-1, -1, -1)
+    ]
+
+    const simulation = new Simulation({
+      bodies: [
+        new Body({
+          position: startingPositions[0],
+          velocity: new Vector(0, 0, 0)
+        }),
+        new Body({
+          position: startingPositions[1],
+          velocity: new Vector(0, 0, 0)
+        })
+      ],
+      renderInterval: 0,
+      changeCallback: () => { resolver() }
+    })
+
+    expect(simulation.bodies).toBe(simulation.universe.bodies)
+
+    await promise
+    simulation.stop()
+
+    expect(simulation.bodies[0].position).not.toEqual(startingPositions[0])
+    expect(simulation.bodies[1].position).not.toEqual(startingPositions[1])
+  })
+})

src/Simulation.ts

@@ -1,4 +1,3 @@
-import EventEmitter from 'node:events'
 import Universe from './Universe'
 import Body from './Body'
 
@@ -10,8 +9,8 @@ export default class Simulation {
   renderInterval: number
 
   universe: Universe
-  eventEmitter: EventEmitter
   simulationInterval: NodeJS.Timeout
+  changeCallback: () => void
 
   constructor({
     /** orbital bodies in the simulation */
@@ -23,19 +22,23 @@ export default class Simulation {
     /** simulation time elapsed between iterations */
     deltaTime,
     /** computer time between iterations */
-    renderInterval
+    renderInterval,
+    /** callback fired when simulation state changes */
+    changeCallback
   }: {
     bodies: Body[]
     gravity?: number
     collisions?: boolean
     deltaTime?: number
     renderInterval?: number
+    changeCallback: () => void
   }) {
     this.bodies = bodies
     this.gravity = gravity ?? 6.674e-11
     this.collisions = collisions ?? false
     this.deltaTime = deltaTime ?? 0.5
     this.renderInterval = renderInterval ?? 10
+    this.changeCallback = changeCallback
 
     this.universe = new Universe({
       bodies: this.bodies,
@@ -44,10 +47,20 @@ export default class Simulation {
       deltaTime: this.deltaTime
     })
 
-    this.eventEmitter = new EventEmitter()
+    this.start()
+  }
+
+  /** start simulation */
+  start() {
+    clearInterval(this.simulationInterval)
     this.simulationInterval = setInterval(() => {
       this.universe.moveBodiesThroughTime()
-      this.eventEmitter.emit('deltaTime')
-    }, renderInterval)
+      this.changeCallback()
+    }, this.renderInterval)
+  }
+
+  /** stop simulation */
+  stop() {
+    clearInterval(this.simulationInterval)
   }
 }

src/StableUniverses.ts

@@ -84,19 +84,19 @@ export const FigureEight = new Universe({
       mass: 1,
       position: new Vector(0.97000436, -0.24308753, 0),
       velocity: new Vector(0.466203685, 0.43236573, 0),
-      color: "#3d9900"
+      color: '#3d9900'
     }),
     new Body({
       mass: 1,
       position: new Vector(-0.97000436, 0.24308753, 0),
       velocity: new Vector(0.466203685, 0.43236573, 0),
-      color: "#00314e"
+      color: '#00314e'
     }),
     new Body({
       mass: 1,
       position: new Vector(0, 0, 0),
       velocity: new Vector(-0.93240737, -0.86473146, 0),
-      color: "#008ebd"
+      color: '#008ebd'
     })
   ],
   gravity: 1, collisions: false, deltaTime: 0.005

src/Vector.spec.ts

@@ -1,4 +1,4 @@
-import Vector from "./Vector"
+import Vector from './Vector'
 
 describe('Vector', () => {
   describe('constructor', () => {