refactor(core): CORE-02 type emitter maps and fix nested once dispatch

test/public-behavior.test.js

@@ -1,3 +1,4 @@
+import assert from 'node:assert/strict'
 import process from 'node:process'
 // eslint-disable-next-line test/no-import-node-test -- Run the same public contract against each actual implementation.
 import { test } from 'node:test'
@@ -12,3 +13,37 @@ for (const { name, Artplayer } of targets) {
   for (const [id, verify] of Object.entries(emitterContracts))
     test(`${id}: ${name}`, () => verify(Artplayer.Emitter))
 }
+
+test('EVENT.prototype-event-names: candidate supports names that collide with Object.prototype', () => {
+  for (const name of ['__proto__', 'constructor', 'toString', 'hasOwnProperty']) {
+    assert.throws(() => new targets[0].Artplayer.Emitter().on(name, () => {}), error => error.name === 'TypeError')
+    for (const { Artplayer } of targets.slice(1)) {
+      const emitter = new Artplayer.Emitter()
+      let calls = 0
+      const fn = () => calls++
+      emitter.emit(name).off(name)
+      const prototype = Object.getPrototypeOf(emitter.e)
+      emitter.on(name, fn).once(name, fn)
+      emitter.emit(name).emit(name).off(name, fn).emit(name)
+      assert.equal(calls, 3)
+      assert.equal(Object.prototype.hasOwnProperty.call(emitter.e, name), false)
+      assert.equal(Object.getPrototypeOf(emitter.e), prototype)
+    }
+  }
+})
+
+test('EVENT.once-nested-snapshot: candidate consumes a once registration across nested dispatch snapshots', () => {
+  for (const [index, { Artplayer }] of targets.entries()) {
+    const emitter = new Artplayer.Emitter()
+    let nested = false
+    let calls = 0
+    emitter.on('value', () => {
+      if (!nested) {
+        nested = true
+        emitter.emit('value')
+      }
+    }).once('value', () => calls++)
+    emitter.emit('value')
+    assert.equal(calls, index === 0 ? 2 : 1)
+  }
+})