initial commit

src/helpers/EventEmitter.ts

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+/**
+ * fully typed node-like event emitter
+ * usage: `EventEmitter<{ event: eventDataType }>`
+ */
+export class EventEmitter<T extends {} = {}> {
+	private listeners: { [E in keyof T]: Set<((data: T[E]) => void)> } = Object.create(null)
+	
+	public on<E extends keyof T>(event: E, listener: ((data: T[E]) => void)) {
+		this.listeners[event] ||= new Set()
+		this.listeners[event].add(listener)
+	}
+
+	public off<E extends keyof T>(event: E, listener: ((data: T[E]) => void)) {
+		this.listeners[event]?.delete(listener)
+		if(this.listeners[event]?.size === 0) {
+			delete this.listeners[event]
+		}
+	}
+
+	public once<E extends keyof T>(event: E, listener: ((data: T[E]) => void)) {
+		const wrapped = (data: T[E]) => {
+			this.off(event, wrapped)
+			listener(data)
+		}
+
+		this.on(event, wrapped)
+	}
+
+	protected emit<E extends keyof T>(event: E, data: T[E]) {
+		if(!this.listeners[event]) return
+		for(const listener of this.listeners[event]) {
+			listener(data)
+		}
+	}
+}

src/helpers/SocketAdapter.ts

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+import { EventEmitter } from '../helpers/EventEmitter'
+
+export interface SocketAdapterConstructor {
+	new(url: string): SocketAdapter
+}
+
+/** cross-platform websocket interface */
+export abstract class SocketAdapter extends EventEmitter<{
+	message: string,
+	open: null,
+	close: null,
+	error: any
+}> {
+	public abstract send(message: string): void
+	public abstract close(): void
+}