patch: add shared bus module

packages/shared/src/__tests__/bus.test.ts

@@ -0,0 +1,81 @@
+import { createBus } from 'bus';
+
+describe('bus', () => {
+  it('should be a function', () => {
+    expect(createBus).toBeInstanceOf(Function);
+  });
+
+  it('should return a bus', () => {
+    const bus = createBus();
+    expect(bus).toBeInstanceOf(Object);
+    expect(bus.emit).toBeInstanceOf(Function);
+    expect(bus.on).toBeInstanceOf(Function);
+  });
+
+  it('should emit events', () => {
+    const bus = createBus();
+    const spy = jest.fn();
+    bus.on('test', spy);
+    bus.emit('test');
+    expect(spy).toHaveBeenCalled();
+  });
+
+  it('should emit events with data', () => {
+    const bus = createBus();
+    const spy = jest.fn();
+    bus.on('test', spy);
+    bus.emit('test', 'testData');
+    expect(spy).toHaveBeenCalledWith('testData');
+  });
+
+  it('should emit events with multiple listeners', () => {
+    const bus = createBus();
+    const spy1 = jest.fn();
+    const spy2 = jest.fn();
+    bus.on('test', spy1);
+    bus.on('test', spy2);
+    bus.emit('test');
+    expect(spy1).toHaveBeenCalled();
+    expect(spy2).toHaveBeenCalled();
+  });
+
+  it('should emit events with multiple listeners and data', () => {
+    const bus = createBus();
+    const spy1 = jest.fn();
+    const spy2 = jest.fn();
+    bus.on('test', spy1);
+    bus.on('test', spy2);
+    bus.emit('test', 'test1');
+    expect(spy1).toHaveBeenCalledWith('test1');
+    expect(spy2).toHaveBeenCalledWith('test1');
+  });
+
+  test('on returns an object with an `off` function', () => {
+    const bus = createBus();
+    const spy = jest.fn();
+    const off = bus.on('test', spy);
+    expect(off).toBeInstanceOf(Object);
+    expect(off.off).toBeInstanceOf(Function);
+  });
+
+  test('off should remove a listener', () => {
+    const bus = createBus();
+    const spy = jest.fn();
+    const off = bus.on('test', spy);
+    off.off();
+    bus.emit('test');
+    expect(spy).not.toHaveBeenCalled();
+  });
+
+  test('off should only remove specific handler', () => {
+    const bus = createBus();
+    const spy1 = jest.fn();
+    const spy2 = jest.fn();
+    const off = bus.on('test', spy1);
+    bus.on('test', spy2);
+    off.off();
+    bus.emit('test');
+    expect(spy1).not.toHaveBeenCalled();
+    expect(spy2).toHaveBeenCalled();
+  });
+});

packages/shared/src/bus.ts

@@ -0,0 +1,32 @@
+export function createBus(): {
+  on: (event: string, handler: (...args: any[]) => void) => { off: () => void };
+  emit: (event: string, ...args: any[]) => void;
+} {
+  const listeners: Record<string, ((...args: any[]) => void)[]> = {};
+
+  return {
+    emit(event: string, data: any) {
+      if (!listeners[event]) {
+        return;
+      }
+
+      listeners[event].forEach(listener => {
+        listener(data);
+      });
+    },
+
+    on(event: string, handler: (...args: any[]) => void): { off: () => void } {
+      if (!listeners[event]) {
+        listeners[event] = [];
+      }
+
+      listeners[event].push(handler);
+
+      return {
+        off() {
+          listeners[event] = listeners[event].filter(h => h !== handler);
+        },
+      };
+    },
+  };
+}