// 极简事件总线（避免引入额外依赖）

const listeners = new Map()

export function on(event, handler) {
  if (!event || typeof handler !== 'function') return
  const set = listeners.get(event) || new Set()
  set.add(handler)
  listeners.set(event, set)
}

export function off(event, handler) {
  const set = listeners.get(event)
  if (!set) return
  set.delete(handler)
  if (set.size === 0) listeners.delete(event)
}

export function emit(event, payload) {
  const set = listeners.get(event)
  if (!set || set.size === 0) return
  for (const fn of Array.from(set)) {
    try {
      fn(payload)
    } catch (e) {
      // ignore
    }
  }
}