import { onAppTrimMemory, offAppTrimMemory ,onAppActivityDestroy} from "io.dcloud.uts.android"

let listeners: UTSCallback[] = []

const onAppTrimMemoryListener = (res: number) => {
    listeners.forEach(listener => {
        listener(res)
    })
}

export function onMemoryWarning(callback: (res: number) => void) {
    if (listeners.length === 0) {
		// 仅首次执行底层的实际监听
        onAppTrimMemory(onAppTrimMemoryListener)
		onAppActivityDestroy(()=>{
			// listeners 默认是静态常量周期，activity 销毁时，需要手动清空
			listeners = []
		})
    }
    listeners.push(callback)
}

export function offMemoryWarning(callback: UTSCallback | null = null) {
	
	if(callback == null){
		// 清除全部回调
		listeners = []
		offAppTrimMemory(null);
		return
	}
	
	// 清除指定回调
    const index = listeners.indexOf(callback)
    if (index > -1) {
        listeners.splice(index, 1)
    }
    if (listeners.length === 0) {
        // 当用户不再监听时，移除底层实际监听
        offAppTrimMemory(onAppTrimMemoryListener)
    }
}