import { AppState } from 'react-native'

type Task = () => any | Promise<any>
/**
 * This scheduler runs the supplied task on a scheduled interval.
 * Unlike `setInterval`, it will ensure that a long running task is done before starting a new one.
 * @param task the task to run
 * @param interval the interval
 * @param foregroundOnly if true, the task will only run when the app is in the foreground
 * @returns A function to stop the recurring task
 */
export const scheduleRecurringTask = (
  task: Task,
  interval: number,
  foregroundOnly = false
) => {
  let isRunning = true
  let timeoutId: number | undefined
  let handleAppStateChangeListener: any = null

  const taskWrapper = async () => {
    if (!isRunning) return
    try {
      await task()
    } catch (e) {
      console.error('An error occured in scheduled task:', e)
    } finally {
      if (isRunning) {
        scheduleNextRun()
      }
    }
  }

  const handleAppStateChange = async (appState: string) => {
    if (appState !== 'active') {
      return
    }

    if (
      handleAppStateChangeListener &&
      handleAppStateChangeListener.remove &&
      typeof handleAppStateChangeListener.remove === 'function'
    ) {
      handleAppStateChangeListener.remove()
    } else {
      AppState.removeEventListener('change', handleAppStateChange)
    }

    await taskWrapper()
  }

  const scheduleNextRun = () => {
    timeoutId = window.setTimeout(async () => {
      if (foregroundOnly && AppState.currentState !== 'active') {
        handleAppStateChangeListener = AppState.addEventListener(
          'change',
          handleAppStateChange
        )
        return
      }
      await taskWrapper()
    }, interval)
  }

  scheduleNextRun()

  const stop = () => {
    isRunning = false
    window.clearTimeout(timeoutId)
  }
  return stop
}