/**
 * H5 上 uni.navigateBack 偶发既不成功也不进 fail；离开 OA web-view 时做兜底。
 * @param {{ fallbackUrl?: string, onStuck?: () => void }} [opts]
 */
export function navigateBackFromOaHost(opts) {
  const onStuck = opts && opts.onStuck

  const currentRoute = () => {
    try {
      const pages = getCurrentPages()
      const cur = pages && pages[pages.length - 1]
      return String((cur && (cur.route || (cur.$page && cur.$page.fullPath))) || '')
    } catch (_) {
      return ''
    }
  }

  const stillOnWebview = () => {
    const route = currentRoute()
    return (
      route.indexOf('oa/start/webview') !== -1 ||
      route.indexOf('oa/webview/') !== -1
    )
  }

  const resolveFallbackUrl = () => {
    const explicit = String((opts && opts.fallbackUrl) || '').trim()
    if (explicit) return explicit
    try {
      const pages = getCurrentPages()
      if (pages && pages.length >= 2) {
        const prev = pages[pages.length - 2]
        const route = prev && prev.route
        if (route) return '/' + String(route).replace(/^\//, '')
      }
    } catch (_) {
      /* ignore */
    }
    return '/pages/oa/start/index'
  }

  const fallback = () => {
    const fallbackUrl = resolveFallbackUrl()
    if (!fallbackUrl) {
      if (onStuck) onStuck()
      return
    }
    uni.redirectTo({
      url: fallbackUrl,
      fail: () => {
        uni.reLaunch({
          url: fallbackUrl,
          fail: () => {
            if (onStuck) onStuck()
          }
        })
      }
    })
  }

  try {
    const pages = getCurrentPages()
    if (pages && pages.length > 1) {
      uni.navigateBack({
        delta: 1,
        fail: () => fallback()
      })
      // H5：navigateBack 偶发静默失败
      setTimeout(() => {
        if (stillOnWebview()) fallback()
      }, 280)
      return
    }
  } catch (_) {
    /* fall through */
  }
  fallback()
}