Mongodb Mongoose 聚合和多级组

我有MongoDB数据库，有很多不同的硬币，需要在多级输出中聚合它们，但不确定如何进行.我正在使用Mongoose在后端，需要创建与express 路由，将获得硬币，并以我需要的方式排序，以便我在应用程序内的前端更容易.我在这里找到了很多多级群的例子，但没有一个与我的情况不符，我可以让它发挥作用.

-你是什么意思？

[
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "AND",
    "denomination": 0.01,
    "series": 1
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "AND",
    "denomination": 0.01,
    "series": 1
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "BEL",
    "denomination": 0.01,
    "series": 1
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "BEL",
    "denomination": 0.02,
    "series": 1
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "BEL",
    "denomination": 0.5,
    "series": 2
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "ESP",
    "denomination": 0.2,
    "series": 1
  },
  {
    "_id": "643d5bf4637daa055466d8f0",
    "country": "ESP",
    "denomination": 0.05,
    "series": 3
  }
]

我需要这样的输出

-你在做什么？

[
  {
    "country": "AND",
    "series": [
      {
        "series": 1,
        "coins": [
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "AND",
            "denomination": 0.01,
            "series": 1
          },
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "AND",
            "denomination": 0.01,
            "series": 1
          }
        ]
      }
    ]
  },
  {
    "country": "BEL",
    "series": [
      {
        "series": 1,
        "coins": [
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "BEL",
            "denomination": 0.01,
            "series": 1
          },
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "BEL",
            "denomination": 0.02,
            "series": 1
          }
        ]
      },
      {
        "series": 2,
        "coins": [
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "BEL",
            "denomination": 0.5,
            "series": 2
          }
        ]
      }
    ]
  },
  {
    "country": "ESP",
    "series": [
      {
        "series": 1,
        "coins": [
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "ESP",
            "denomination": 0.2,
            "series": 1
          }
        ]
      },
      {
        "series": 3,
        "coins": [
          {
            "_id": "643d5bf4637daa055466d8f0",
            "country": "ESP",
            "denomination": 0.05,
            "series": 2
          }
        ]
      }
    ]
  }
]

到目前为止，我已经完成了这项工作，但不知道如何从这一点开始按正确的顺序推硬币.

const coins = await Coin.aggregate([
    {
      $group: {
        _id: '$country',
        series: { $addToSet: { series: '$series', coins: [] } },
      },
    },
    {
      $addFields: { country: '$_id' },
    },
    {
      $project: {
        _id: 0,
      },
    },
    {
      $sort: { country: 1 },
    },
 ]);