Пн goose совокупные заказы для расчета прибыли заказанных товаров

Question

У меня есть две коллекции. Образец коллекции product выглядит следующим образом:

{
  "_id": "5da3e8e90ddb8a7bb9b404d1",
  "updatedAt": "2020-01-07T09:20:02.170Z",
  "createdAt": "2019-10-14T03:18:01.421Z",
  "brief": {
    "category": ",Groceries,Chocolate",
    "images": [ "m & m chocolate peanut 45g.jpg" ],
    "stock": 10,
    "cost": 1.05,
    "price": 1.75,
    "name": "M&M's Chocolate Peanut",
    "code": "SHFP01-019"
  }
}

И образец коллекции Order приводится ниже:

 {
    "_id" : ObjectId("5e26558fc63ab131c518b588"),
    "updatedAt" : ISODate("2020-01-21T08:46:32.734Z"),
    "createdAt" : ISODate("2020-01-21T01:36:15.817Z"),
    "__v" : 0,
    "buyer_id" : ObjectId("5dd214a18c34403071166ebd"),
    "OrderNo" : "ORD-210",
    "products" : [ 
        {
            "variants" : [ 
                {
                    "order_qty" : 1
                }
            ],
            "product" : {
                "_id" : ObjectId("5d8197f30ddb8a7bb9b401d4"),
                "brief" : {
                    "category" : ",Drinks,Beverages",
                    "stock" : 10,
                    "price" : 10.5,
                    "name" : "Yeo's Sugar Cane ",
                    "code" : "YEO113",
                    "images" : [ 
                        "Yeo's Sugar Cane 24x250ml.jpg"
                    ],
                }
            },             
        }, 
        {
            "variants" : [ 
                {
                    "order_qty" : 1
                }
            ],
            "product" : {
                "_id" : ObjectId("5d819a760ddb8a7bb9b401e0"),
                "brief" : {
                    "category" : ",Drinks,Beverages",
                    "stock" : 9,
                    "price" : 10.5,
                    "name" : "Yeo's Chrysanthemum Luo Han Guo Tea",
                    "code" : "YEO118",
                    "images" : [ 
                        "Yeo's Chrysanthemum Luo Han Guo 24x250ml.jpg"
                    ],
                }
            },
        }, 
        {
            "variants" : [ 
                {
                    "order_qty" : 1
                }
            ],
            "product" : {
                "_id" : ObjectId("5d81991d0ddb8a7bb9b401d8"),
                "brief" : {
                    "category" : ",Drinks,Beverages",
                    "stock" : 10,
                    "price" : 10.5,
                    "name" : "Yeo's Snow Pear",
                    "code" : "YEO115",
                    "images" : [ 
                        "Yeo's Snow Pear 24x250ml.jpg"
                    ],
                }
            },
        }
    ],
    "commission_status" : "Approved",
    "status" : "Paid"
}

The задача состоит в том, чтобы выяснить заказы конкретного покупателя и рассчитать общую заработанную прибыль (прибыль рассчитывается по формуле: сумма (product_cost* order_quantity) - сумма (product_price * order_quantity).

Я использовал эту функцию, но получил неправильный результат .

 const buyer = await models.Order.aggregate([
        {
          $match: {buyer_id:req.body.buyer}
        },
        {
          "$lookup": {
            from: "products",
            localField: "products.product._id",
            foreignField: "_id",
            as: "product_cost"
          }
        },
        { $unwind: "$total" },
        { $unwind: { path: "$product_cost", preserveNullAndEmptyArrays: true }},
        { $unwind: "$products" },
        { $unwind: "$products.variants" },
        {
          "$group": {
            _id: "$buyer_id",
            amount: {
              $sum: {
                $cond: [
                  { $eq: ["$product_cost._id", "$products.product._id"] },
                  {
                    $multiply: [
                      "$products.product.brief.price",
                      "$products.variants.order_qty"
                    ]
                  },
                  0
                ]
              }
            },
            totalcost: {
              $sum: {
                $cond: [
                  { $eq: ["$product_cost._id", "$products.product._id"] },
                  {
                    $multiply: [
                      "$product_cost.brief.cost",
                      "$products.variants.order_qty"
                    ]
                  },
                  0
                ]
              }
            }
          }
        },
        {
          "$project": {
            profit: {
              $subtract: ["$amount", "$totalcost"]
            }
          }
        },
        {
          "$match": {
            profit: { $gt: 0 }
          }
        }
      ]);