Applied tax in order API(Node+MongoDB)

Suppose i have below Data:

let result = [
  {
    InvoiceID: ORD001,
    orders: [
      {
        taxType: {
          _id: "64e20a255366cca58c047ce9",
          taxName: "Percentage Tax",
          percentage: 2,
          amount: null,
        },

        Name: "Yogurt",
        category: "Dairy Products",
        quantity: 1,
        price: 100,
        appliedTaxAmount: null,
      },
      {
        taxType: {
          _id: "64e20a255366cca58c047ce9",
          taxName: "Amount Tax",
          percentage: null,
          amount: 2,
        },

        Name: "Campa Cola",
        category: "Cold Drinks",
        quantity: 5,
        price: 50,
        appliedTaxAmount: null,
      },
    ],
  },
  {
    InvoiceID: ORD002,
    orders: [
      {
        taxType: {
          _id: "64e20a255366cca58c047ce9",
          taxName: "Amount Tax",
          percentage: null,
          amount: 3,
        },

        Name: "",
        category: "Snacks",
        quantity: 10,
        price: 10,
        appliedTaxAmount: null,
      },
      {
        taxType: {
          _id: "64e20a255366cca58c047ce9",
          taxName: "Percentage Tax",
          percentage: 10,
          amount: null,
        },

        Name: "Campa Cola",
        category: "Cold Drinks",
        quantity: 2,
        price: 10,
        appliedTaxAmount: null,
      },
    ],
  },
];

To calculate the appliedTaxAmount for each order and add the priceWithTax field to each object, you can use the following JavaScript code:

function calcTax(info) {
  for (const data of result) {
    for (const item of data.orders) {
      if (item.taxType.amount === null) {
        item.appliedTaxAmount =
          (item.price * item.quantity * item.taxType.percentage) / 100;
      } else if (item.taxType.percentage === null) {
        item.appliedTaxAmount = item.quantity * item.taxType.amount;
      }

      item.priceWithTax = item.price * item.quantity + item.appliedTaxAmount;
    }
  }
  return info;
}
const response = calcTax(result);
console.log(JSON.stringify(response, null, 2));

You can also achieve similar calculations using MongoDB's aggregation framework. Below is the code:

db.collectionName.aggregate([
  {
    $unwind: "$orders"
  },
  {
    $addFields: {
      "orders.appliedTaxAmount": {
        $cond: {
          if: { $ne: ["$orders.taxType.percentage", null] },
          then: {
            $multiply: [
              "$orders.price",
              "$orders.taxType.percentage",
              "$orders.quantity",
              0.01
            ]
          },
          else: {
            $multiply: ["$orders.taxType.amount", "$orders.quantity"]
          }
        }
      },
      "orders.priceWithTax ": {
        $add: [
          { $multiply: ["$orders.price", "$orders.quantity"] },
          "$orders.appliedTaxAmount"
        ]
      }
    }
  },
  {
    $group: {
      _id: "$InvoiceID",
      InvoiceID: { $first: "$InvoiceID" },
      orders: { $push: "$orders" }
    }
  },
  {
    $group: {
      _id: null,
      result: { $push: "$$ROOT" }
    }
  },
  {
    $project: {
      _id: 0,
      result: 1
    }
  }
])

The response will be in the form of a JSON document containing an array named result:

{
  "result": [
    {
      "InvoiceID": ORD001,
      "orders": [
        {
          "taxType": {
            "_id": "64e20a255366cca58c047ce9",
            "taxName": "TaxOne",
            "percentage": 2,
            "amount": null
          },
          "Name": "Yogurt",
          "category": "Dairy Products",
          "quantity": 1,
          "price": 100,
          "appliedTaxAmount": 2,
          "priceWithTax": 102
        },
        {
          "taxType": {
            "_id": "64e20a255366cca58c047ce9",
            "taxName": "TaxTwo",
            "percentage": null,
            "amount": 2
          },
          "Name": "Campa Cola",
          "category": "Cold Drinks",
          "quantity": 5,
          "price": 50,
          "appliedTaxAmount": 10,
          "priceWithTax": 60
        }
      ]
    },
    {
      "InvoiceID": ORD002,
      "orders": [
        {
          "taxType": {
            "_id": "64e20a255366cca58c047ce9",
            "taxName": "Amount Tax",
            "percentage": null,
            "amount": 3
          },
          "Name": "",
          "category": "Snacks",
          "quantity": 10,
          "price": 10,
          "appliedTaxAmount": 30,
          "priceWithTax": 130
        },
        {
          "taxType": {
            "_id": "64e20a255366cca58c047ce9",
            "taxName": "TaxThree",
            "percentage": 10,
            "amount": null
          },
          "Name": "Campa Cola",
          "category": "Cold Drinks",
          "quantity": 2,
          "price": 10,
          "appliedTaxAmount": 2,
          "priceWithTax": 22
        }
      ]
    }
  ]
}

Above aggregation pipeline performs the following steps:

1. $unwind: Unwinds the orders array to create separate documents for each order line.
2. $addFields: Adds the calculated fields appliedTaxAmountand priceWithTax to each order line.
3. $group: Groups the data by InvoiceID, preserving the orders within each order.
4. Another $group: Groups all the orders into a single result array.
5. $project: Projects only the result field, removing the _id.

Comments

[Robina]

Excellent

[Hugo Hall]

When integrating applied tax in an order API using Node.js and MongoDB, handling tax calculations dynamically is crucial for compliance. With the introduction of UAE Corporate Tax, businesses must ensure their APIs correctly apply tax rates based on regulations. This includes fetching tax percentages from a database, applying them at checkout, and storing transaction details for audits. Implementing middleware for tax validation and automating updates based on UAE Corporate Tax laws can enhance efficiency. Proper API design ensures seamless tax application and regulatory adherence, reducing financial risks.