I am trying to get a specific data model after I run an aggregate pipeline followed by populate but I am falling just short of it.

The desired result in the end is the following:

```
[
  {
    _accountId: "5beee0966d17bc42501f1234",
    name: "Company Name 1",
    contactEmail: "email1@email.com",
    contactName: "contact Name 1"
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  },
  {
    _accountId: "5beee0966d17bc42501f1235",
    name: "Company Name 2",
    contactEmail: "email2@email.com",
    contactName: "contact Name 2"
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  }
]

```

I am collecting this data from the following two models:

**Warranty**

```
{
  _id: "5beee0966d17bc42501f5086",
  jobsiteAddressStreet: String,
  jobsiteAddressCity: String,
  jobsiteAddressState" String,
  jobsiteAddressZip: Number,
  warrantyFee: Number,
  _accountId: {
    type: Schema.Types.ObjectId,
    ref: "accounts"
  },
  payStatus: String
}

```

**Account**

```
{
  _id: "5beee0966d17bc42501f1235",
  name: String,
  contactName: String,
  contactEmail: String
}

```

My current query is the following:

```
Warranty.aggregate([
    {
      $match: {
        payStatus: "Invoiced Next Billing Cycle"
      }
    },
    {
      $group: {
        _id: "$_accountId",
        total: {
          $sum: "$warrantyFee"
        },
        lineItems: {
          $push: {
            _id: "$_id",
            jobsiteAddress: {
              $concat: [
                "$jobsiteAddressStreet",
                " ",
                "$jobsiteAddressCity",
                ", ",
                "$jobsiteAddressState",
                " ",
                "$jobsiteAddressZip"
              ]
            },
            warrantyFee: "$warrantyFee"
          }
        }
      }
    },
    {
      $project: {
        reason: "Warranties",
        total: "$total",
        lineItems: "$lineItems"
      }
    }
  ])
    .then(warranties => {
      console.log(warranties);
      Account.populate(warranties, {
        path: "_id",
        select: "contactName contactEmail name"
      })
        .then(warranties => {
          res.send(warranties);
        })
        .catch(err => {
          res.status(422).send(err);
          throw err;
        });
    })
    .catch(err => {
      res.status(422).send(err);
      throw err;
    });

```

Which results in the following:

```
[
  {
    _id: {
      _id: "5bc39dfa331c0e2cb897b61e",
      name: "Company Name 1",
      contactEmail: "email1@email.com",
      contactName: "Contact Name 1"
    },
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  },
  {
    _id: {
      _id: "5bc39dfa331c0e2cb897b61e",
      name: "Company Name 2",
      contactEmail: "email2@email.com",
      contactName: "Contact Name 2"
    },
    reason: "Warranties",
    total: 1152,
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ]
  }
]

```

As you can see this is really close with some minor issues.

1. It shows \_id instead of \_accountId. I defaulted to this because whenever I try to return the \_accountId in $group it labels it as a non-accumulator field and when I do it in $project it just doesn't show up. The data sets must be grouped by the \_accountId in the Warranty model.
2. I would prefer to add the additional (contactName, contactEmail, name) fields to the top level object instead of creating a subdocument if possible. This may be simple or impossible as I am not super familiar with populate but can't find anything to answer my question directly.

The goal at the end of this is to take the returned object and use the array of objects to do a bulk create of documents to another collection.

-- Answer to my specific use case --

```
Warranty.aggregate([
    {
      $match: {
        payStatus: "Invoiced Next Billing Cycle"
      }
    },
    {
      $group: {
        _id: "$_accountId",
        total: {
          $sum: "$warrantyFee"
        },
        lineItems: {
          $push: {
            _id: "$_id",
            jobsiteAddress: {
              $concat: [
                "$jobsiteAddressStreet",
                " ",
                "$jobsiteAddressCity",
                ", ",
                "$jobsiteAddressState",
                " ",
                "$jobsiteAddressZip"
              ]
            },
            warrantyFee: "$warrantyFee"
          }
        }
      }
    },
    {
      $lookup: {
        from: Account.collection.name,
        localField: "_id",
        foreignField: "_id",
        as: "accounts"
      }
    },
    {
      $unwind: "$accounts"
    },
    {
      $project: {
        lineItems: "$lineItems",
        reason: "Warranties",
        total: "$total",
        type: "Invoice",
        date: new Date(),
        company: "$accounts.name",
        contactName: "$accounts.contactName",
        contactEmail: "$accounts.contactEmail"
      }
    },
    {
      $addFields: {
        _accountId: "$_id"
      }
    },
    {
      $project: {
        _id: 0
      }
    }
  ])

```

This gives me the result:

```
[
  {
    lineItems: [
      {
        _id: "5be203eb3afd8098d4988152",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ],
    reason: "Warranties",
    total: 384,
    type: "Invoice",
    date: "2018-11-21T14:08:15.052Z",
    company: "Company Name 1",
    contactName: "Contact Name 1",
    contactEmail: "email1@email.com",
    _accountId: "5be203eb3afd8098d4988152",
    referenceNumber: 1542809296615
  },
  {
    lineItems: [
      {
        _id: "5beee0966d17bc42501f5086",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf43929e7179a56e21382bc",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      },
      {
        _id: "5bf4392fe7179a56e21382bd",
        jobsiteAddress: "1234 Street Southwest Sunnyville, Wyoming 12345",
        warrantyFee: 384
      }
    ],
    reason: "Warranties",
    total: 1152,
    type: "Invoice",
    date: "2018-11-21T14:08:15.052Z",
    company: "Company Name 2",
    contactName: "Contact Name 2",
    contactEmail: "email2@email.com",
    _accountId: "5bc39dfa331c0e2cb897b61e",
    referenceNumber: 1542809295680
  }
]

```