How to get conditional fields in Mongodb

Question

Hello good developers,

I am new to MongoDB and trying to fetch conditional data for my requirements.

I have the following collection:

 [
{
    "id":10001,
    "name":"Test 1",
    "status":"live",
    "traffics":[
        {
            "id":"1a3s5d435a4sd",
            "status":"",
        },
        {
            "id":"1a3s5d44as54d35a4sd",
            "status":"CMP",
        },
        {
            "id":"a3s5d454asd34asd",
            "status":"",
        },
        {
            "id":"1a35sd45a4sd34asd3",
            "status":"TERM",
        },
        {
            "id":"as35d435a4sd354as3d43asd4",
            "status":"CMP",
        },
        {
            "id":"135as4d5a4sd354a3s5d43asd",
            "status":"CMP",
        },
        {
            "id":"123as1d31a3d12ads13as",
            "status":"TERM",
        }
    ]

},
{...},{...}
]

I want to get data like these

ID, Name, count traffics as Starts, count (traffics where status = "CMP") as completes, count (traffics where status = "TERM") as Terminates, count (traffics where status = "") as Abandons

I am trying to run following command

db.inventory.aggregate( { $project: {id: 1, status: 1, starts: {$size: "$traffics"}, _id: 0}})

but I don't know how to get conditional data in there

Answer 1

I was able to modify @Yones answer a little bit so that I can get counts of the records based on conditions.

so here's my query for this.

db.collection.aggregate({
  $project: {
    id: 1,
    name: 1,
    status: 1,
    starts: {$size: "$traffics"},
    completes: {
        $size: {
            $filter: {
            input: "$traffics",
            as: "item",
            cond: {
                $eq: [
                    "$$item.status",
                    "CMP"
                    ]
                }
            }
        }
    },
    terminates: {
        $size: {
            $filter: {
            input: "$traffics",
            as: "item",
            cond: {
                $eq: [
                    "$$item.status",
                    "TERM"
                    ]
                }
            }
        }
    },
    abandons: {
        $size: {
            $filter: {
            input: "$traffics",
            as: "item",
            cond: {
                $eq: [
                    "$$item.status",
                    ""
                    ]
                }
            }
        }
    },
    _id: 0
  }
})

I am simply Filtering out the records based on my conditions using $filter

And then I am calculating its size using $size.

Here's working example for this answer: https://mongoplayground.net/p/TcuLlJShclA