Query Mongodb using condition from previous field defined via $first - mongodb

Question

Trying to total a documents by a condition where timestamp equals the first timestamp found
Need to sum the number of documents that meet the condition that the document matched the first timestamp value found. Below is what I've tried in order to reference the timestamp equal to { "$first": "$timestamp" }
IP.aggregate([
{
"$sort":{'timestamp':-1}
},
{
"$group": {
"_id": "$application",
"url": { "$first": "$app_url_name" },
"timestamp": { "$first": "$timestamp" },
"total": {
$sum: {
$cond: {
if: {
$and:[
{$eq: ['$environment_category', 'PROD']},
{$eq: ['$timestamp', '$_id.timestamp']}
]
},
then: 1,
else: 0
}
}
},
"enabled": { $sum: {$cond: {if: {
$and: [
{$eq: ['$availability', 'available']},
{$eq: ['$state', 'enabled']},
{$eq: ['$environment_category', 'PROD']}
]
} ,
then: 1,
else: 0} }}
}
},

Answer 1

Here's the solution:
db.ips.aggregate([
{
"$sort": { "timestamp": -1 }
},
{
"$group": {
"_id": "$application",
"doc": { "$first": "$$ROOT" },
"items": {"$push": "$$ROOT"}
}
},
{
"$project": {
"_id": 0,
"application": "$_id",
"timestamp": "$doc.timestamp",
"items": {
"$filter": {
"input": "$items",
"as": "item",
"cond": { "$eq": [ "$$item.timestamp", "$doc.timestamp" ] }
}
}
}
},
]);