Count ocurrence of two fields - mongodb-aggregation

Question

I have this kind of documents in a MongoDb collection:
[
{
"_id": {
"id": 892,
"answer": "C",
"level": "regular"
},
"total": 4
},
{
"_id": {
"id": 891,
"answer": "Regular",
"level": "neutral"
},
"total": 3
},
{
"_id": {
"id": 892,
"answer": "B",
"level": "regular"
},
"total": 3
},
{
"_id": {
"id": 891,
"answer": "Ótimo",
"level": "positive"
},
"total": 5
},
{
"_id": {
"id": 892,
"answer": "E",
"level": "regular"
},
"total": 3
},
{
"_id": {
"id": 891,
"answer": "Bom",
"level": "positive"
},
"total": 1
},
{
"_id": {
"id": 891,
"answer": "Ruim",
"level": "negative"
},
"total": 2
},
{
"_id": {
"id": 892,
"answer": "D",
"level": "regular"
},
"total": 3
},
{
"_id": {
"id": 891,
"answer": "Péssimo",
"level": "negative"
},
"total": 3
},
{
"_id": {
"id": 892,
"answer": "F",
"level": "regular"
},
"total": 1
}
]
I'm trying to count answer and level ocurrences using MongoDb aggregation pipiline. I'm expecting some output like this:
[
{
"id": 891,
"answers": [
{
"answer": "Ótimo",
"count": 5
},
{
"answer": "Bom",
"count": 1
},
{
"answer": "Regular",
"count": 3
},
{
"answer": "Ruim",
"count": 2
},
{
"answer": "Péssimo",
"count": 3
}
],
"levels": [
{
"level": "positive",
"count": 6
},
{
"level": "neutral",
"count": 3
},
{
"level": "negative",
"count": 5
}
],
"total": 14
},
{
"id": 892,
"answers": [
{
"answer": "B",
"count": 3
},
{
"answer": "C",
"count": 4
},
{
"answer": "D",
"count": 3
},
{
"answer": "E",
"count": 3
},
{
"answer": "F",
"count": 1
},
],
"levels": [
{
"level": "regular",
"count": 14
}
],
"total": 14
}
]
How could I achieve the desired output using MongoDb aggregation pipeline?
EDIT: Actually I'm already using $group to achieve something like that, but I guess only one $group step on the pipeline will not achieve the desired output. Here is my current $group step:
{
$group: {
_id: {
id: "$_id.id"
},
answers: {
$push: {
answer: "$_id.answer",
count: "$count"
}
},
levels: {
$push: {
level: "$_id.level",
count: "$count"
}
},
total: { $sum: "$count" }
}
}
Here is the output I have so far:
[
{
"_id": {
"id": 892
},
"answers": [
{
"answer": "F",
"count": 1
},
{
"answer": "D",
"count": 3
},
{
"answer": "E",
"count": 3
},
{
"answer": "C",
"count": 4
},
{
"answer": "B",
"count": 3
}
],
"levels": [
{
"level": "regular"
},
{
"level": "regular"
},
{
"level": "regular"
},
{
"level": "regular"
},
{
"level": "regular"
}
]
},
{
"_id": {
"id": 891
},
"answers": [
{
"answer": "Ruim",
"count": 2
},
{
"answer": "Péssimo",
"count": 3
},
{
"answer": "Bom",
"count": 1
},
{
"answer": "Regular",
"count": 3
},
{
"answer": "Ótimo",
"count": 5
}
],
"levels": [
{
"level": "negative"
},
{
"level": "negative"
},
{
"level": "positive"
},
{
"level": "neutral"
},
{
"level": "positive"
}
]
}
]

Answer 1

The following aggregation pipeline:
{ $group: {
_id: { id: "$_id.id" },
answers: {
$push: {
answer: "$_id.answer",
level: "$_id.level",
count: "$total"
}
},
levels: {
$push: {
level: "$_id.level",
count: "$total"
}
}
}},
{ $unwind: $levels },
{ $group: {
_id: {
id: "$_id.id",
level: "$levels.level"
},
answers: { $addToSet: "$answers" },
total: { $sum: "$levels.count" }
}},
{ $group: {
_id: { id: "$_id.id" },
answers: { $addToSet: "$answers" },
levels: {
$push: {
level: "$_id.level",
count: "$total"
}
},
total: { $sum: "$total" }
}},
{ $project: {
_id: 0,
id: "$_id.id",
answers: 1,
levels: 1,
total: 1
}}
Will produce the desired output.