Add new object inside array of objects, inside array of objects in mongodb - arrays

Question

Considering the below bad model, as I am totally new to this.
{
"uid": "some-id",
"database": {
"name": "nameOfDatabase",
"collection": [
{
"name": "nameOfCollection",
"fields": {
"0": "field_1",
"1": "field_2"
}
},
{
"name": "nameOfAnotherCollection",
"fields": {
"0": "field_1"
}
}
]
}
}
I have the collection name (i.e database.collection.name) and I have a few fields to add to it or delete from it (there are some already existing ones under database.collection.fields, I want to add new ones or delete exiting ones).
In short how do I update/delete "fields", when I have the database name and the collection name.
I cannot figure out how to use positional operator $ in this context.
Using mongoose update as
Model.update(conditions, updates, options, callback);
I don't know what are correct conditions and correct updates parameters.
So far I have unsuccessfully used the below for model.update
conditions = {
"uid": req.body.uid,
"database.name": "test",
"database.collection":{ $elemMatch:{"name":req.body.collection.name}}
};
updates = {
$set: {
"fields": req.body.collection.fields
}
};
---------------------------------------------------------
conditions = {
"uid": req.body.uid,
"database.name": "test",
"database.collection.$.name":req.body.collection.name
};
updates = {
$addToSet: {
"fields": req.body.collection.fields
}
};
I tried a lot more but none did work, as I am totally new.
I am getting confused between $push, $set, $addToSet, what to use what not to?, how to?
The original schema is supposed to be as show below, but running queries on it is getting harder n harder.
{
"uid": "some-id",
"database": [
{ //array of database objects
"name": "nameOfDatabase",
"collection": [ //array of collection objects inside respective databases
{
"name": "nameOfCollection",
"fields": { //fields inside a this particular collection
"0": "field_1",
"1": "field_2"
}
}
]
}
]
}