Mongoose aggreagate with group not working - node.js

Question

In my Node.JS API, it is possible to order and get menus. The structure of an ordered menu looks like the following (the main schema is the orderMenuSchema; menuItemSchema is for the subdocument-array with ordered items):
var menuItemSchema = mongoose.Schema({
itemId: {
type: mongoose.Schema.Types.ObjectId,
required: true
},
prepared: {
type: Boolean,
default: false
},
finished: {
type: Boolean,
default: false
},
timestamp: {
type: Date,
default: Date()
}
}, {_id: false})
var orderMenuSchema = mongoose.Schema({
orderId: {
type: mongoose.Schema.Types.ObjectId,
required: true
},
menuId: {
type: mongoose.Schema.Types.ObjectId,
required: true
},
items: {
type: [menuItemSchema],
required: true,
validate: menuItemsCheck
},
finished: {
type: Boolean,
default: false
},
timestamp: {
type: Date,
default: Date()
}
})
Example Data:
{
"_id":"5d2333a1841a0e4ef05873d0",
"finished":false,
"timestamp":"2019-07-08T12:14:04.000Z",
"menuId":"5d189ffdbe02ef0b00b22370",
"items":[
{
"prepared":false,
"finished":false,
"timestamp":"2019-07-08T12:14:04.000Z",
"itemId":"5d189ffdbe02ef0b00b2236d"
},
{
"prepared":false,
"finished":false,
"timestamp":"2019-07-08T12:14:04.000Z",
"itemId":"5d189ffdbe02ef0b00b2236e"
},
{
"prepared":false,
"finished":false,
"timestamp":"2019-07-08T12:14:04.000Z",
"itemId":"5d189ffdbe02ef0b00b2236f"
}
],
"orderId":"5d2333a1841a0e4ef05873c3",
"__v":0
}
Whether an item is prepared or not is stored in the prepared field of the menuItem.
Each menu has multiple items to choose from, and the user is able to have only some items - that's why the orderMenuSchema has an array of subdocuments called "items" in which only the ordered items are stored.
Now I would like to get all unprepared menus, group them by the menuID
and then group them by the itemID - everything with a Mongoose
aggregation.
So, I think I need two groupings: The first one by the menuId, the second one by the itemId.
Furthermore, I would like to know how many of each item are unprepared - so after grouping by the menuId, I need to get a count of all unprepared items
Expected Output:
I thought of something like this:
{
"result":[
{
"menuID":"tastefulMenu123",
"items":[
{
"itemId":"noodlesoop123",
"unpreparedCount":13
},
{
"itemId":"tastyBurger123",
"unpreparedCount":2
},
{
"itemId":"icecoldIce123",
"unpreparedCount":20
}
]
}
]
}
There will be an array of subdocuments, one subdocument for each menuId. Each subdocument than has an array of items in which the itemID as well as the unpreparedCount are stored.
What I already tried (not working):
OrderMenu.aggregate([
{$unwind: "$items"},
{ $project: { prepared: 1, itemId: 1} },
{ $match: {
prepared: false,
timestamp: {
$gte: today,
$lt: tomorrow
}
}},
{ $group: {
_id: {menuId: '$menuId', itemId: '$itemId'},
count: { $sum: 1 }
}}
]).then(result => {
console.log(result)
return Promise.resolve(result)
}).catch(error => {
console.log(error)
return Promise.reject(500)
})
Any help would be appreciated!