Add field to nested subdocument where value depends on boolean condition

I have a collection like this:

[
  {
    "name": "Orange",
    "variants": [
      {
        "color": "orange",
        "props": []
      }
    ]
  },
  {
    "name": "Banana",
    "variants": [
      {
        "color": "green",
        "props": [
          {
            "uid": 1,
            "grade": 3
          },
          {
            "uid": 2,
            "grade": 5
          },
          {
            "uid": 3,
            "grade": 7
          }
        ]
      }
    ]
  }
]

available_props = [1,2]

Now I would like to add to every prop in props in every variant a field available which evaluates if the uid of the respective prop is in available_props.

Desired outcome:

[
  {
    "name": "Orange",
    "variants": [
      {
        "color": "orange",
        "props": []
      }
    ]
  },
  {
    "name": "Banana",
    "variants": [
      {
        "color": "green",
        "props": [
          {
            "uid": 1,
            "grade": 3,
            "available": true
          },
          {
            "uid": 2,
            "grade": 5,
            "available": true
          },
          {
            "uid": 3,
            "grade": 7,
            "available": false
          }
        ]
      }
    ]
  }
]

Thanks for your help!

you could use nested $maps combined with $mergeObjects

db.collection.aggregate([
  {
    $addFields: {
      variants: {
        $map: {
          input: "$variants",
          as: "variant",
          in: {
            $mergeObjects: [
              "$$variant",
              {
                props: {
                  $map: {
                    input: "$$variant.props",
                    as: "prop",
                    in: {
                      $mergeObjects: [
                        "$$prop",
                        {
                          available: { $in: [ "$$prop.uid", [ 1, 2 ] ] }
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
])

as a tip if you are familiar with JS you could come up with almost similar logic
js Array.prototype.map -> mongo $map
js spread operator(...) -> mongo $mergeObjects
js Array.prototype.includes -> mongo $in

const doc =   {
    "name": "Banana",
    "variants": [
      {
        "color": "green",
        "props": [
          {
            "uid": 1,
            "grade": 3,
            "available": true
          },
          {
            "uid": 2,
            "grade": 5,
            "available": true
          },
          {
            "uid": 3,
            "grade": 7,
            "available": false
          }
        ]
      }
    ]
  }
  
  
const newDoc = {
  ...doc,
  variants: doc.variants.map(variant => ({
    ...variant,
    props: variant.props.map(prop => ({
      ...prop,
      available: [1, 2].includes(prop.uid)
    }))
  }))
}

console.log(newDoc)