How can i aggregate filter nested documents and get value from other field

For this you should use the aggregation framework of mongo db, because will require complex operations to get the data in the shape that you want.

https://www.mongodb.com/docs/manual/aggregation/

Every aggregation is an array of stages and every stage does something specific.

I used the next stages:

1. addFields: Allows you to add new fields to the response of every document, so if you don't have group in the document, that will add or replace it.
2. project: Allows you remove some fields of a document. In a projection stage if you set an attribute as 0 that will remove that attribute from the response.

Also I used some operators:

1. filter: this allows you to filter data of an element that is an array
2. arrayElemenAt: receives an array and return the position specified

The pipeline:

[
   {
      "$addFields":{
         "group":{
            "$arrayElemAt":[
               {
                  "$filter":{
                     "input":"$look",
                     "as":"item",
                     "cond":{
                        "$eq":[
                           "$$item.art",
                           "group-id"
                        ]
                     }
                  }
               },
               0
            ]
         },
         "called":{
            "$arrayElemAt":[
               {
                  "$filter":{
                     "input":"$look",
                     "as":"item",
                     "cond":{
                        "$eq":[
                           "$$item.art",
                           "called"
                        ]
                     }
                  }
               },
               0
            ]
         },
         "accessTime":{
            "$arrayElemAt":[
               {
                  "$filter":{
                     "input":"$look",
                     "as":"item",
                     "cond":{
                        "$eq":[
                           "$$item.art",
                           "access-time"
                        ]
                     }
                  }
               },
               0
            ]
         },
         "rate":{
            "$arrayElemAt":[
               {
                  "$filter":{
                     "input":"$answer",
                     "as":"item",
                     "cond":{
                        "$eq":[
                           "$$item.art",
                           "rate-id"
                        ]
                     }
                  }
               },
               0
            ]
         },
         "protocol":{
            "$arrayElemAt":[
               {
                  "$filter":{
                     "input":"$answer",
                     "as":"item",
                     "cond":{
                        "$eq":[
                           "$$item.art",
                           "protocol"
                        ]
                     }
                  }
               },
               0
            ]
         }
      }
   },
   {
      "$addFields":{
         "group":"$group.data",
         "called":"$called.data",
         "accessTime":"$accessTime.data",
         "rate":"$rate.data",
         "protocol":"$protocol.data"
      }
   },
   {
      "$project":{
         "look":0,
         "answer":0
      }
   }
]

This is quite cumbersome with the current structure, as for each field you have to convert the object to an array, filter it then convert it back, here's how it looks:

db.collection.aggregate([
  {
    $replaceRoot: {
      newRoot: {
        "$mergeObjects": [
          {
            _id: "$_id",
            name: "$name",
            profile: "$profile",
            date: "$date",
            
          },
          {
            "$arrayToObject": {
              $map: {
                input: {
                  $filter: {
                    input: {
                      $objectToArray: {
                        $ifNull: [
                          {
                            "$arrayElemAt": [
                              {
                                $filter: {
                                  input: {
                                    $ifNull: [
                                      "$look",
                                      []
                                    ]
                                  },
                                  cond: {
                                    $eq: [
                                      "$$this.art",
                                      "group-id"
                                    ]
                                  }
                                }
                              },
                              0
                            ]
                          },
                          {
                            art: ""
                          }
                        ]
                      }
                    },
                    cond: {
                      $eq: [
                        "$$this.k",
                        "data"
                      ]
                    }
                  }
                },
                in: {
                  k: "goup",
                  v: "$$this.v"
                }
              }
            }
          },
          {
            "$arrayToObject": {
              $map: {
                input: {
                  $filter: {
                    input: {
                      $objectToArray: {
                        $ifNull: [
                          {
                            "$arrayElemAt": [
                              {
                                $filter: {
                                  input: {
                                    $ifNull: [
                                      "$look",
                                      []
                                    ]
                                  },
                                  cond: {
                                    $eq: [
                                      "$$this.art",
                                      "called"
                                    ]
                                  }
                                }
                              },
                              0
                            ]
                          },
                          {
                            art: ""
                          }
                        ]
                      }
                    },
                    cond: {
                      $eq: [
                        "$$this.k",
                        "data"
                      ]
                    }
                  }
                },
                in: {
                  k: "called",
                  v: "$$this.v"
                }
              }
            }
          },
          {
            "$arrayToObject": {
              $map: {
                input: {
                  $filter: {
                    input: {
                      $objectToArray: {
                        $ifNull: [
                          {
                            "$arrayElemAt": [
                              {
                                $filter: {
                                  input: {
                                    $ifNull: [
                                      "$look",
                                      []
                                    ]
                                  },
                                  cond: {
                                    $eq: [
                                      "$$this.art",
                                      "access-time"
                                    ]
                                  }
                                }
                              },
                              0
                            ]
                          },
                          {
                            art: ""
                          }
                        ]
                      }
                    },
                    cond: {
                      $eq: [
                        "$$this.k",
                        "data"
                      ]
                    }
                  }
                },
                in: {
                  k: "access-time",
                  v: "$$this.v"
                }
              }
            }
          },
          {
            "$arrayToObject": {
              $map: {
                input: {
                  $filter: {
                    input: {
                      $objectToArray: {
                        $ifNull: [
                          {
                            "$arrayElemAt": [
                              {
                                $filter: {
                                  input: {
                                    $ifNull: [
                                      "$answer",
                                      []
                                    ]
                                  },
                                  cond: {
                                    $eq: [
                                      "$$this.art",
                                      "rate-id"
                                    ]
                                  }
                                }
                              },
                              0
                            ]
                          },
                          {
                            art: ""
                          }
                        ]
                      }
                    },
                    cond: {
                      $eq: [
                        "$$this.k",
                        "data"
                      ]
                    }
                  }
                },
                in: {
                  k: "rate",
                  v: "$$this.v"
                }
              }
            }
          },
          {
            "$arrayToObject": {
              $map: {
                input: {
                  $filter: {
                    input: {
                      $objectToArray: {
                        $ifNull: [
                          {
                            "$arrayElemAt": [
                              {
                                $filter: {
                                  input: {
                                    $ifNull: [
                                      "$answer",
                                      []
                                    ]
                                  },
                                  cond: {
                                    $eq: [
                                      "$$this.art",
                                      "protocol"
                                    ]
                                  }
                                }
                              },
                              0
                            ]
                          },
                          {
                            art: ""
                          }
                        ]
                      }
                    },
                    cond: {
                      $eq: [
                        "$$this.k",
                        "data"
                      ]
                    }
                  }
                },
                in: {
                  k: "protocol",
                  v: "$$this.v"
                }
              }
            }
          }
        ]
      }
    }
  }
])

Mongo Playground

If you're using Mongo version 5+, then you can use $getField to simplify the syntax a little bit, here's how one field would look like in this syntax:

goup: {
    $getField: {
        field: 'data',
        input: {
            '$arrayElemAt': [
                {
                    $filter: {
                        input: {
                            $ifNull: [
                                '$look',
                                [],
                            ],
                        },
                        cond: {
                            $eq: [
                                '$$this.art',
                                'group-id',
                            ],
                        },
                    },
                },
                0,
            ],
        },
    },
},

You would require an aggregate operation that has a pipeline with the following key operators and stages:

• $map: an operator to transform the look and answer arrays into documents with just mapped k and v fields, crucial for obtaining a hash map with the following operator
• $arrayToObject: this allows the above to be possible i.e. converting an array into a single document
• $mergeObjects: combine top level fields i.e. _id, date, name, profile together with the converted documents above
• $replaceWith: pipeline stage to replace the root document with the specified document from above

Overall, your pipeline should follow:

const first = { 
   $first: {
      $split: ['$$this.art', '-']
   }
};
const keyExpression = {
   $cond: [
     { $eq: [first, 'access'] },
     'accessTime',
     first
   ]
};

const pipeline = [
    { $replaceWith: {
        $mergeObjects: [
            {  
                _id: '$_id', 
                date: '$date', 
                name: '$name', 
                profile: '$profile',
                protocol: '',
                group: '',
                called: '',
                rate: '',
                accessTime: '',
            },
            { $arrayToObject: {
                $map: {
                  input: '$look',
                  in: { k: keyExpression, v: '$$this.data' } 
                }
            } },
            { $arrayToObject: {
                $map: {
                  input: '$answer',
                  in: { k: keyExpression, v: '$$this.data' } 
                }
            } }
        ]
    } } 
]

Mongo Playground