JSONata - peek at each element to create/append to an array

Question

I'd like to transform the following json to the output Input:

{
  "firstName": "Jane",
  "personalHistory": {
    "hadmigraines": true,
    "hadmigraines4InAMonth": true,
    "hadheartDisease": true,
    "hadhighCholesterol": false
  }
}

Output:

{
  "oLifE": {
    "party": [
      {
        "person": {
          "firstName": "Jane"
        },
        "risk": {
          "medicalCondition": [
            {
              "conditionType": "MIGRAINE",
              "numberEpisodesTotal": 4,
              "frequency": "MONTHLY"
            },
            {
              "conditionType": "HEART_DISEASE"
            }
          ]
        }
      }
    ]
  }
}

I need to go through element by element in the personalHistory and add to the output medical array only if the hadxx condition is true. I am struggling with how to create/append to the medicalCondition array, as the person may not have any medical conditions. Please advise.

Answer 1

In order to write the code, you need to specify how the had... keys should be mapped to disease names and frequencies. But this snippet should get you started:

{
  "oLifE": {
    "party": [
      {
        "person": {
          "firstName": firstName
        },
        "risk": {
          /* iterate over each key value pair */
          "medicalCondition": $each(personalHistory, function($v, $k) {
              (
                /* strip had... */
                $k := $substring($k, 3);

                /* parse frequency */
                $parts := $split($k, /[0-9]/);

                $disease := $parts[0];
                $frequency := $parts[1];
                $number := $match($k, /[0-9]/).match;

                /* filter condition = true */
                $v ? {
                    "conditionType": $disease,
                    "numberEpisodesTotal": $number,
                    "frequency": $frequency = "InAMonth" ? "MONTHLY" : undefined
                } : undefined;
              )
            })
        }
      }
    ]
  }
}