// Request authorization to access HealthKit.
    func requestAuthorization() {
        // Requesting authorization.
        /// - Tag: RequestAuthorization
        
        let writeDataTypes: Set<HKSampleType> = dataTypesToWrite()
        let readDataTypes: Set<HKObjectType> = dataTypesToRead()
    <span class="pl-c"><span class="pl-c">//</span> requset authorization</span>

        healthStore.requestAuthorization(toShare: writeDataTypes, read: readDataTypes) { (success, error) in

if !success {

// Handle the error here.

            } else {
            DispatchQueue.<span class="pl-smi">main</span>.<span class="pl-smi">async</span> {
                <span class="pl-c1">self</span>.<span class="pl-smi">authorizedHK</span> <span class="pl-k">=</span> <span class="pl-c1">true</span>
            }
            
        }
    }
}</pre></div>

Where healthStore is the object of HKHealthStore().
The HKHealthStore is like the database of healthdata in iOS.
dataTypesToWrite and dataTypesToRead are the object we would like to query in the database.
The authorization need a purpose and this is done in the Info.plist xml file by adding:
    <key>NSHealthClinicalHealthRecordsShareUsageDescription</key>
    <string>Read data for IrisExporter</string>
    <key>NSHealthShareUsageDescription</key>
    <string>Send data to IRIS</string>
    <key>NSHealthUpdateUsageDescription</key>
    <string>Write date for IrisExporter</string>

How to connect to a FHIR Repository
For this part I used the FHIR package from Smart-On-FHIR : https://github.com/smart-on-fhir/Swift-FHIR
The class used is the FHIROpenServer.
    private func test() {
    progress <span class="pl-k">=</span> <span class="pl-c1">true</span>
    
    <span class="pl-k">let</span> url <span class="pl-k">=</span> <span class="pl-c1">URL</span>(<span class="pl-c1">string</span>: <span class="pl-c1">self</span>.<span class="pl-c1">url</span>)

    swiftIrisManager.<span class="pl-smi">fhirServer</span> <span class="pl-k">=</span> <span class="pl-c1">FHIROpenServer</span>(<span class="pl-c1">baseURL</span> : url<span class="pl-k">!</span> , <span class="pl-c1">auth</span>: <span class="pl-c1">nil</span>)
    
    swiftIrisManager.<span class="pl-smi">fhirServer</span>.<span class="pl-c1">getCapabilityStatement</span>() { FHIRError <span class="pl-k">in</span>
        
        progress <span class="pl-k">=</span> <span class="pl-c1">false</span>
        showingPopup <span class="pl-k">=</span> <span class="pl-c1">true</span>
        
        <span class="pl-k">if</span> FHIRError <span class="pl-k">==</span> <span class="pl-c1">nil</span> {
            showingSuccess <span class="pl-k">=</span> <span class="pl-c1">true</span>
            textSuccess <span class="pl-k">=</span> <span class="pl-s"><span class="pl-pds">"</span>Connected to the fhir repository<span class="pl-pds">"</span></span>
        } <span class="pl-k">else</span> {
            textError <span class="pl-k">=</span> FHIRError<span class="pl-k">?</span>.<span class="pl-c1">description</span> <span class="pl-k">??</span> <span class="pl-s"><span class="pl-pds">"</span>Unknow error<span class="pl-pds">"</span></span>
            showingSuccess <span class="pl-k">=</span> <span class="pl-c1">false</span>
        }
        
        <span class="pl-k">return</span>
    }

}</pre></div>

This create a new object fhirServer in the singleton swiftIrisManager.
Next we use the getCapabilityStatement()
If we can retrieve the capabilityStatement of the FHIR server this mean we successfully connected to the FHIR repository.
This repository is not in HTTPS, by default apple bock this kind of communication.
To allow HTTP support, the Info.plist xml file is edited like this:
    <key>NSAppTransportSecurity</key>
    <dict>
        <key>NSExceptionDomains</key>
        <dict>
            <key>localhost</key>
            <dict>
                <key>NSIncludesSubdomains</key>
                <true/>
                <key>NSExceptionAllowsInsecureHTTPLoads</key>
                <true/>
            </dict>
        </dict>
    </dict>

How to save a patient in the FHIR Repository
Basic operation by first checking if the patient already exists in the repository
Patient.search(["family": "\(self.lastName)"]).perform(fhirServer)
This search for patient with the same family name.
Here we can imaging other scenarios like with Oauth2 and JWT token to join the patientid and his token. But for this demo we keep things simple.
Next if the patient exist, we retrieve it, otherwise we create the patient :
    func createPatient(callback: @escaping (Patient?, Error?) -> Void) {
        // Create the new patient resource
        let patient = Patient.createPatient(given: firstName, family: lastName, dateOfBirth: birthDay, gender: gender)
    patient<span class="pl-k">?</span>.<span class="pl-c1">create</span>(fhirServer, <span class="pl-c1">callback</span>: { (error) <span class="pl-k">in</span>
        <span class="pl-c1">callback</span>(patient, error)
    })
}</pre></div>


How to extract data from the HealthKit
It's done by querying the healthkit Store (HKHealthStore())
Here we are querying for footsteps.
Prepare the query with the predicate.
        //Last week
        let startDate = swiftFhirIrisManager.startDate
        //Now
        let endDate = swiftFhirIrisManager.endDate
    <span class="pl-c1">print</span>(<span class="pl-s"><span class="pl-pds">"</span>Collecting workouts between <span class="pl-pse">\(</span><span class="pl-s1">startDate</span><span class="pl-pse"><span class="pl-s1">)</span></span> and <span class="pl-pse">\(</span><span class="pl-s1">endDate</span><span class="pl-pse"><span class="pl-s1">)</span></span><span class="pl-pds">"</span></span>)

    <span class="pl-k">let</span> predicate <span class="pl-k">=</span> HKQuery.<span class="pl-c1">predicateForSamples</span>(<span class="pl-c1">withStart</span>: startDate, <span class="pl-c1">end</span>: endDate, <span class="pl-c1">options</span>: HKQueryOptions.<span class="pl-smi">strictEndDate</span>)</pre></div>

Then the query itself with his type of data (HKQuantityType.quantityType(forIdentifier: .stepCount)) and the predicate.
func queryStepCount(){
    <span class="pl-c"><span class="pl-c">//</span>Last week</span>

        let startDate = swiftFhirIrisManager.startDate

//Now

        let endDate = swiftFhirIrisManager.endDate
    <span class="pl-c1">print</span>(<span class="pl-s"><span class="pl-pds">"</span>Collecting workouts between <span class="pl-pse">\(</span><span class="pl-s1">startDate</span><span class="pl-pse"><span class="pl-s1">)</span></span> and <span class="pl-pse">\(</span><span class="pl-s1">endDate</span><span class="pl-pse"><span class="pl-s1">)</span></span><span class="pl-pds">"</span></span>)

    <span class="pl-k">let</span> predicate <span class="pl-k">=</span> HKQuery.<span class="pl-c1">predicateForSamples</span>(<span class="pl-c1">withStart</span>: startDate, <span class="pl-c1">end</span>: endDate, <span class="pl-c1">options</span>: HKQueryOptions.<span class="pl-smi">strictEndDate</span>)

    <span class="pl-k">let</span> query <span class="pl-k">=</span> <span class="pl-c1">HKSampleQuery</span>(<span class="pl-c1">sampleType</span>: HKQuantityType.<span class="pl-c1">quantityType</span>(<span class="pl-c1">forIdentifier</span>: .<span class="pl-smi">stepCount</span>)<span class="pl-k">!</span>, <span class="pl-c1">predicate</span>: predicate, <span class="pl-c1">limit</span>: HKObjectQueryNoLimit, <span class="pl-c1">sortDescriptors</span>: <span class="pl-c1">nil</span>) { (query, results, error) <span class="pl-k">in</span>
        
        <span class="pl-k">guard</span> <span class="pl-k">let</span> results <span class="pl-k">=</span> results <span class="pl-k">as?</span> [HKQuantitySample] <span class="pl-k">else</span> {
               <span class="pl-k">return</span>
        }
   
        <span class="pl-c1">process</span>(results, <span class="pl-c1">type</span>: .<span class="pl-smi">stepCount</span>)
    
    }

    healthStore.<span class="pl-c1">execute</span>(query)

}</pre></div>


How to transform HealthKit data to FHIR
For this part, we use the Microsoft package HealthKitToFHIR
https://github.com/microsoft/healthkit-to-fhir
This is a usefull package that offer factories to transform HKQuantitySample to FHIR Observation
     let observation = try! ObservationFactory().observation(from: item)
      let patientReference = try! Reference(json: ["reference" : "Patient/\(patientId)"])
      observation.category = try! [CodeableConcept(json: [
          "coding": [
            [
              "system": "http://terminology.hl7.org/CodeSystem/observation-category",
              "code": "activity",
              "display": "Activity"
            ]
          ]
      ])]
      observation.subject = patientReference
      observation.status = .final
      print(observation)
      observation.create(self.fhirServer,callback: { (error) in
          if error != nil {
              completion(error)
          }
      })
Where item is an HKQuantitySample in our case a stepCount type.
The factory does most of the job of converting 'unit' and 'type' to FHIR codeableConcept and 'value' to FHIR valueQuantity.
The reference to the patientId is done manually by casting a json fhir reference.
let patientReference = try! Reference(json: ["reference" : "Patient/\(patientId)"])
Same is done for the category :
      observation.category = try! [CodeableConcept(json: [
          "coding": [
            [
              "system": "http://terminology.hl7.org/CodeSystem/observation-category",
              "code": "activity",
              "display": "Activity"
            ]
          ]
      ])]
At last the observation is created in the fhir repository :
      observation.create(self.fhirServer,callback: { (error) in
          if error != nil {
              completion(error)
          }
      })

Backend (FHIR)
Not much to say, it's based on the fhir template form the InterSystems community :
https://openexchange.intersystems.com/package/iris-fhir-template

Frontend
It's based on Henrique works who is a nice front end for FHIR repositories made in jquery.
https://openexchange.intersystems.com/package/iris-fhir-portal

ToDos

[ ] add more code comments
[ ] handle patient name