CARP Web Service Plugin for Flutter

A Flutter library to access the CARP Web Service (CAWS) web API. This library is intended to be used with the carp_mobile_sensing framework, but also works on its own, if a app is to connect directly to CAWS.

For an overview of CARP and other Flutter CARP libraries, see CARP Mobile Sensing in Flutter.

Setup

You need a CARP Web Service (CAWS) host running. See the CARP Web Service GitHub repro and documentation for how to do this. If you're part of the CARP team, you can use the specified test, staging, and production servers.
Add carp_services as a dependency in your pubspec.yaml file.

This package uses the oidc plugin for authentication. Please follow their getting started guide and take a look at their example app.

Android

On Android you need to edit both the build.gradle file and the AndroidManifest.xml file plus disable some backup settings. You also need to add an activity to the AndroidManifest.xml to allow for redirection to/from the web view for authentication (if you are using the authenticate() method in the package). You manifest file would look something like this:

  ...

  <application
    android:name="${applicationName}"
    android:label="CAWS Example"
    android:fullBackupContent="@xml/backup_rules"
    android:dataExtractionRules="@xml/data_extraction_rules" 
    android:icon="@mipmap/ic_launcher">

  <!-- Used by authentication redirect to/from web view -->
  <activity
    android:name="net.openid.appauth.RedirectUriReceiverActivity"
    android:theme="@style/Theme.AppCompat.NoActionBar"
    android:exported="true"
    tools:node="replace">
    <intent-filter>
      <action android:name="android.intent.action.VIEW" />
      <category android:name="android.intent.category.DEFAULT" />
      <category android:name="android.intent.category.BROWSABLE" />
      <data android:scheme="carp-studies-auth" android:pathPrefix="/auth" />
    </intent-filter>
    <intent-filter>
      <action android:name="android.intent.action.VIEW" />
      <category android:name="android.intent.category.DEFAULT" />
      <category android:name="android.intent.category.BROWSABLE" />
      <data android:scheme="http" />
      <data android:host="carp.computerome.dk" />
      <data android:pathPrefix="/auth" />
    </intent-filter>
  </activity>

iOS

Add the following CFBundleURLTypes entry in your Info.plist file:

<key>CFBundleURLTypes</key>
<array>
    <dict>
        <key>CFBundleTypeRole</key>
        <string>Editor</string>
        <key>CFBundleURLSchemes</key>
        <array>
            <string>com.my.app</string>
        </array>
    </dict>
</array>

Replace com.my.app with your application id.

Services

CARP Web Services (CAWS) consists of a set of sub-services, which are accessible for the client:

CarpAuthService - authentication service for CAWS
CarpParticipationService - CAWS-specific implementation of the ParticipationService
CarpDeploymentService - CAWS-specific implementation of the DeploymentService
CarpDataStreamService - CAWS-specific implementation of the DataStreamService
CarpService - resource management (folders, documents, and files) and alternative data management service

The CarpParticipationService, CarpDeploymentService, and CarpDataStreamService follows the CARP Core architecture, and are CAWS-specific implementations of the ParticipationService, DeploymentService, and DataStreamService, respectively. TheCarpAuthService and CarpService are only part of the CAWS architecture ("non-core" endpoints).

Configuration

All CAWS services needs to be configured before used, using the configure method taking a CarpApp configuration.

// The URI of the CAWS server to connect to.
final Uri uri = Uri(
  scheme: 'https',
  host: 'dev.carp.dk',
);

final CarpApp app = CarpApp(
  name: "CAWS @ DTU [DEV]",
  uri: uri,
);

// Configure the CARP Service with this app.
CarpService().configure(app);

The singleton can now be accessed via CarpService().

Any service can be configured based on another service, like this:

CarpParticipationService().configureFrom(CarpService());

Authentication Service

Authentication is done using the CarpAuthService singleton, which is configured using the CarpAuthProperties properties:

// The authentication configuration
late CarpAuthProperties authProperties = CarpAuthProperties(
  authURL: uri,
  clientId: 'studies-app',
  redirectURI: Uri.parse('carp-studies-auth://auth'),
  // For authentication at CAWS the path is '/auth/realms/Carp'
  discoveryURL: uri.replace(pathSegments: [
    'auth',
    'realms',
    'Carp',
  ]),
);

await CarpAuthService().configure(authProperties);

Basic authentication is using the CAWS Keycloak login page, which the system opens when running:

CarpUser user = await CarpAuthService().authenticate();

This CarpUser object contains the OAuth token in the token (of type OAuthToken) parameter. Since the CarpUser object can be serialized to JSON, the user and the (valid) OAuth token can be stored on the phone.

To refresh the OAuth token the client (Flutter) simply call:

await CarpAuthService().refresh()

This method returns a CarpUser, with a new access token.

To authenticate using username and password without opening the web view, use the authenticateWithUsernamePassword method:

CarpUser user = await CarpAuthService().authenticateWithUsernamePassword('username', 'password');

To log out, just call the logout or logoutNoContext methods:

await CarpAuthService().logout()

Deployments

A core notion of CARP is the Deployment subsystem, which has two services:

Participation Service - allows retrieving participation information for study deployments, and managing data related to participants which is input by users.
Deployment Service - allows for retrieving primary device deployments for participating primary devices as defined in the study protocol.

Participation Service

Enables the client to get invitations for a specific accountId, i.e. a user. Default is the user who is authenticated to the CARP Service.

// We assume that we are authenticated to CAWS and that the CarpService() 
// instance has been configured.

// configure from another CAWS service
CarpParticipationService().configureFrom(CarpService());

// get invitations for this account (user)
List<ActiveParticipationInvitation> invitations =
    await CarpParticipationService().getActiveParticipationInvitations();

There is also support for showing a modal UI dialog for the user to select amongst several invitations. This is done using the getStudyInvitation method, like this:

var invitation =
    await CarpParticipationService().getStudyInvitation(context);

The invitation holds information on the study deployment. So, once you (or the user) has selected an invitation, you can let the CAWS services know about the deployment by using the setInvitation method:

CarpParticipationService().setInvitation(invitation);

The participant service also handles the collection of "participant data", which are specified in the StudyProtocol (as expectedParticipantData).

You can get and set participation data like this:

// Get participant data for a deployment with id [deploymentId].
final data = await CarpParticipationService().getParticipantData(deploymentId);

// Set participant data for a deployment with id [deploymentId].
// When role name is not specified, this data is set for the entire deployment.
await CarpParticipationService().setParticipantData(
  testDeploymentId,
  {
    AddressInput.type: AddressInput(
      address1: 'DTU HealthTech',
      address2: 'Technical University of Denmark',
      street: 'Ørsteds Plads',
      city: 'Kgs. Lyngby',
      postalCode: 'DK-2800',
      country: 'Denmark',
    )
  },
);

However, a more convenient way to handle participant data is to use a ParticipationReference, which can be obtained from the CarpParticipationService singleton.

ParticipationReference participation = CarpParticipationService().participation();

A ParticipationReference can now be used to set and get participant data, including the more specialized "Informed Consent" data type:

// The following example is from a family deployment with a father, mother, and child.

// Get all participant data for this deployment
ParticipantData data = await participation.getParticipantData();

// Set the address of the deployment (i.e., the family)
data = await participation.setParticipantData(
  {
    AddressInput.type: AddressInput(
      address1: 'Peder Bangs Vej 3',
      city: 'Kgs. Lyngby',
      postalCode: 'DK-2800',
      country: 'Denmark',
    )
  },
);

// Set role-specific data (sex of the father)
final data = await participation.setParticipantData(
  {SexInput.type: SexInput(value: Sex.Male)},
  father,
);

// Set the informed consent for a user (father)
await participation.setInformedConsent(
  InformedConsentInput(
    userId: 'ec44c84d-3acd-45d5-83ef-1511e0c39e48',
    name: father,
    consent: 'I agree!',
    signatureImage: 'blob',
  ),
  father,
);

// Get the informed consent for all role names in this deployment
Map<String, InformedConsentInput?> consent = await participation.getInformedConsent();

// Remove the informed consent for a user (father)
await participation.removeInformedConsent(father);

Deployment Service

The Deployment Service handles "deployment" configurations, i.e. configurations that describe how data sampling in a study should take place.

The CarpDeploymentService has methods for getting deployments and for updating deployment and device status. Here are a list of examples:

// We assume that we are authenticated to CAWS and that the CarpService() 
// instance has been configured.

CarpDeploymentService().configureFrom(CarpService());

// Get the deployment status.
StudyDeploymentStatus status = await CarpDeploymentService()
    .getStudyDeploymentStatus(deploymentId);

// Register the primary device for the deployment.
await CarpDeploymentService().registerDevice(
    deploymentId,
    status.primaryDeviceStatus!.device.roleName,
    DefaultDeviceRegistration(deviceDisplayName: 'Samsung A10'));

// Get the deployment describing what data to collect.
PrimaryDeviceDeployment deployment = await CarpDeploymentService().getDeviceDeploymentFor(
  deploymentId,
  status.primaryDeviceStatus!.device.roleName,
);

// Mark the deployment as successfully deployed on this device.
await CarpDeploymentService().deviceDeployed(
  deploymentId,
  status.primaryDeviceStatus!.device.roleName,
  deployment.lastUpdatedOn,
);

However, instead of keeping track of deployment IDs, a more convenient way to access deployments are to use a DeploymentReference:

// We assume that we are authenticated to CAWS, that the CarpService() 
// instance has been configured, and that the deployment information has 
// be saved by setting the invitation (using the 'setInvitation' method).

CarpDeploymentService().configureFrom(CarpService());

// get a deployment reference to the invited deployment
final deploymentReference = CarpDeploymentService().deployment();

// get the status of this deployment
var status = await deploymentReference.getStatus();

// register a device
status = await deploymentReference.registerDevice(
    status.primaryDeviceStatus!.device.roleName,
    DefaultDeviceRegistration(deviceDisplayName: 'Samsung A10'));

// get the primary device deployment
var deployment = await deploymentReference.get();

// mark the deployment as a successfully deployed
status = await deploymentReference.deployed();

Data Stream Service

Collected data is streamed back to a CARP Web Service using the Data subsystem. This is done using the CarpDataStreamService like this:

// Configure a [CarpDataStreamService] from an existing CAWS service.
CarpDataStreamService().configureFrom(CarpService());

// Create a (very simple) data batch with one measurement to upload
var measurement = Measurement(
  sensorStartTime: 1642505144000000,
  data: Geolocation(
      latitude: 55.680802203873114, longitude: 12.581802212861367));

var batch = [
  DataStreamBatch(
    dataStream: DataStreamId(
        studyDeploymentId:
            CarpDataStreamService().app.studyDeploymentId ?? '',
        deviceRoleName: 'smartphone',
        dataType: Geolocation.dataType),
    firstSequenceId: 0,
    measurements: [measurement],
    triggerIds: {0}),
];

// Get a data stream and append the batch
CarpDataStreamService().stream().append(batch);

However, you would rarely need to use these endpoints in your app, since the carp_backend would handle this when you use a CarpDataEndPoint as the data endpoint in the study protocol.

CARP Web Service

The CarpService provides access to a set of "non-core" endpoints in CAWS. These "non-core" endpoints are:

JSON Documents organized in Collections
File Management
Informed Consent Documents
Data Points

All of these endpoints can be considered as additional "resources" which are available for up- or download from clients.

Collections of JSON Documents

CARP Web Service supports storing JSON documents in nested collections.

A CollectionReference is used to access collections and a DocumentReference is used to access documents. Both of these can be used to:

creating, updating, and deleting documents
accessing documents in collections

// access a document
//  - if the document id is not specified, a new document (with a new id)
//    is created
//  - if the collection ('users') don't exist, it is created
DocumentSnapshot document = await CarpService()
    .collection('users')
    .document()
    .setData({'email': username, 'name': 'Administrator'});

// update the document
DocumentSnapshot updatedDocument = await CarpService()
    .collection('/users')
    .document(document.name)
    .updateData({'email': username, 'name': 'Super User'});

// get the document
DocumentSnapshot newDocument =
    await CarpService().collection('users').document(document.name).get();

// get the document by its unique ID
newDocument = await CarpService().documentById(document.id).get();

// delete the document
await CarpService().collection('users').document(document.name).delete();

// get all collections from a document
List<String> collections = newDocument.collections;

// get all documents in a collection.
List<DocumentSnapshot> documents =
    await CarpService().collection('users').documents;

File Management

CARP Web Service supports storing raw binary file.

A FileStorageReference is used to manage files and have methods for:

uploading a file
downloading a file
getting a file object
getting all file objects
deleting a file

When uploading a file, you can add metadata as a Map<String, String>.

// first upload a file
final File uploadFile = File('test/img.jpg');
final FileUploadTask uploadTask = CarpService()
    .getFileStorageReference()
    .upload(uploadFile, {
  'content-type': 'image/jpg',
  'content-language': 'en',
  'activity': 'test'
});
CarpFileResponse response = await uploadTask.onComplete;
int id = response.id;

// then get its description back from the server
final CarpFileResponse result =
    await CarpService().getFileStorageReference(id).get();

// then download the file again
// note that a local file to download is needed
final File downloadFile = File('test/img-$id.jpg');
final FileDownloadTask downloadTask =
    CarpService().getFileStorageReference(id).download(downloadFile);
int responseCode = await downloadTask.onComplete;

// now get references to ALL files in this study
final List<CarpFileResponse> results =
    await CarpService().getFileStorageReference(id).getAll();

// finally, delete the file
responseCode = await CarpService().getFileStorageReference(id).delete();

NOTE: This is an old endpoint which is deprecated. Informed consent should be uploaded as a "participant data" as outlined above. However, at the moment, CAWS supports both types of informed consent (for backward compatibility reasons).

A ConsentDocument can be uploaded and downloaded to and from CAWS.

try {
  ConsentDocument uploaded = await CarpService().createConsentDocument({
    'text': 'The original terms text.',
    'signature': 'Image Blob',
  });

  ConsentDocument downloaded =
      await CarpService().getConsentDocument(uploaded.id);
} catch (error) {
  ...;
}

Data Points

NOTE: This is an old endpoint which is deprecated. Data should be uploaded using "data streams" as outlined above. However, at the moment, CAWS supports both types of data upload (for backward compatibility reasons).

A DataPointReference is used to manage DataPoint objects on a CARP Web Service, and have CRUD methods for:

post a data point
batch upload multiple data points
get a data point
delete data points

// Create a piece of data
final lightData = AmbientLight(
  maxLux: 12,
  meanLux: 23,
  minLux: 0.3,
  stdLux: 0.4,
);

// create a CARP data point
final data = DataPoint.fromData(lightData);

// post it to the CARP server, which returns the ID of the data point
int dataPointId =
    await CarpService().getDataPointReference().postDataPoint(data);

// get the data point back from the server
CARPDataPoint dataPoint =
    await CarpService().getDataPointReference().getDataPoint(dataPointId);

// batch upload a list of raw json data points in a file
final File file = File('test/batch.json');
await CarpService().getDataPointReference().batchPostDataPoint(file);

// delete the data point
await CarpService().getDataPointReference().deleteDataPoint(dataPointId);

Features and bugs

Please file feature requests and bug reports at the issue tracker.

License

This software is copyright (c) the Technical University of Denmark (DTU). This software is made available 'as-is' in a MIT license.

CARP Web Service Plugin for Flutter

Setup

Android

iOS

Services

Configuration

Authentication Service

Deployments

Participation Service

Deployment Service

Data Stream Service

CARP Web Service

Collections of JSON Documents

File Management

Data Points

Features and bugs

License

Libraries

carp_webservices package

CARP Web Service Plugin for Flutter

Setup

Android

iOS

Services

Configuration

Authentication Service

Deployments

Participation Service

Deployment Service

Data Stream Service

CARP Web Service

Collections of JSON Documents

File Management

Informed Consent Document

Data Points

Features and bugs

License

Libraries

carp_webservices package