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React Native Exposure Notification Service

React Native Exposure Notification Service is a react native module, which provides a common interface to Apple/Google's Exposure Notification APIs.

For more on contact tracing see:

Contents

Getting started

To integrate with your react-native app:

# with npm
npm install --save react-native-exposure-notification-service

# with yarn
yarn add react-native-exposure-notification-service

Mostly automatic installation

React Native Exposure Notifications uses autolinking to allow your project discover and use this code.

On Android there are no further steps.

CocoaPods on iOS needs this extra step:

cd ios && pod install && cd ..

Usage

There are multiple ways to use the React Native Exposure Notification Service in your React application. You can use it directly via the ExposureNotificationModule and manage the application state yourself, or you can use the ExposureProvider React Context implementation, where the application state is managed for you.

ExposureNotificationModule

Example

import ExposureNotificationModule from 'react-native-exposure-notification-service';

ExposureNotificationModule.start();

Methods

canSupport()
const canSupport = await ExposureNotificationModule.canSupport();

Used to check if the device can support the relevant exposure notification API. This returns a promise that resolves a boolean determining if the device can support tracing or not.

isSupported()

exposure api is available on the device.

const supported = await ExposureNotificationModule.isSupported();

Used to check if the device has the contact tracing APIs installed. This returns a promise that resolves with true if contact tracing is supported.

exposureEnabled()
const enabled = await ExposureNotificationModule.exposureEnabled();

Use to check if the contact tracing is enabled. This returns a promise that resolves with true if contact tracing is enabled.

Note: On android, if enabled is true, tracing has started.

isAuthorised()
const authorised = await ExposureNotificationModule.isAuthorised();

Use to check if the user has authorised contact tracing. Calling this method will NOT trigger an authorisation request. This returns a promise that resolves with a string representing the current authorisation state and can be one of: granted, denied, blocked, unavailable or unknown

authoriseExposure()
const authorised = await ExposureNotificationModule.authoriseExposure();

Use to trigger an authorisation dialogue. This returns a promise that resolves with true if the user has authorised contact tracing, if they denied the request then false is returned.

configure()
ExposureNotificationModule.configure(options);

Use to configure the module. This method is synchronous, and should be called before start etc. It takes an options object as a parameter with the following properties:

  • exposureCheckFrequency: a number representing the period between exposure downloads in minutes
  • serverURL: a string representing the the server api url (should not have trailing /)
  • keyServerUrl: a string representing the the key server api url (should not have trailing /). Will default to serverURL
  • keyServerType: a string representing the the key server type, options are nearform or google. Defaults to nearform
  • authToken: a string representing the current authorization token
  • refreshToken: a string representing a token used to refresh the authorization token
  • storeExposuresFor: a number representing the number of days to store data for
  • notificationTitle: a string representing the title for positive exposure notifications popup,
  • notificationDesc: a string representing the description for positive exposure notifications popup,
  • callbackNumber: a string representing the phone number of a user if opted into automatic callback on positive exposure notification,
  • analyticsOptin: a boolean representing whether the user opted in or not
  • hideForeground: Android only. a boolean representing whether to hide foreground notifications
start()
const started = await ExposureNotificationModule.start();

Use to start exposure notifications. This method should only be called when canSupport(), isSupported() and isAuthorised() all return/resolve positive values and after configure() has been called.

A promise is returned and will resolve to true after a successful start, otherwise it will resolve to false.

status()
const status = await ExposureNotificationModule.status();

Used to get the current start status. This method returns a promise that resolves to a map containing 2 keys state and type both with string values.

The state can return as active, disabled, unavailable or unknown, and if set to disabled will contain the type presenting the reason why.

The type can return as bluetooth, exposure, resolution, paused, starting and its meaning should be read in combination with state, i.e. a state of disabled and a type of bluetooth indicates that ENS is disabled because bluetooth is off.

State changes also trigger the event onStatusChanged.

stop()
ExposureNotificationModule.stop();

Used to stop contact tracing and all scheduled tasks. Exposure notifications must be authorised again after this method is called.

pause()
ExposureNotificationModule.pause();

Used to pause contact tracing. Use start() to unpause.

deleteAllData()
const result = await ExposureNotificationModule.deleteAllData();

Used to delete all app related data including config & exposure data. This returns a promise that resolves true if all data is successfully removed.

deleteExposureData()
const result = await ExposureNotificationModule.deleteExposureData();

Used to deletes exposure data but leaves configuration data intact. This returns a promise that resolves true if exposure data is successfully removed.

getDiagnosisKeys()
const keys = await ExposureNotificationModule.getDiagnosisKeys();

Used to retrieve a devices own diagnosis keys (typically all keys before today within a 14 day window). This returns a promise that resolves to an array of maps containing the key keyData, encoded as a base64 string. This key should be used in export files for exposure matching. If the user denies the request, the returned promise will reject.

Note: this will trigger a dialog from the underlying exposure notifications API, requesting permission from the device user.

checkExposure()
ExposureNotificationModule.checkExposure();

Used to manually check exposure during testing. Typically checkExposure is performed in background on schedule specified in configure. This facilitates an immediate check.

On successful matches, this will raise a notification to the user, and also raise an exposure event to the app

simulateExposure()
ExposureNotificationModule.simulateExposure();

Used to manually generate an exposure alert during testing to make it easier to validate UX flows around exposure events.

This will raise a notification to the user, and also raise an exposure event to the app.

getCloseContacts()
const contacts = await ExposureNotificationModule.getCloseContacts();

Used to retrieve the summary array of matches recorded. This async function returns a promise that resolves to a array of maps with the following keys:

  • exposureAlertDate
  • attenuationDurations
  • daysSinceLastExposure
  • matchedKeyCount
  • maxRiskScore
  • summationRiskScore
triggerUpdate() (Android Only)
const result = await ExposureNotificationModule.triggerUpdate();

Used to trigger play services update should the user be using a version older than 201817017

Enabling background processing (iOS only)

Enable exposure checks when the app is backgrounded / closed.

Prerequites:

Go to Signing & Capabilities -> Background Modes, tick Background fetch & Background processing.

Add a new item to the Info.plist and choose "Permitted background task scheduler identifiers"
Expand the array and add value $(PRODUCT_BUNDLE_IDENTIFIER).exposure-notification

You should see the following lines in your Info.plist:

	<key>UIBackgroundModes</key>
	<array>
		<string>fetch</string>
		<string>processing</string>
	</array>
	<key>BGTaskSchedulerPermittedIdentifiers</key>
	<array>
		<string>$(PRODUCT_BUNDLE_IDENTIFIER).exposure-notification</string>
	</array>

Add the following header in AppDelegate.m

#import <react_native_exposure_notification_service-Swift.h>

Add the following lines in application:didFinishLaunchingWithOptions:

// Register the background task to perform exposure checks
[ExposureNotificationModule registerBackgroundProcessing];

Subscribing to Events

Create an emitter object using the ExposureNotificationModule

import {NativeEventEmitter} from 'react-native';
import ExposureNotificationModule from 'react-native-exposure-notification-service';
const emitter = new NativeEventEmitter(ExposureNotificationModule);

In a component or custom hook, you could use an effect to subscribe to the native module's events as follows:

useEffect(() => {
  function handleEvent(ev) {
    if (ev.exposure) {
      console.log(
        'You have come in contact with someone diagnosed with COVID-19'
      );
    }

    // handle other events...
  }

  const subscription = emitter.addListener('exposureEvent', handleEvent);

  return () => {
    subscription.remove();
    emitter.removeListener('exposureEvent', handleEvent);
  };
}, []);

There are two major events:

  1. exposure: fires when an exposure match event happens, which could be used to update the UI (contains a string)
  2. onStatusChange: fires when the exposure tracing status changes. This event is a map map containing 2 keys state and type both with string values.

When exposure fires, getCloseContacts() would typically be called to retrieve the summary information.

When onStatusChange fires, it will contain the same data returned from a call to status()

Note: Other events may fire, depending on the platform and whether debug/release. These are mostly for debug and error logging only and should not be used for triggering application logic.

ExposureProvider

You should add ExposureProvider in your app root component.

Example

import {
  ExposureProvider,
  useExposure
} from 'react-native-exposure-notification-service';

function Root() {
  return (
    <ExposureProvider
      traceConfiguration={{
        exposureCheckInterval: 180,
        storeExposuresFor: 14,
      }
      serverUrl="https://your.exposure.api/api"
      keyServerUrl="https://your.exposure.api/api"
      keyServerType=KeyServerType.nearform
      authToken="your-api-auth-token"
      refreshToken="your-api-refresh-token"
      notificationTitle="Close contact detected"
      notificationDescription="Open the app for instructions">
      notificationRepeat=0>
      <App />
    </ExposureProvider>
  );
}

Props

isReady

boolean (default false) If true, will start the exposure notification service if the user has given permission

traceConfiguration (required)

object Tracing related configuration options

{
  exposureCheckInterval: number;
  storeExposuresFor: number;
}
appVersion (required)

string The build version of your application

serverUrl (required)

string The URL of your exposure API

authToken (required)

string The auth token for your exposure API

refreshToken (required)

string The refresh token for your exposure API

notificationTitle (required)

string The title of a close contact push notification

notificationDescription (required)

string The description of a close contact push notification

callbackNumber (optional)

string The phone number to be used for health authority callbacks

analyticsOptin (optional)

boolean (default false) Consent to send analytics to your exposure API's /metrics endpoint

notificationRepeat (optional)

number (default 0) Used to repeat exposure notifications after set interval. Internal time is in minutes.

certList (optional)

string (default ``) Used to override the cert names to be looked for in the package on android.

useExposure

Use the useExposure hook in any component to consume the ExposureProvider context & methods

Example

import {useExposure} from 'react-native-exposure-notification-service';

function MyComponent() {
  const {status, permissions, requestPermissions} = useExposure();

  return (
    <View>
      <Text>Exposure status: {status}</Text>
      <Text>Exposure permissions: {JSON.stringify(permissions, null, 2)}</Text>
      <Button onPress={requestPermissions}>Ask for exposure permissions</Button>
    </View>
  );
}

Values

All of these values are available on the return value of useExposure

status

Status The current status of the exposure service

supported

boolean The exposure API is available on the device.

canSupport

boolean This device can support the exposure API

isAuthorised

boolean The user has authorised the exposure API

enabled

boolean The exposure API is enabled & has started

contacts

CloseContact[] | null An array of recorded matches

initialised

boolean The native module has successfully initialised

permissions

ExposurePermissions The current status of permissions for exposure & notifications

start()

() => void

Start the exposure API, check & update the status & check for close contacts

Calls ExposureNotificationModule.start()

stop()

() => void

Stop the exposure API & check & update status

Calls ExposureNotificationModule.stop()

configure()

() => void

Configure the native module (this is called internally once permissions have been granted)

Calls ExposureNotificationModule.configure()

checkExposure()

(skipTimeCheck: boolean) => void

Calls ExposureNotificationModule.checkExposure()

getDiagnosisKeys()

() => Promise<any[]>

Calls ExposureNotificationModule.getDiagnosisKeys()

exposureEnabled()

() => Promise<boolean>

Calls ExposureNotificationModule.exposureEnabled()

authoriseExposure()

() => Promise<boolean>

Calls ExposureNotificationModule.authoriseExposure()

deleteAllData()

() => Promise<void>

Calls ExposureNotificationModule.deleteAllData() & checks & update the status

supportsExposureApi()

() => Promise<void>

Manually check whether the device supports the exposure API and update the context

cancelNotifications()

() => void

Used to cancel any repeating notifications that have been scheduled

getCloseContacts()

() => Promise<CloseContact[] | null>

Manually retrieve a summary of matched records and update the context

Calls ExposureNotificationModule.getCloseContacts()

getLogData()

() => Promise<{[key: string]: any}>

Get log data from the exposure API

Calls ExposureNotificationModule.getLogData()

triggerUpdate()

() => Promise<string | undefined>

Triggers a play services update on Android if possible

Calls ExposureNotificationModule.triggerUpdate()

deleteExposureData()

() => Promise<void>

Deletes exposure data & updates the context

Calls ExposureNotificationModule.deleteExposureData()

readPermissions()

() => Promise<void>

Checks the current status of exposure and notifications permissions and updates the context

askPermissions()

() => Promise<void>

Requests permissions from the user for exposure and notifications permissions and updates the context

getVersion()

() => Promise<Version>

Returns the version number for the app

getBundleId()

() => Promise<string>

Returns the bundle identifier / package name for the app

getConfigData()

() => Promise<{[key: string]: any}>

Returns the config being used by the module

setExposureState()

(setStateAction: SetStateAction<State>) => void

Not recommended: Manually update the state in the exposure context. Can be useful for development & simulating different states.

Test Application

A test application to run the methods above, can be found under the test-app folder.

To run this, from the terminal:

  • cd test-app
  • yarn
  • yarn start
  • and in a separate terminal window yarn android or yarn ios

Typically, it is better to run the test application on a device rather than a simulator.

Note: The check exposure function will not succeed unless connected to a valid server, if you have access to a valid server, modify ./test-app/config.js with your settings.

To debug in android you will need to generate a debug keystore file, from the terminal execute:

cd android/app

then

keytool -genkey -v -keystore debug.keystore -storepass android -alias androiddebugkey -keypass android -keyalg RSA -keysize 2048 -validity 10000

cd ../..

Caveats

When building/running an app using the native module, several issues can arise.

Android

Google Play Services (Exposure Notifications)

The Exposure Notification API provided by Google uses the Nearby API installed with Google Play Services.

This API is being rolled out by Google so that as many devices as possible support the API.

The minimum android version required is 23 (marshmallow).

The application performs a test to determine if the required API is available on the device using the isSupported() method. If it is not installed google play services must be updated with the Nearby API.

If you have trouble with this, try triggerUpdate() to see if Play Services can be updated or update manually.

Applications using the Exposure API should be government agencies, and so not all applications can access the API directly.

Minify

If using minify when building an .apk on android, classes are often obfuscated, in which case some errors can arise when using reflection.

To keep required classes from being obfuscated, edit you proguard-rules.pro and add the following keep rules

-keep public class com.horcrux.svg.** {*;}
-keep class com.google.crypto.tink.** { *; }
-keep class net.sqlcipher.** { *; }
-keep class net.sqlcipher.database.* { *; }
-keep class * extends androidx.room.RoomDatabase
-keep class * extends com.google.auto
-keep class org.checkerframework.checker.nullness.qual.** { *; }

iOS

Common

Reloading the Native Module

If you make changes to the native module, and are referencing the package in your project, you may need to re-install it occasionally. You can do this by pointing at a different commit, branch or version in your package.json.

You can link to commit using #<commit> at the end of the git reference, or add #<feature>\/<branch> or if versioning use, #semver:<semver> (if the repo has any tags or refs matching that range). If none of these are specified, then the master branch is used.

eg.

{
  "dependencies": {
    "react-native-exposure-notification": "git+https://github.com/covidgreen/react-native-exposure-notification.git#semver:^1.0"
  }
}

If you are developing and make changes to a branch, and are not seeing changes being reflected in your react-native app, you can try reinstall the module as follows:

yarn remove react-native-exposure-notification && yarn add git+https://github.com/covidgreen/react-native-exposure-notification.git`

You can also link to the module directly on your file system if developing locally:

yarn add file:<path-to-module>`

Server Connectivity for Diagnosis Key Uploads and Exposure Notifications

In order to upload/download diagnosis keys for exposure notifications, an applications using this module needs to connect to a server that accepts upload of tokens, and packages them into valid export zip files.

Team

Lead Maintainers

Core Team

Contributors

Past Contributors

  • TBD
  • TBD

Hosted By

Linux Foundation Public Health

Acknowledgements

License

Copyright (c) 2020 Health Service Executive (HSE) Copyright (c) The COVID Green Contributors

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

[http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

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