React V2.1.X

Introduction

SDK overview

Welcome to the Flagship ReactJS SDK documentation!

The following documentation helps you to run Flagship on your ReactJS environment (client-side or server-side).

Flagship ReactJS SDK provides a <FlagshipProvider />, which makes Flagship features available to the rest of your app.
Flagship features are accessible using Flagship hooks, have a look at the documentation for details.

Feel free to contact us if you have any questions regarding this documentation.

SDK features

This SDK version helps you:

Set a visitor ID
Update visitor context
Assign campaigns via the Decision API or via the Bucketing
Get modifications
Activate campaigns
Send hits to our Universal Collect

Prerequisites

Node.js: version 6.0.0 or later
Npm: version 5.2.0 or later
React: version 16.8.0 or later (the SDK only supports hooks for now)

Good to know

Changelog

Visible on Github

Getting started

Initialization

There are four steps to follow to get started with the React Flagship SDK.

Install the node module

npm install @flagship.io/react-sdk

Import the Flagship React provider

In most cases, do this in your App.js file to wrap your entire app with the provider.

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider>{/* [...] */}</FlagshipProvider>
  </>
);

Initialize the provider

You must at least include the required props like envId, apiKey, visitorData.

NOTE: apiKey is not required for now but will be in next major release!

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY" // <= Required in next major release
      visitorData={{
        id: "YOUR_VISITOR_ID",
        context: {
          // some context
        },
        isAuthenticated: false,
      }}
      enableConsoleLogs={true}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

Use a Flagship hook in a component

In most case, you will get the desired modifications.

import React from "react";
import { useFsModifications } from "@flagship.io/react-sdk";

export const MyReactComponent = () => {
  const fsModifications = useFsModifications([
    {
      key: "backgroundColor",
      defaultValue: "green",
      activate: true,
    },
  ]);
  return (
    <div
      style={{
        height: "200px",
        width: "200px",
        backgroundColor: fsModifications.backgroundColor,
      }}
    >
      {"I'm a square with color=" + fsModifications.backgroundColor}
    </div>
  );
};

API Reference

`FlagshipProvider`

Here is the full list of props available to use inside the FlagshipProvider React component:

Props	Type	Default	Description
envId	string	Required	Your Flagship environment id.
visitorData	object	Required	This is the data to identify the current visitor using your app. See arguments
onInitStart	function():void	null	Callback function called when the SDK starts initialization.
onInitDone	function():void	null	Callback function called when the SDK ends initialization.
onUpdate	function(object):void	null	Callback function called when the SDK is updated. For example, after a synchronize is triggered or visitor context has changed. See arguments
onBucketingSuccess	function(object):void	null	Callback function called when the bucketing polling succeed. See arguments
onBucketingFail	function(object):void	null	Callback function called when the bucketing polling failed. See arguments
initialModifications	Array(object)	undefined	This is an array of modifications where each element must be same shape as the element inside the "campaigns" attribute. Providing this prop prevents the SDK from having an empty cache when it first initializes. If the shape of an element is not correct, an error log will give the reason why.
initialBucketing	Array(object)	undefined	This is an object of the data received when fetching bucketing endpoint. Providing this prop will make bucketing ready to use and the first polling will immediatly check for an update. If the shape of an element is not correct, an error log will give the reason why.
loadingComponent	React.ReactNode	undefined	This component will be rendered when Flagship is loading at first initialization only. By default, the value is undefined. It means it will display your app and it might display default modifications value for a very short moment.
fetchNow	boolean	true	`Decide to fetch automatically modifications when SDK is initialized.` NOTE: When `fetchNow=false` the property `loadingComponent` will be ignored. `fetchNow=false`
activateNow	boolean	false	Decide to trigger automatically the data when SDK is initialized. NOTE: when set to `true`, it will implicitly set `fetchNow=true` as well.
enableConsoleLogs	boolean	false	Enable it to display logs on the console when SDK is running. This will only display logs such as Warnings, Errors, Fatal errors and Info.
enableSafeMode	boolean	false	Enable it to run the SDK into a safe mode when an error might occurs through the SDK. When safe mode is triggered, default modifications will be returned and other function will just be executed without doing anything. NOTE: This feature is still experimental as it is currently catching errors globally (SDK + your app) which can gives side effects to your app. We're working on improvement.
enableCache	boolean	true	`Indicates wether enable or disable the client cache manager (local storage).` By enabling the cache, this will allow keep cross sessions visitor experience. Note: The cache is useful only when you do not specify a visitor id when creating a visitor. From there, you only need to be focus on handling the visitor context and whether it is authenticated or not. That's it.
enableErrorLayout	boolean	false	This is a small layout visible at the bottom of the screen. It is displayed only when an unexpected error occurred in the SDK. By default, it's set to false and if set to true , it will be only visible in a node environment other than production . Here a screenshot to have a look.
nodeEnv	string	'production'	If value is other than production , it will also display Debug logs.
flagshipApi	string	'https://decision-api.flagship.io/v1/'	This setting can be useful if you need to simulate the API for tests such as end-to-end or if you want to move to an earlier version of the Flagship API. Decision API V1 is set by default but deprecated, starting next version, only Decision API V2 will be implemnented.
apiKey	string	null	If you want to use the Decision API V2 , you must contact the support team so they'll provide you an API Key to authenticate the calls. You can find the api key of your environment on the Flagship dashboard, in Parameters > Environment & Security. NOTE: apiKey will be required in the next major release.
decisionMode	'API' \| 'Bucketing'	'API'	`Indicates the behavior of the SDK.` In `API` mode, it will get the modifications using the Flagship decision API. With `Bucketing`, it will load all campaigns once and compute the variation assignment of the visitor locally. Note: When `Bucketing` mode is set, you mustspecify `pollingInterval` attribute as well, so that bucketing can check for updates. Note2: When `Bucketing` mode is set, and the polling detects an update, it won't apply new changes until you manually trigger a campaign synchronization. Note3: Bucketing mode only works when you allow to start it during SDK initialization (`fetchNow=true`). We will add the ability to trigger it manually in the next minor release.
pollingInterval	number	null	Indicates the polling interval period in seconds when SDK is running Bucketing mode (`decisionMode="Bucketing"`). For example, if `pollingInterval=5`, a bucketing call will be trigger in background every 5 seconds. Note1: `pollingInterval` can't be lower than 1 second. Note2: if bucketing is enabled and `pollingInterval` value is `null`, the polling will be done once and an error log will be trigger.
timeout	number	2	Indicates the delay in seconds before it triggers a timeout when requesting campaigns via the Flagship decision api. Note: `timeout` can't be lower than 0 second.

📘
When bucketing is running (decisionMode="Bucketing"), the polling will restart its interval period based on the moment when one of the following props changes after first rendering :

envId

visitorData

initialModifications

initialBucketing

fetchNow

activateNow

enableConsoleLogs

nodeEnv

flagshipApi

apiKey

pollingInterval

visitorData

The visitorData object takes the following arguments:

Argument	Type	Description
id	string	Optional. Unique identifier for the current user. This can be an ID from your database or a session ID. Learn more NOTE: The visitor id must be a `string` and can't be a `number`. NOTE2: If you do not specify a value, the id will be either automatically generated or will be the visitor id from previous session (if `enableCache` equals `true`).
context	object	Optional. JSON object of key-value pairs describing the user and device context. Learn more
isAuthenticated	boolean	Optional. Indicates if the visitor is authenticated (true) or not (false, by default). NOTE: The SDK will listen the change of this value (switching from `true` to `false` or from `false` to `true`). This attribute is used for the experience continuity. Learn more

onUpdate

The onUpdate object has one argument with the following shape:

Key/Property	Description
fsModifications	Array or null. It contains the last modifications saved in cache. When `null`, it means the SDK still not ready. You can check the SDK status with other attributes.
config	Object. The current configuration running on the SDK.
status	Object. Contains informations about the actual SDK status. (Details below 👇)

status object shape:

Key/Property	Description
isLoading	Boolean. When `true`, the SDK is still not ready to render your App otherwise it'll use default modifications.
isSdkReady	Boolean. `true` after it has fully finished initialization tasks, `false` otherwise.
isVisitorDefined	Boolean. When `true` the flagship visitor instance is truthy, false otherwise.
hasError	Boolean. `true` when an error occured inside the SDK, `false` otherwise.
lastRefresh	String or null. The last update date occured on the flagship visitor instance.
firstInitSuccess	String or null. When `null` no initialization succeed yet. When `string` contains stringified date of last successful initialization.

onBucketingSuccess

The onBucketingSuccess object has one argument with the following shape:

Key/Property	Description
status	String. Returns either `200` (fresh update) or `304` (no change).
payload	Object. The latest bucketing data received.

onBucketingFail

The onBucketingFail object has one argument with the following shape:

Key/Property	Description
error	Object. Returns the error occurred and leads to bucketing polling failure.

`useFlagship`

Demo:

to get modifications
to synchronize campaigns
to send hits tracking

This is the most used hook from the Flagship React SDK. It gives further functionalities such as getting current modifications of your actual visitor, send hit tracking, SDK status...

Returns an object. (Typescript: UseFlagshipOutput)

`useFlagship input`

Argument	Type	Description
options	object	See description

`useFlagship input options`

Key/Property	Type	Description
modifications	object	Node param to specify Flagship modifications. See description

`useFlagship input options modifications`

Argument	Description
requested	Required. An array of objects for each modifications. See description
activateAll	Optional. The value is `false` by default

`useFlagship input options modifications requested`

Argument	Description
key	Required. The name of the modification.
defaultValue	Required. The default value if no value for this modification is found.
activate	Optional.

`useFlagship output`

Key/Property	Type	Description
modifications	object	An object where each key is a modification with corresponding value
getModificationInfo	function	Returns a promise with an object containing informations about modification matching the key specified in argument. See description
synchronizeModifications	function	Updates campaigns targeting that match the current visitor context. See description
hit	object	Gives you functions to send one or further hits. See description
status	object	Gives you information about SDK current state. See description
startBucketingPolling	function()	Call this function to start the bucketing manually. See description
stopBucketingPolling	function()	Call this function to stop the bucketing manually. See description

`useFlagship output getModificationInfo`

Full details here

Returns Promise<object | null>. (Typescript: GetModificationInfoOutput)

Argument	Type	Description
key	string	The modification key.

`useFlagship output synchronizeModifications`

Returns Promise<number>.

Full details here

Argument	Type	Default	Description
activateAllModifications	boolean	false	If set to `true`, all modifications will be activated. If set to `false` (default behavior), none will be activated.

`useFlagship output hits`

Key/Property	Description
send	Takes an object as parameter. The object must follow a hit shape.
sendMultiple	Takes an array of object as parameter. Each object must follow a hit shape. You can mix different hit shapes within the array.

`useFlagship output status`

Key/Property	Description
isLoading	If `true`, the SDK isn't ready.
lastRefresh	Date cast string with ISO format. This is the date corresponding to the most recent moment where modifications were saved in cache.

`useFlagship output startBucketingPolling`

Key/Property	Description
success	Boolean. If `true` means it succeed, `false` otherwise.
reason	String. A message telling the reason in case of failure.

`useFlagship output stopBucketingPolling`

Key/Property	Description
success	Boolean. If `true` means it succeed, `false` otherwise.
reason	String. A message telling the reason in case of failure.

`useFsModifications`

Demo:

to get modifications

The useFsModifications hook gives you the modifications saved in the SDK cache.

📘
If the SDK cache is empty, it will always return modification's default values.

Returns Flagship modifications. (Typescript: UseFsModificationsOutput)

`useFsModifications input`

Argument	Type	Default	Description
modificationsRequested	Array(object)	Required	List of all modifications you're looking for. See description
activateAllModifications	boolean	false	If set to true, all modifications will be activated. If set to false, none will be activated. NOTE: Setting this argument will override the `activate` attribute set in each element of the `modificationsRequested` array.

`useFsModifications input modificationsRequested`

Argument	Description
key	Required. The name of the modification.
defaultValue	Required. The default value if no value for this modification is found.
activate	Optional. Determines whether or not the modification is activated (if `activateAllModifications` is not set).

`useFsActivate`

Demo:

activating modifications

Returns void.

`useFsActivate input`

Argument	Type	Default	Description
modificationKeys	Array(string)	Required	An array of modification keys. For each key, a HTTP request will be sent to `activate` the corresponding modification.
applyEffectScope	Array(string)	[]	This argument behaves the same way as the second argument in the `React.useEffect` hook. It will listen for the array values and `synchronize` if it detects any changes. By default, it is triggered when the component where it's used is first rendered.

Getting modifications

with useFlagship hook (1/3)

Demo:

import { useFlagship } from "@flagship.io/react-sdk";

const fsParams = {
  modifications: {
    requested: [
      {
        key: "btnColor",
        defaultValue: "green",
        activate: true,
      },
    ],
  },
};

const {
  modifications: fsModifications,
  status: fsStatus,
  hit: fsHit,
} = useFlagship(fsParams);

with useFsModifications hook

Demo:

import { useFsModifications } from "@flagship.io/react-sdk";

const fsModifications = useFsModifications([
  {
    key: "btnColor",
    defaultValue: "green",
    activate: true,
  },
]);

Campaign synchronization

with useFlagship hook (2/3)

Demo:

import { useFlagship } from "@flagship.io/react-sdk";

const { synchronizeModifications } = useFlagship();

return (
  <>
    <Button
      onClick={() => {
        synchronizeModifications(activateAllModifications)
          .then((statusCode) => {
            if (statusCode < 300) {
              // Notify success...
            } else {
              // Notify failure...
            }
          })
          .catch((error) => {
            // Notify error...
          });
      }}
    >
      Trigger a synchronize
    </Button>
  </>
);

Campaign activation

with useFsActivate hook

Demo:

import { useFsActivate } from "@flagship.io/react-sdk";

const [toggle, setToggle] = React.useState(false);

useFsActivate(["btnColor", "otherKey1", "otherKey2"], [toggle]); // trigger an activate when "toggle" value change.

// insider render function:

<Button variant="secondary" onClick={() => setToggle(!toggle)}>
  Trigger activate
</Button>;

Experience continuity

It might happen that a visitor from your app is not yet recognized and is being authenticated (and recognized) later on...

From there, we provide the ability to ensure that during such transition, your visitor will keep same experience (meaning targetting still the same campaign's variations and thus same modifications).

In order to do a successful experience continuity, we will have to distinguish when the visitor is anonymous or authenticated.

Let's assume basic scenario to understand how things work:

Your visitor arrives on your app for the first time.

As this visitor will be considered as anonymous, we'll not specify a visitor id so that the SDK will a generate automatically one us. You can also specify some visitor context if necessary.

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY"
      visitorData={{
        id: null, // or remove this line
        context: {
          // some context
        },
        isAuthenticated: false, //
      }}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

Whatever how it has been set, the actual visitor id will be what we call its anonymous id.

📘
Be aware that when you do not specify a visitor id, as enableCache is enable by default, the SDK will try to find a previous visitor experience. If so, the new visitor will have the same visitor id as it was during the previous visitor session. From there, no id will be automatically generated.

Your visitor is signing in.

We need to set the value of visitorData.isAuthenticated to true.

Moreover, the visitor id set should be an existing visitor id (that has previously seen specific campaign's modifications) in order to make the experience continuity effective.

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY"
      visitorData={{
        id: "AUTHENTICATED_ID",
        context: {
          // some context
        },
        isAuthenticated: true,
      }}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

This new visitor id is what we call its authenticated id.

The visitor is updated as authenticated, keeping the previous variations from campaigns that are still matched and thus gives you same modifications as before being logged in.

📘
Keep in mind that if the visitor also has its context changed, you might still have changes on modifications as your visitor might target new campaigns.

Your visitor decide to sign out.

We need to set the value of visitorData.isAuthenticated back to false.

If you want to keep the same visitor (anonymous) experience as before, depending on the value of prop enableCache, you'll have to:

enableCache=true: the sdk will put back the previous anonymous id
automatically based on data from cache.

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY"
      visitorData={{
        id: null,
        context: {
          // some context
        },
        isAuthenticated: false, // <--- back to false
      }}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

enableCache=false: you should specify in prop, the same value as you set in step 1.

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY"
      visitorData={{
        id: "YOUR_VISITOR_ID", // <--- same value as step 1
        context: {
          // some context
        },
        isAuthenticated: false, // <--- back to false
      }}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

If you need a completly brand new visitor experience, you should put a new visitor id in visitorData.id prop instead:

import React from "react";
import { FlagshipProvider } from "@flagship.io/react-sdk";

const App = () => (
  <>
    <FlagshipProvider
      envId="YOUR_ENV_ID"
      apiKey="YOUR_API_KEY"
      visitorData={{
        id: "YOUR_BRAND_NEW_VISITOR_ID", // <--- new value
        context: {
          // some context
        },
        isAuthenticated: false, // <--- back to false
      }}
    >
      {/* [...] */}
    </FlagshipProvider>
  </>
);

Hit Tracking

This section helps you track your users in your application and learn how to build hits in order to feed campaign goals. For more information about our measurement protocol, read our Universal Collect documentation.

There are four different types of hits available:

Screen
Page
Transaction
Item
Event

with useFlagship hook (3/3)

Demo:

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

// insider render function:

<Button
  onClick={() => {
    const mockHit = {
      type: "Transaction",
      data: {
        transactionId: "12451342423",
        affiliation: "myAffiliation",
        totalRevenue: 999,
        shippingCost: 888,
        shippingMethod: "DHL",
        currency: "USD",
        taxes: 1234444,
        paymentMethod: "creditCard",
        itemCount: 2,
        couponCode: "myCOUPON",
        documentLocation:
          "http%3A%2F%2Fabtastylab.com%2F60511af14f5e48764b83d36ddb8ece5a%2F",
        pageTitle: "myScreen",
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a transaction hit
</Button>;

Hit types

Screen

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

<Button
  onClick={() => {
    const mockHit = {
      type: "Screen",
      data: {
        documentLocation: "screenName"
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a screen hit
</Button>;

Attribute	Type	Description
documentLocation	string	Required. Specifies the current name of the screen when the hit is sent.

Page

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

<Button
  onClick={() => {
    const mockHit = {
      type: "Page",
      data: {
        documentLocation:
          "http%3A%2F%2Fabtastylab.com%2F60511af14f5e48764b83d36ddb8ece5a%2F",
        pageTitle: "HomePage"
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a screen hit
</Button>;

Attribute	Type	Description
documentLocation	string	Required. Specifies the current URL of the page when the hit is sent.
pageTitle	string	Optional. Specifies the current name of the page when the hit is sent.

Transaction

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

<Button
  onClick={() => {
    const mockHit = {
      type: "Transaction",
      data: {
        transactionId: "12451342423",
        affiliation: "myAffiliation",
        totalRevenue: 999,
        shippingCost: 888,
        shippingMethod: "DHL",
        currency: "USD",
        taxes: 1234444,
        paymentMethod: "creditCard",
        itemCount: 2,
        couponCode: "myCOUPON",
        documentLocation:
          "http%3A%2F%2Fabtastylab.com%2F60511af14f5e48764b83d36ddb8ece5a%2F",
        pageTitle: "myScreen",
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a transaction hit
</Button>;

Attribute	Type	Description
transactionId	string	Required. The ID of your transaction.
affiliation	string	Required. The name of the KPI that you will have inside your reporting. Learn more
totalRevenue	number	Optional. Specifies the total revenue associated with the transaction. This value should include any shipping and/or tax amounts.
shippingCost	number	Optional. The total shipping cost of your transaction.
shippingMethod	string	Optional. The shipping method for your transaction.
taxes	number	Optional. Specifies the total amount of taxes in your transaction.
currency	string	Optional. Specifies the currency of your transaction. NOTE: This value should be a valid ISO 4217 currency code.
paymentMethod	string	Optional. Specifies the payment method used for your transaction.
itemCount	number	Optional. Specifies the number of items of your transaction.
couponCode	string	Optional. The coupon code associated with the transaction.
documentLocation	string	Optional. Specifies the current URL of the page when the hit is sent.
pageTitle	string	Optional. Specifies the current name of the page when the hit is sent.

Item

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

<Button
  onClick={() => {
    const mockHit = {
      type: "Item",
      data: {
        transactionId: "0987654321",
        name: "testItem",
        price: 999,
        code: "testCode",
        category: "testCategory",
        quantity: 123,
        documentLocation:
          "http%3A%2F%2Fabtastylab.com%2F60511af14f5e48764b83d36ddb8ece5a%2F",
        pageTitle: "testItem",
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a item hit
</Button>;

Attribute	Type	Description
transactionId	string	Required. The ID of your transaction.
name	string	Required. The name of your item.
price	number	Optional. Specifies the price for a single item/unit.
code	string	Optional. Specifies the SKU or item code.
category	string	Optional. Specifies the category that the item belongs to.
quantity	number	Optional. Specifies the number of items purchased.
documentLocation	string	Optional. Specifies the current URL of the page when the hit is sent.
pageTitle	string	Optional. Specifies the current name of the page when the hit is sent.

📘
The Item hit isn't available yet in the Flagship reporting view.

Event

import { useFlagship } from "@flagship.io/react-sdk";

const { hit: fsHit } = useFlagship();

<Button
  onClick={() => {
    const mockHit = {
      type: "Event",
      data: {
        category: "User Engagement",
        action: "signOff",
        label: "Hello world",
        value: 123,
        documentLocation:
          "http%3A%2F%2Fabtastylab.com%2F60511af14f5e48764b83d36ddb8ece5a%2F",
        pageTitle: "testEvent",
      },
    };
    fsHit.send(mockHit);
  }}
>
  Send a event hit
</Button>;

Attribute	Type	Description
category	string	Required. Specifies the category of your event. NOTE: This value must be either `'Action Tracking'` or `'User Engagement'`.
action	string	Required. The name of the KPI you will have inside the reporting.
label	string	Optional. Specifies additional description of your event.
value	number	Optional. Specifies the monetary value associated with an event (e.g. you earn 10 to 100 euros depending on the quality of lead generated). NOTE: this value must be non-negative.
documentLocation	string	Optional. Specifies the current URL of the page when the hit is sent.
pageTitle	string	Optional. Specifies the current name of the page when the hit is sent.

Demos

Following demos illustrate how the SDK is used in practice ☕

Developer Demo

Readme 📖

Live Demo 🕹

Code sandbox Demo

Live Demo 🕹

Ecommerce store Demo

Readme 📖

Live Demo 🕹

Appendix

Release note

Take a look to the Release note.

Contributing

Take a look at the Contributors Guide if you're interested in contributing to the SDK.

License

This Flagship SDK is distributed under the Apache version 2.0 license.