# Cloud Based Flowmanager Flow

This page describes the flow when GPII is run in cloud based flowmanager mode. This mainly involves two files:

* `CloudBasedFlowManager.js` - This will be referred to as `Cloud Based FlowManager` in the below
* `MatchMaking.js` - referred to in the below as `FlowManagerRequests`.

## Overview and APIs

The Cloud Based FlowManager can be considered as a standalone, cloud-only configuration of the GPII. This is relevant
for applications that are built to support this, and running on a system without the core GPII installed. So for
example, a simple javaphone that has a built-in support for GPII, but is not running the core architecture. This can
send a GPII key and platform information to the Cloud Based FlowManager, and get instructions back on how it should be
set up.

The endpoint for this service is at `:gpiiKey/settings/:device` (where `:gpiiKey` is the GPII key to log in and
`:device` is information about the current platform.)

## Detailed walkthrough of flow:

The process of retrieving application lifecycle instructions in the Cloud Based FlowManager mode is as follows:

1. GET request is sent to the `:gpiiKey/settings/:device` URL where `:gpiiKey` is the GPII key to log in and `:device`
   is a device reporter payload, like: `{"OS":{"id":"web"},"solutions":[{"id":"org.chrome.cloud4chrome"}]}`. It is
   handled by the `onSettings` (Cloud Based FlowManager) function which ensures the device payload is valid and fires
   two events: `onGpiiKey` and `onDeviceContext`
2. `onGpiiKey` event has two listeners:
   * `getPreferences` (FlowManagerRequests) which fetches the preferences and fires the `onPreferences` event when the
    preferences are fetched.
   * `setGpiiKey` (FlowManagerRequests) which sets the gpiiKey property in the handler
3. `onDeviceContext` event has one listener:
   * `getSolutions` (FlowManagerRequests) which fetches the solutions registry and filters it based on the device
     reporter info.  The `onSolutions` event is fired with the result. The `onReadyToMatch` event is listening to the
     three events described above: `onDeviceContext`, `onPreferences` and `onSolutions`. When these three events have
     been fired, the `onReadyToMatch` event will be triggered.
4. This event signal that all the resources has been fetched and the matchmaking related portion of the workflow starts.
   This is done via the `processMatch` pseudo event, which is listening to the `onReadyToMatch` event and triggered from
   it. The `processMatch` event kickes off a set of functions fired sequentially as dictated by the
   `flowManager.processMatch.priorities`. As with everything else in this flow, the sequence and ordering of the steps
   in the matchmaking process can be modified by the config/setup being used, and this document wont dive into the
   details of this flow except for some general observatiosn:
   * Generally some prioritized steps: `preProcess`, `matchMakerDispatcher`, `updateActivePrefsSetName` and `transform`
   will be run (in that order).
   * The end result of this process is a description of the configuration to be applied to system, described per
    application. The event `onMatchDone` signals that we have the lifecycle instructions ready. For more details on the
    MatchMaker frameworks internal workings, see: [MatchMaker Framework Documentation](MatchMakerFramework.md)
5. `onMatchDone` is being listened to by the `matchToSettings` function (Cloud Based FlowManager) which takes and puts
   the lifecycle instructions in the response to the requesting application.