A client can call a transition on a flow instance (using its identifier)

[tomtitherington]

Background & Context*

Once a client has a valid Websocket connection to the server, they should be able to call a transition defined on a FlowSchema / TransitionSchema using the TransitionSchema.identifier.

Goal*

• A client should be able to call the transition.
• If the transition is valid then they will get an OK response.
• If the transition is not valid they will get a FAIL response and appropriate error(s).
• If the transition condition evaluates to False and cannot be executed then they will get a FAIL response with the appropriate error(s).

Implementation Details*

Requests and responses should adhere to the following format.

// Example request
{
  "action": "transition",
  "request_id": Date.now(),
  "data": {
    "flow_instance_id": "string",
    "step_schema_identifier": "string",
    "transition_schema_identifier": "string"

  }
}
// Example response
{
  "request_id": 1519211809934,
  "errors": [],
  "status": 200,
  "data" : {
    "result": "string (success, failure)"
    "message": "null | string (if result is failure)"
    "flow_instance_id": "string",
    "step_schema_id": "string",
    "transition_schema_identifier": "string",
  }
}

Acceptance Criteria*

Test cases that

• Assert that given a valid TransitionSchema.identifer and FlowInstance.id the server will respond with a 200 / status OK.
• Assert that given a valid TransitionSchema.identifer and FlowInstance.id the server will transition the flow and the current active flow should become the previously active flow.
• Assert that given an invalid TransitionSchema.identifer or FlowInstance.id the server will respond with an error / status FAIL.

Dependencies

Blockers:

• Setup flow engine #22
• Setup Websocket consumers #62

*required field.