Leaps API

This document outlines the potential Leaps API request/responses in JSON format. Transport between the client and server is asynchronous, and currently implemented with websockets.

To begin a connection the client must connect to the endpoint: ws://<server>:<port>/leaps/ws?username=<username>, note that the username is added to the URL in the query params.

Once the websockets connection is established the server/client communications are confined to the following JSON format:

{
	"type": "<string>",
	"body": {
		"error": {
			"type": "<string>",
			"message": "<string>"
		},
		"client": {
			"username": "<string>",
			"session_id": "<string>"
		},
		"transform": {
			"insert": "<string>",
			"position": "<int>",
			"num_delete": "<int>"
		},
		"correction": {
			"version": "<int>"
		},
		"metadata": {
			"type": "<string>",
			"body": "<object>"
		},
		"document": {
			"id": "<string>",
			"content": "<string>",
			"version": "<int>"
		}
	}
}

Request/Response Types

Client Request Types

Clients can send requests of the following types: subscribe, unsubscribe, transform, metadata, global_metadata, ping.

Which perform the following actions:

Subscribe

In order to start editing a document it must be subscribed to. The client makes a subscribe type request which details the document that it intends to edit.

The request looks as follows:

{
	"type": "subscribe",
	"body": {
		"document": {
			"id": "<string, id of document>"
		}
	}
}

The service then will respond with either a subscribe or an error event.

Unsubscribe

When a document subscription is active and the client no longer has an interest in it they can use the unsubscribe request, which looks as follows:

{
	"type": "unsubscribe",
	"body": {
		"document": {
			"id": "<string, id of document>"
		}
	}
}

The service then will respond with either an unsubscribe or an error event.

Transform

When a subscribed document is edited by the client it must submit a transform request, which looks as follows:

{
	"type": "transform",
	"body": {
		"document": {
			"id": "<string, id of target document>"
		},
		"transform": {
			"insert": "<string, text to insert>",
			"position": "<int, position of change>",
			"num_delete": "<int, number of characters to delete>"
		}
	}
}

The service will respond with either a correction or an error event.

Metadata

Sometimes clients need to send their own custom data to other clients. Leaps will route any metadata type of message to other clients subscribed to the same document, which looks as follows:

{
	"type": "metadata",
	"body": {
		"document": {
			"id": "<string, id of target document>"
		},
		"metadata": {
			"type": "<string, type of metadata>",
			"body": "<object, the metadata itself>"
		}
	}
}

The service will not respond to a metadata request unless an error occurs.

Global Metadata

Clients may also send metadata to all users connected to the leaps service, regardless of subscription. This is done with the global_metadata event, which is similar in all other ways to the metadata event, and looks as follows:

{
	"type": "global_metadata",
	"body": {
		"metadata": {
			"type": "<string, type of metadata>",
			"body": "<object, the metadata itself>"
		}
	}
}

The service will not respond to a global_metadata request unless an error occurs.

Ping

Send a ping event to get back a pong event, there is no body to the request so it looks like this:

{
	"type": "ping",
	"body": {}
}

Server Response Types

Servers will send responses of the following types: subscribe, unsubscribe, correction, transforms, metadata, global_metadata, pong.

Which perform the following actions:

Subscribe

When a client makes a subscribe request, and the request is successful, the server will also respond with a subscribe typed response.

The response looks as follows:

{
	"type": "subscribe",
	"body": {
		"document": {
			"id": "<string, id of document>",
			"content": "<string, the current content of the document>",
			"version": "<int, the current version of the document>"
		}
	}
}

Unsubscribe

When a client makes an unsubscribe request, and the request is successful, the server will also respond with an unsubscribe typed response.

The response looks as follows:

{
	"type": "unsubscribe",
	"body": {
		"document": {
			"id": "<string, id of document>"
		}
	}
}

Correction

When a client submits a transform it is speculative in that the version of the transform is only what the client expects it to be. The server then processes the transform, corrects it, and then responds with a correction typed response of the following format:

{
	"type": "correction",
	"body": {
		"document": {
			"id": "<string, id of document>"
		},
		"correction": {
			"version": "<int, the actual version of the last submitted transform>"
		}
	}
}

Transforms

A document transform submitted by a client will be broadcast to all other subscribed clients. Those clients receive a transforms typed message, as this message may potentially contain multiple transforms.

The response looks as follows:

{
	"type": "transforms",
	"body": {
		"document": {
			"id": "<string, id of document>"
		},
		"transforms": [
			{
				"insert": "<string, text to insert>",
				"position": "<int, position of change>",
				"num_delete": "<int, number of characters to delete>"
			}
		]
	}
}

The service will respond with either a correction or an error event.

Metadata

Metadata submitted from subscribed clients are broadcast to all other subscribed clients in the same format with additional client identifying information:

{
	"type": "metadata",
	"body": {
		"client": {
			"username": "<string, username of the source client>",
			"session_id": "<string, unique uuid of the source client>"
		},
		"document": {
			"id": "<string, id of document>"
		},
		"metadata": {
			"type": "<string, type of metadata>",
			"body": "<object, the metadata itself>"
		}
	}
}

Global Metadata

Global metadata submitted from clients are broadcast to all other connected clients in the same format with additional client identifying information:

{
	"type": "global_metadata",
	"body": {
		"client": {
			"username": "<string, username of the source client>",
			"session_id": "<string, unique uuid of the source client>"
		},
		"metadata": {
			"type": "<string, type of metadata>",
			"body": "<object, the metadata itself>"
		}
	}
}

There are a number of global_metadata events that the server sends automatically during a connection, such as user_info. To read about these events, as well as any established client events, you can read the metadata spec here.

Pong

Sent back after receiving a ping request.

{
	"type": "pong",
	"body": {}
}