otis

another operational transformation library for JSON values.

this is PRE-RELEASE SOFTWARE! USE AT YOUR OWN RISK, ABANDON ALL HOPE YE WHO ENTER HERE, etc and so on.

this library provides:

the type Value and its constructor represent. a Value can only be or contain plain, simple JSON values, eg strings and numbers, not Date objects or functions.

you can use these together to essentially guarantee that you are working with plain values. it may be overkill, it's probably overkill.
the type Operation and its concrete implementations (listed below).
a robot state machine (Editor) which can be used to power an interactive, collaborative editing session of some kind. you can see an example of what the editor is currently capable of below in the synopsis.

Operations

The currently exported Operations are

NoOp: more of an internal utility than anything;
Splice: generalization of insertion and deletion, generalized for both strings and arrays;
Insert: convenient shorthand for a splice which deletes nothing;
Delete: convenient shorthand for a splice which inserts nothing;
Move: moves an array item or string character from one position to another;
ArrayApply: applies an operation to a given array index;
Set: sets an array item, object value, or scalar value;
Map: maps an operation over an array;
List: combines a sequence of multiple independent operations into one;
Put: puts a value at a given index on an object;
Remove: removes a given key on an object;
Rename: renames a given object key;
ObjectApply: applies an operation to an object.

synopsis

import {
  serialize,
  ObjectApply,
  ArrayApply,
  Set,
  Rename,
  Editor,
  create_editor
} from "otis";

const editor: Editor = create_editor("doc-1", {
  a: 3,
  c: ["cool",false]
}, () => {
  console.log(`applied edit: ${JSON.stringify(serialize(editor.context._history[0]))}`);
});

editor.send({
  type: "edit",
  operation: new Rename("a", "A"),
  base_revision: 0,
  sender_id: "sender-1"
});

editor.send({
  type: "edit",
  operation: new Rename("c", "B"),
  base_revision: 1,
  sender_id: "sender-1"
});

editor.send({
  type: "edit",
  operation: new ObjectApply("c", new ArrayApply(1, new Set(false, true))),
  base_revision: 1,
  sender_id: "sender-2"
});

console.log("result", JSON.stringify(editor.context, null, 2));

The output of this program is

> otis@0.1.2 dev
> ts-node src/index.ts

applied edit: {"tag":"Rename","args":{"old_key":"a","new_key":"A"}}
applied edit: {"tag":"Rename","args":{"old_key":"c","new_key":"B"}}
applied edit: {"tag":"ObjectApply","args":{"key":"B","op":{"tag":"ArrayApply","args":{"pos":1,"op":{"tag":"Set","args":{"old_value":false,"new_value":true}}}}}}
result {
  "_id": "doc-1",
  "_body": {
    "A": 3,
    "B": [
      "cool",
      true
    ]
  },
  "_revision": 3,
  "_history": [
    {
      "key": "B",
      "op": {
        "pos": 1,
        "op": {
          "old_value": false,
          "new_value": true
        }
      }
    },
    {
      "old_key": "c",
      "new_key": "B"
    },
    {
      "old_key": "a",
      "new_key": "A"
    }
  ]
}

gatlin/otis

otis

Operations

synopsis