reka.js

Reka is a state management system for building no-code editors.

Why?

Much of the complexity surrounding building no-code editors comes from architecting the state management system to power such editors (ie: how should the end user designs be stored and edited in a page editor?)

Reka solves this by providing an AST-powered state system that enables end-users to create UI components that are nearly as complex as ones that developers could write in code; along with an interpreter to efficiently compute an output that could be rendered on the browser.

It's primarily built to serve as the new state management system to power Craft.js and its page builders.

Features

AST-based State ⚡

At the core of Reka is the State data structure which is an Abstract Syntax Tree (AST). This enables end-users to build complex UI components with features that developers are familiar with from UI frameworks such as React:

[
  {
    type: 'RekaComponent',
    name: 'Counter',
    props: [
      {
        type: 'ComponentProp',
        name: 'initalValue',
        init: { type: 'Literal', value: 0 },
      },
    ],
    state: [
      {
        type: 'Val',
        name: 'counter',
        init: { type: 'Identifier', name: 'initialValue' },
      },
    ],
    template: {
      type: 'TagTemplate',
      tag: 'p',
      props: {},
      children: [
        {
          type: 'TagTemplate',
          tag: 'text',
          props: { value: { type: 'Literal', value: 'My counter: ' } },
        },
        {
          type: 'TagTemplate',
          tag: 'text',
          props: { value: { type: 'Identifier', value: 'counter' } },
        },
      ],
    },
  },
  {
    type: 'RekaComponent',
    name: 'App',
    state: [],
    template: {
      type: 'TagTemplate',
      tag: 'div',
      props: {},
      children: [{ type: 'TagTemplate', component: 'Counter', props: {} }],
    },
  },
];

// which is the equivalent of the following React code:
const Counter = ({ initialValue = 0 }) => {
  const [counter, setCounter] = useState(initialValue);

  return <p>My Counter: {counter}</p>;
};

const App = () => {
  return (
    <div>
      <Counter initalValue={10} />
    </div>
  );
};

This means you could build page editors where your end-users are able to design entire UI components with stateful values and templating capabilities (ie: conditionally rendering elements, expressions as props, rendering elements from a list etc)

Portable 🚗

Reka computes a Component instance from its State by generating a View tree:

// Compute a View for the Counter component
const frame = await reka.createFrame({
  id: 'my-basic-counter-instance',
  component: {
    name: 'Counter',
    props: { initialValue: t.literal({ value: 10 }) }
  }
});

console.log(frame.view);
// console:
{
    type: "RekaComponentView",
    component: { type: "RekaComponent", component: "Counter" },
    root: {
        type: "TagView",
        tag: "p",
        props: {},
        children: [
            { type: "TagView", tag: "text", props: { value: "My counter: " }},
            { type: "TagView", tag: "text", props: { value: 10 }}
        ]
    }
}

Whenever there's a change made to the State (eg: adding a new child to a parent template), Reka efficiently recomputes the updated View.

The View tree is a simple serializable JSON structure. So regardless of what UI framework you're working with to build your page builder - whether it's React, Vue or Svelte; building a renderer for Reka simply means taking this JSON structure and rendering it in your preferred UI framework.

Extensible State 🔨

Of course, page builders oftentimes may require additional data to be stored as part of the State. For example, let's say you want your end-users to be able to leave a comment on a template element; you can store these comments directly as part of the State:

import { createExtension } from '@rekajs/core';

type CommentState = {
  comments: Array<{
    templateId: string; // Id of the Template element associated with the comment
    content: string;
  }>;
};

const CommentExtension = createExtension<CommentState>({
  key: 'comments',
  state: {
    // initial state
    comments: [],
  },
  init: (extension) => {
    // do whatever your extension may have to do here
    // ie: send some data to the backend or listen to some changes made in State
  },
});

// Usage
reka.change(() => {
  reka.getExtension(CommentExtension).state.comments.push({
    templateId: '...',
    content: 'This button tag should be larger!!',
  });
});

External Functionalities 🔥

You may also want to expose additional functionalities for the end-users of your page builder to use. For example, let's say you want your end-users to have the ability to output the current date time:

// 1) Expose function to return current time
const reka = Reka.create({
  externals: {
    functions: [
      t.externalFunc({
        name: 'getDateTime',
        func: () => {
          return Date.now();
        },
      }),
    ],
  },
});

// 2) External function is now accessible throughout the State:
reka.load(
  t.state({
    program: t.program({
      components: [
        t.rekaComponent({
          name: 'App',
          states: [],
          props: [],
          template: t.tagTemplate({
            tag: 'text',
            props: {
              value: t.binaryExpression({
                left: t.literal({ value: 'Current date time is: ' }),
                operator: '+',
                right: t.callExpression({
                  identifier: {
                    name: 'getDateTime', // <-- access exposed function to return current time
                    external: true,
                  },
                  params: {},
                }),
              }),
            },
          }),
        }),
      ],
    }),
  })
);

Realtime Collaboration 🎉

Oh, you need multiplayer in your page editor too? No problem, Reka provides an external package that allows real-time collaboration via a fully-featured CRDT backed by Yjs

import { Reka } from '@rekajs/core';
import * as t from '@rekajs/types';
import { createCollabExtension } from '@rekajs/collaboration';

import * as Y from 'yjs';
import { WebrtcProvider } from 'y-webrtc';

const doc = new Y.Doc();
const type = doc.getMap('my-collaborative-editor');

const reka = Reka.create({
  extensions: [createCollabExtension(type)],
});

reka.load(t.unflatten(type.getMap('document')));

new WebrtcProvider('collab-room', doc);

Acknowledgments 🙌

Reka is inspired by Plasmic, Builder.io and Mitosis