esdeka v0.1.18

Esdeka

Communicate between <iframe> and host

Table of Contents

• Mechanism
  • Creating a connection
• Functions
  • call
  • answer
  • disconnect
  • subscribe
  • dispatch
  • broadcast
• React hooks
  • useHost
  • useGuest
• Bundle size
• Full React example (using Zustand)

Mechanism

Esdeka uses window.postMessage to communicate to iframes. It offers several helpers to make communication as easy as possible.

We stream data down to the iframe. If the iframe wants to communicate back it dispatches an action with an optional payload. We can then decide how to act on the transmitted data.

Creating a connection

To create a connection we need to call a client and wait for an answer.

Setting up a Host.

import { call } from "esdeka";

const iframe = document.querySelector("iframe");

call(iframe.contentWindow, "my-channel", { some: "Data" });

Setting up a Guest.

import { answer, subscribe } from "esdeka";

subscribe("my-channel", event => {
  if (event.data.action.type === "call") {
    answer(event.source, "my-channel");
  }
});

Once a connection exists, we can broadcast information from the host to the guest.

Host

import { broadcast, call, subscribe } from "esdeka";

const iframe = document.querySelector("iframe");

call(iframe.contentWindow, "my-channel", { some: "Data" });

subscribe("my-channel", event => {
  if (event.data.action.type === "answer") {
    broadcast(event.source, "my-channel", {
      question: "How are you?",
    });
  }
});

The guest subscribes to all messages and act accordingly.

Guest

import { answer, subscribe } from "esdeka";

const questions = [];

subscribe("my-channel", event => {
  const { type, payload } = event.data.action;
  switch (type) {
    case "broadcast":
      if (payload?.question) {
        questions.push(payload.question);
      }
      break;
    case "call":
      answer(event.source, "my-channel");
      break;
    default:
      console.error("Not implemented");
      break;
  }
});

Functions

call

Sends a connection request from the host to a guest. The payload can be anything that you want to send through a channel.

call(window, "my-channel", {
  message: "Hello",
});

answer

Answer to a host to confirm the connection.

answer(window, "my-channel");

disconnect

Tell the host that the guest disconnected.

disconnect(window, "my-channel");

subscribe

Listen to all messages in a channel.

subscribe("my-channel", event => {
  console.log(event);
});

dispatch

Send an action to Esdeka. The host will be informed and can act un the request.

Without payload

dispatch(window, "my-channel", {
  type: "increment",
});

With payload

dispatch(window, "my-channel", {
  type: "greet",
  payload: {
    message: "Hello",
  },
});

broadcast

Send data from the host window to the guest. The payload can be anything that you want to send through a channel.

broadcast(window, "my-channel", {
  message: "Hello",
});

React hooks

useHost

Curried host functions that don't need the window and channel.

const { broadcast, call, subscribe } = useHost(ref, "my-channel");

call({
  message: "Hello",
});

broadcast({
  message: "Hello",
});

subscribe(event => {
  console.log(event);
});

useGuest

Curried guest functions that don't need the window and channel.

const { answer, disconnect, dispatch, subscribe } = useGuest(ref, "my-channel");

answer();

disconnect();

subscribe(event => {
  console.log(event);
});

dispatch({
  type: "greet",
  payload: {
    message: "Hello",
  },
});

Bundle size

All bundles are smaller than 1KB

 PASS  ./dist/index.js: 568B < maxSize 1KB (gzip)

 PASS  ./dist/index.mjs: 526B < maxSize 1KB (gzip)

 PASS  ./dist/react.js: 752B < maxSize 1KB (gzip)

 PASS  ./dist/react.mjs: 729B < maxSize 1KB (gzip)

Full React example (using Zustand)

Host

http://localhost:3000/

import { serialize, useHost } from "esdeka/react";
import { DetailedHTMLProps, IframeHTMLAttributes, useEffect, useRef, useState } from "react";
import create from "zustand";

export interface StoreModel {
  counter: number;
  increment(): void;
  decrement(): void;
}

export const useStore = create<StoreModel>(set => ({
  counter: 0,
  increment() {
    set(state => ({ counter: state.counter + 1 }));
  },
  decrement() {
    set(state => ({ counter: state.counter - 1 }));
  },
}));

export interface EsdekaHostProps
  extends DetailedHTMLProps<IframeHTMLAttributes<HTMLIFrameElement>, HTMLIFrameElement> {
  channel: string;
  maxTries?: number;
  interval?: number;
}

export function EsdekaHost({ channel, maxTries = 30, interval = 30, ...props }: EsdekaHostProps) {
  const ref = useRef<HTMLIFrameElement>(null);
  const connection = useRef(false);
  const [tries, setTries] = useState(maxTries);

  const { broadcast, call, subscribe } = useHost(ref, channel);

  // Send a connection request
  useEffect(() => {
    if (connection.current || tries <= 0) {
      return () => {
        /* Consistency */
      };
    }

    call(serialize(useStore.getState()));
    const timeout = setTimeout(() => {
      call(serialize(useStore.getState()));
      setTries(tries - 1);
    }, interval);

    return () => {
      clearTimeout(timeout);
    };
  }, [call, tries, interval]);

  useEffect(() => {
    if (!connection.current) {
      const unsubscribe = subscribe(event => {
        const store = useStore.getState();
        const { action } = event.data;
        switch (action.type) {
          case "answer":
            connection.current = true;
            break;
          default:
            if (typeof store[action.type] === "function") {
              store[action.type](action.payload.store);
            }
            break;
        }
      });
      return () => {
        unsubscribe();
      };
    }
    return () => {
      /* Consistency */
    };
  }, [subscribe]);

  // Broadcast store to guest
  useEffect(() => {
    if (connection.current) {
      const unsubscribe = useStore.subscribe(newState => {
        broadcast(serialize(newState));
      });
      return () => {
        unsubscribe();
      };
    }
    return () => {
      /* Consistency */
    };
  }, [broadcast]);

  return <iframe ref={ref} {...props} />;
}

export default function App() {
  const increment = useStore(state => state.increment);
  const decrement = useStore(state => state.decrement);
  const counter = useStore(state => state.counter);
  return (
    <div>
      <button onClick={increment}>Up</button>
      <span>{counter}</span>
      <button onClick={decrement}>Down</button>
      <EsdekaHost channel="esdeka-test" src="http://localhost:3001" />
    </div>
  );
}

Guest

http://localhost:3001

import { useGuest } from "esdeka/react";
import { useEffect, useState } from "react";
import create from "zustand";

export interface StoreModel {
  [key: string]: any;
  // eslint-disable-next-line no-unused-vars
  set(state: Omit<StoreModel, "set">): void;
}

export const useStore = create<StoreModel>(set => ({
  set(state) {
    set(state);
  },
}));

export function EsdekaGuest({ channel }: { channel: string }) {
  const counter = useStore(state => state.counter);
  const host = useRef<Window | null>(null);
  const { answer, dispatch, subscribe } = useGuest();

  useEffect(() => {
    const unsubscribe = subscribe<Except<StoreModel, "set">>(event => {
      const { action } = event.data;
      switch (action.type) {
        case "call":
          host.current = event.source as Window;
          answer();
          break;
        case "broadcast":
          useStore.getState().set(action.payload);
          break;
        default:
          break;
      }
    });
    return () => {
      unsubscribe();
    };
  }, [answer, subscribe]);

  return (
    <div>
      <h1>Current Count: {counter}</h1>
      <button
        onClick={() => {
          dispatch({ type: "decrement" });
        }}
      >
        Down
      </button>
      <button
        onClick={() => {
          dispatch({ type: "increment" });
        }}
      >
        Up
      </button>
    </div>
  );
}

export default function Page() {
  return <EsdekaGuest channel="esdeka-test" />;
}