stremio-web/src/common/useShell.ts

import { useEffect } from 'react';
import EventEmitter from 'eventemitter3';

const SHELL_EVENT_OBJECT = 'transport';
const transport = globalThis?.qt?.webChannelTransport;
const events = new EventEmitter();

enum ShellEventType {
    SIGNAL = 1,
    INVOKE_METHOD = 6,
}

type ShellEvent = {
    id: number;
    type: ShellEventType;
    object: string;
    args: string[];
};

const createId = () => Math.floor(Math.random() * 9999) + 1;

const useShell = () => {
    const on = (name: string, listener: (arg: any) => void) => {
        events.on(name, listener);
    };

    const off = (name: string, listener: (arg: any) => void) => {
        events.off(name, listener);
    };

    const send = (method: string, ...args: (string | number)[]) => {
        try {
            transport?.send(JSON.stringify({
                id: createId(),
                type: ShellEventType.INVOKE_METHOD,
                object: SHELL_EVENT_OBJECT,
                method: 'onEvent',
                args: [method, ...args],
            }));
        } catch (e) {
            console.error('Shell', 'Failed to send event', e);
        }
    };

    useEffect(() => {
        if (!transport) return;

        transport.onmessage = ({ data }) => {
            try {
                const { type, args } = JSON.parse(data) as ShellEvent;

                if (type === ShellEventType.SIGNAL) {
                    const [methodName, methodArg] = args;
                    events.emit(methodName, methodArg);
                }
            } catch (e) {
                console.error('Shell', 'Failed to handle event', e);
            }
        };
    }, []);

    return {
        active: !!transport,
        send,
        on,
        off,
    };
};

export default useShell;