desk2/client/index.js

let ws = null;
let ls = window.localStorage;

document.addEventListener('DOMContentLoaded', main);

const EVENT = Object.freeze({
    PREDRAW: 10,
    STROKE: 20,
    UNDO: 30,
    REDO: 31,
});
const MESSAGE = Object.freeze({
    INIT: 100,
    SYN: 101,
    ACK: 102,
    FULL: 103,
    FIRE: 104,
    JOIN: 105,
});

const config = {
    ws_url: 'wss://desk.local/ws/', 
    sync_timeout: 1000,
    ws_reconnect_timeout: 2000,
};

const storage = {
    'state': {
        'drawing': false,
        'moving': false,
    },

    'predraw': {},
    'timers': {},
    'me': {},

    'sn': 0, // what WE think SERVER SN is (we tell this to the server, it uses to decide how much stuff to SYN to us)
    'server_lsn': 0, // what SERVER said LSN is (used to decide how much stuff to SYN)
    'lsn': 0, // what actual LSN is (can't just use length of local queue because it gets cleared)
    'queue': [], // to server
    'events': [], // from server
    'current_stroke': [],

    'desk_id': 123,

    'canvas': {
        'width': 2000,
        'height': 2000,
        'offset_x': 0,
        'offset_y': 0,
    },

    'cursor': {
        'width': 8,
        'x': 0,
        'y': 0,
    }
};
const elements = {
    'cursor': null,
    'canvas0': null,
    'canvas1': null,
};

function event_size(event) {
    let size = 1 + 1; // type + padding

    switch (event.type) {
        case EVENT.PREDRAW: {
            size += 2 * 2;
            break;
        }

        case EVENT.STROKE: {
            size += 2 + event.points.length * 2 * 2; // u16 (count) + count * (u16, u16) points
            break;
        }

        case EVENT.UNDO:
        case EVENT.REDO: {
            break;
        }

        default: {
            console.error('fuck');
            process.exit(1);
        }
    }

    return size;
}

function predraw_event(x, y) {
    return {
        'type': EVENT.PREDRAW,
        'x': x,
        'y': y
    };
}

function stroke_event() {
    return { 
        'type': EVENT.STROKE,
        'points': storage.current_stroke,
    };
}

function undo_event() {
    return { 'type': EVENT.UNDO };
}

function redo_event() {
    return { 'type': EVENT.REDO };
}

function main() {
    const url = new URL(window.location.href);
    const parts = url.pathname.split('/');
    
    storage.desk_id = parts.length > 0 ? parts[parts.length - 1] : 0;

    ws_connect();

    elements.canvas0 = document.getElementById('canvas0');
    elements.canvas1 = document.getElementById('canvas1');
    elements.cursor = document.getElementById('cursor');
    elements.cursor.style.width = storage.cursor.width + 'px';
    elements.cursor.style.height = storage.cursor.width + 'px';

    storage.canvas.rect = elements.canvas0.getBoundingClientRect();

    storage.ctx0 = elements.canvas0.getContext('2d');
    storage.ctx1 = elements.canvas1.getContext('2d');
    storage.ctx1.canvas.width = storage.ctx0.canvas.width = storage.canvas.width;
    storage.ctx1.canvas.height = storage.ctx0.canvas.height = storage.canvas.height;

    storage.ctx1.lineJoin = storage.ctx1.lineCap = storage.ctx0.lineJoin = storage.ctx0.lineCap = 'round';
    storage.ctx1.lineWidth = storage.ctx0.lineWidth = storage.cursor.width;

    window.addEventListener('pointerdown', on_down)
    window.addEventListener('pointermove', on_move)
    window.addEventListener('pointerup', on_up);
    window.addEventListener('pointercancel', on_up);
    window.addEventListener('touchstart', (e) => e.preventDefault());
    window.addEventListener('keydown', on_keydown);
    window.addEventListener('keyup', on_keyup);
    // window.addEventListener('pointerleave', on_leave);
}