desk2/server/send.js

import * as math from './math';
import * as ser from './serializer';
import * as storage from './storage';
import * as config from './config';

import { MESSAGE, SESSION, EVENT } from './enums';
import { sessions, desks } from './storage';

function event_size(event) {
    let size = 1 + 4; // type + user_id

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

        case EVENT.STROKE: {
            size += 2; // point count
            size += event.points.byteLength;
            break;
        }

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

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

    return size;
}

function create_session(ws, desk_id) {
    const user = {
        id: math.crypto_random32(),
        login: 'unnamed',
    };

    const session = {
        id: math.crypto_random32(),
        user_id: user.id,
        desk_id: desk_id,
        state: SESSION.OPENED,
        sn: 0,
        lsn: 0,
        ws: ws,
    };

    storage.create_user(user);
    storage.create_session(session);

    sessions[session.id] = session;

    return session;
}

export async function send_init(ws) {
    const session_id = ws.data.session_id;
    const desk_id = ws.data.desk_id;
    const desk = desks[desk_id];

    let opcode = MESSAGE.INIT;
    let size = 1 + 4 + 4 + 4 + 4; // opcode + user_id + lsn + event count + stroke count
    let session = null;

    if (session_id in sessions && sessions[session_id].desk_id == desk_id) {
        session = sessions[session_id];
    } else {
        size += 4; // session id
        opcode = MESSAGE.JOIN;
        session = create_session(ws, desk_id);
        ws.data.session_id = session.id;
    }

    session.desk_id = desk_id;
    session.ws = ws;
    session.sn = 0; // Always re-send everything on reconnect
    session.state = SESSION.OPENED;

    console.log(`session ${session.id} opened`);

    for (const event of desk.events) {
        size += event_size(event);
    }

    const s = ser.create(size);

    ser.u8(s, opcode);
    ser.u32(s, session.user_id);
    ser.u32(s, session.lsn);

    if (opcode === MESSAGE.JOIN) {
        ser.u32(s, session.id);
    }

    ser.u32(s, desk.events.length);

    for (const event of desk.events) {
        ser.event(s, event);
    }

    await ws.send(s.buffer);
}

export function send_ack(ws, lsn) {
    const size = 1 + 4; // opcode + lsn
    const s = ser.create(size);

    ser.u8(s, MESSAGE.ACK);
    ser.u32(s, lsn);

    console.log(`ack ${lsn} out`);

    ws.send(s.buffer);
}

export function send_fire(ws, user_id, event) {
    const s = ser.create(1 + 4 + event_size(event));

    ser.u8(s, MESSAGE.FIRE);
    ser.u32(s, user_id);
    ser.event(s, event);

    ws.send(s.buffer);
}

async function sync_session(session_id) {
    if (!(session_id in sessions)) {
        return;
    }

    const session = sessions[session_id];
    const desk = desks[session.desk_id];

    if (session.state !== SESSION.READY) {
        return;
    }

    let size = 1  + 4 + 4; // opcode + sn + event count
    let count = desk.sn -  session.sn;

    if (count === 0) {
        console.log('client ACKed all events');
        return;
    }

    for (let i = count - 1; i >= 0; --i) {
        const event = desk.events[desk.events.length - 1 - i];
        size += event_size(event);
    }

    const s = ser.create(size);

    ser.u8(s, MESSAGE.SYN);
    ser.u32(s, desk.sn);
    ser.u32(s, count);

    for (let i = count - 1; i >= 0; --i) {
        const event = desk.events[desk.events.length - 1 - i];
        ser.event(s, event);
    }

    console.debug(`syn ${desk.sn} out`);

    await session.ws.send(s.buffer);

    session.sync_timer = setTimeout(() => sync_session(session_id), config.SYNC_TIMEOUT);
}

export function sync_desk(desk_id) {
    for (const sid in sessions) {
        const session = sessions[sid];
        if (session.state === SESSION.READY && session.desk_id == desk_id) { // NOT ===, because might be string or int IDK
            if (session.sync_timer) {
                clearTimeout(session.sync_timer);
            }
            sync_session(sid);
        }
    }
}