desk2/server/recv.js

import * as des from './deserializer';
import * as send from './send';
import * as math from './math';
import * as storage from './storage';

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

// Session ACKed events up to SN
function recv_ack(d, session) {
    const sn = des.u32(d);

    session.state = SESSION.READY;
    session.sn = sn;

    console.log(`ack ${sn} in`);
}

function handle_event(session, event) {
    switch (event.type) {
        case EVENT.STROKE: {
            event.stroke_id = math.fast_random32();
            storage.put_stroke(event.stroke_id, session.desk_id, event.points, event.width, event.color);
            storage.put_event(event);
            break;
        }

        case EVENT.IMAGE:
        case EVENT.IMAGE_MOVE:
        case EVENT.UNDO: {
            storage.put_event(event);
            break;      
        }

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

async function recv_syn(d, session) {
    const padding = des.u8(d);
    const lsn = des.u32(d);
    const count = des.u32(d);

    console.log(`syn ${lsn} in, total size = ${d.size}`);

    const we_expect = lsn - session.lsn;
    const first = count - we_expect;
    const events = [];

    console.log(`we expect ${we_expect}, count ${count}`);

    for (let i = 0; i < count; ++i) {
        const event = des.event(d);
        if (i >= first) {
            event.desk_id = session.desk_id;
            event.user_id = session.user_id;
            event.stroke_id = null;
            handle_event(session, event);
            events.push(event);
        }
    }

    desks[session.desk_id].sn += we_expect;
    desks[session.desk_id].events.push(...events);
    session.lsn = lsn;

    storage.save_desk_sn(session.desk_id, desks[session.desk_id].sn);
    storage.save_session_lsn(session.id, lsn);

    send.send_ack(session.ws, lsn);
    send.sync_desk(session.desk_id);
}

function recv_fire(d, session) {
    const event = des.event(d);

    for (const sid in sessions) {
        const other = sessions[sid];
        
        if (other.id === session.id) {
            continue;
        }

        if (other.state !== SESSION.READY) {
            continue;
        }

        if (other.desk_id != session.desk_id) {
            continue;
        }

        send.send_fire(other.ws, session.user_id, event);
    }
}

export async function handle_message(ws, d) {
    if (!(ws.data.session_id in sessions)) {
        return;
    }

    const session = sessions[ws.data.session_id];
    const desk_id = session.desk_id;
    const message_type = des.u8(d);

    switch (message_type) {
        case MESSAGE.FIRE: {
            recv_fire(d, session);
            break;
        }

        case MESSAGE.SYN: {
            recv_syn(d, session);
            break;
        }

        case MESSAGE.ACK: {
            recv_ack(d, session);
            break;
        }

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