function serializer_create(size) {
    const buffer = new ArrayBuffer(size);
    return {
        'offset': 0,
        'size': size,
        'buffer': buffer,
        'view': new DataView(buffer),
        'strview': new Uint8Array(buffer),
    };
}

function ser_u8(s, value) {
    s.view.setUint8(s.offset, value);
    s.offset += 1;
}

function ser_u16(s, value) {
    s.view.setUint16(s.offset, value, true);
    s.offset += 2;
}

function ser_u32(s, value) {
    s.view.setUint32(s.offset, value, true);
    s.offset += 4;
}

function ser_event(s, event) {
    ser_u8(s, event.type);
    ser_u8(s, 0); // padding for 16bit alignment

    switch (event.type) {
        case EVENT.PREDRAW: {
            ser_u16(s, event.x);
            ser_u16(s, event.y);
            break;
        }

        case EVENT.STROKE: {
            ser_u16(s, event.points.length);
            ser_u16(s, event.width);
            ser_u32(s, event.color);

            if (config.debug_print) console.debug('original', event.points);

            for (const point of event.points) {
                ser_u16(s, point.x);
                ser_u16(s, point.y);
            }

            break;
        }

        case EVENT.IMAGE:
        case EVENT.IMAGE_MOVE: {
            const image_id = parseInt(event.image_id);
            ser_u32(s, image_id);
            ser_u16(s, event.x);
            ser_u16(s, event.y);
            break;
        }

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

        case EVENT.ERASER: {
            ser_u32(s, event.stroke_id);
            break;
        }

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

async function send_ack(sn) {
    const s = serializer_create(1 + 4);

    ser_u8(s, MESSAGE.ACK);
    ser_u32(s, sn);

    if (config.debug_print) console.debug(`ack ${sn} out`);

    try {
        if (ws) await ws.send(s.buffer);
    } catch(e) { 
        ws.close(); 
    }
}

async function sync_queue() {
    if (ws === null) {
        if (config.debug_print) console.debug('socket has closed, stopping SYNs');
        return;
    }

    let size = 1 + 1 + 4 + 4; // opcode + lsn + event count
    let count = storage.lsn - storage.server_lsn;

    if (count === 0) {
        if (config.debug_print) console.debug('server ACKed all events, clearing queue');
        storage.queue.length = 0;
        return;
    }

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

    const s = serializer_create(size);

    ser_u8(s, MESSAGE.SYN);
    ser_u8(s, 0); // padding for 16bit alignment
    ser_u32(s, storage.lsn);
    ser_u32(s, count);

    for (let i = count - 1; i >= 0; --i) {
        const event = storage.queue[storage.queue.length - 1 - i];
        ser_event(s, event);
    }

    if (config.debug_print) console.debug(`syn ${storage.lsn} out`);

    try {
        if (ws) await ws.send(s.buffer);
    } catch(e) { 
        ws.close(); 
    }

    setTimeout(sync_queue, config.sync_timeout);
}

function push_event(event) {
    storage.lsn += 1;

    switch (event.type) {
        case EVENT.STROKE: {
            const points = process_stroke(event.points);
            
            storage.queue.push({ 
                'type': EVENT.STROKE,
                'points': points,
                'width': event.width,
                'color': event.color,
            });

            break;
        }

        case EVENT.RULER: {
            event.type = EVENT.STROKE;
            storage.queue.push(event);
            break;
        }

        case EVENT.ERASER:
        case EVENT.IMAGE:
        case EVENT.IMAGE_MOVE:
        case EVENT.UNDO:
        case EVENT.REDO: {
            storage.queue.push(event);
            break;
        }

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

// Queue an event and initialize repated sends until ACKed
function queue_event(event, skip = false) {
    push_event(event);

    if (skip) {
        return;
    }

    if (storage.timers.queue_sync) {
        clearTimeout(storage.timers.queue_sync);
    }

    sync_queue();
}

// Fire and forget. Doesn't do anything if we are offline
async function fire_event(event) {
    const s = serializer_create(1 + event_size(event));

    ser_u8(s, MESSAGE.FIRE);
    ser_event(s, event);

    try {
        if (ws) await ws.send(s.buffer);
    } catch(e) { 
        ws.close(); 
    }
}