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

        'need_gpu_allocate': true, // need to call glBufferData to create a GPU buffer of size serializer.size
        'gpu_upload_from': 0,      // need to call glBufferSubData for bytes in [serializer.gpu_upload_from, serializer.offset)
    };
}

function ser_ensure(s, size) {
    if (s.size < size) {
        const new_s = serializer_create(Math.ceil(size * 2));

        new_s.strview.set(s.strview);
        new_s.offset = s.offset;

        return new_s;
    }

    return s;
}

function ser_ensure_by(s, by) {
    if (s.offset + by > s.size) {
        const new_s = serializer_create(Math.ceil((s.size + by) * 2));

        new_s.strview.set(s.strview);
        new_s.offset = s.offset;

        return new_s;
    }

    return s;
}

function ser_clear(s) {
    s.offset = 0;
    s.gpu_upload_from = 0;
}

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_f32(s, value) {
    s.view.setFloat32(s.offset, value, true);
    s.offset += 4;
}

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

function ser_s32(s, value) {
    s.view.setInt32(s.offset, value, true);
    s.offset += 4;
}

function ser_align(s, to) {
    // TODO: non-stupid version of this
    while (s.offset % to != 0) {
        s.offset++;
    }
}

function ser_event(s, event) {
    ser_u32(s, event.type);
    
    switch (event.type) {
        case EVENT.PREDRAW: {
            ser_f32(s, event.x);
            ser_f32(s, event.y);
            break;
        }

        case EVENT.CLEAR: {
            break;            
        }

        case EVENT.MOVE_CURSOR: {
            ser_f32(s, event.x);
            ser_f32(s, event.y);
            break;
        }

        case EVENT.MOVE_CANVAS: {
            ser_u32(s, event.offset_x);
            ser_u32(s, event.offset_y);
            ser_s32(s, event.zoom_level);
            break;
        }

        case EVENT.ZOOM_CANVAS: {
            ser_s32(s, event.zoom_level);
            ser_f32(s, event.zoom_cx);
            ser_f32(s, event.zoom_cy);
            break;
        }

        case EVENT.SET_COLOR: {
            ser_u32(s, event.color);
            break;
        }

        case EVENT.SET_WIDTH: {
            ser_u16(s, event.width);
            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_f32(s, point.x);
                ser_f32(s, point.y);
            }

            for (const point of event.points) {
                ser_u8(s, point.pressure);
            }

            ser_align(s, 4);

            break;
        }

        case EVENT.IMAGE:
        case EVENT.IMAGE_MOVE: {
            const image_id = parseInt(event.image_id);
            ser_u32(s, image_id);
            ser_f32(s, event.x);
            ser_f32(s, event.y);
            ser_u32(s, event.width);
            ser_u32(s, event.height);
            break;
        }

        case EVENT.IMAGE_SCALE: {
            const image_id = parseInt(event.image_id);
            ser_u32(s, image_id);
            ser_u32(s, event.corner);   // which corner was moved
            ser_f32(s, event.x);  // where corner was moved to (canvas coordinates)
            ser_f32(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(4 + 4);

    ser_u32(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 send_follow(player_id) {
    const s = serializer_create(4 + 4);

    player_id = player_id === null ? -1 : player_id;

    ser_u32(s, MESSAGE.FOLLOW);
    ser_u32(s, player_id);

    if (config.debug_print) console.debug(`follow ${player_id} out`);
    
    try {
        if (ws) await ws.send(s.buffer);
    } catch (e) {
        ws.close();
    }
}

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

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

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

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

    const s = serializer_create(size);

    ser_u32(s, MESSAGE.SYN);
    ser_u32(s, state.lsn);
    ser_u32(s, count);

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

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

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

    setTimeout(() => sync_queue(state), config.sync_timeout);
}

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

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

            break;
        }

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

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

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

// Queue an event and initialize repated sends until ACKed
function queue_event(state, event, skip = false) {
    if (!state.online) { return; }

    push_event(state, event);

    if (skip) {
        return;
    }

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

    sync_queue(state);
}

// Fire and forget. Doesn't do anything if we are offline
async function fire_event(state, event) {
    if (!state.online) { return; }

    const s = serializer_create(4 + event_size(event));

    ser_u32(s, MESSAGE.FIRE);
    ser_event(s, event);

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

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

function color_event(color_u32) {
    return {
        'type': EVENT.SET_COLOR,
        'color': color_u32,
    };
}

function width_event(width) {
    return {
        'type': EVENT.SET_WIDTH,
        'width': width,
    };
}

function image_event(image_id, x, y, width, height) {
    return {
        'type': EVENT.IMAGE,
        'image_id': image_id,
        'x': x,
        'y': y,
        'width': width,
        'height': height,
    };
}

function image_move_event(image_id, x, y) {
    return {
        'type': EVENT.IMAGE_MOVE,
        'image_id': image_id,
        'x': x,
        'y': y,
    };
}

function image_scale_event(image_id, corner, x, y) {
    return {
        'type': EVENT.IMAGE_SCALE,
        'image_id': image_id,
        'corner': corner,
        'x': x,
        'y': y,
    };
}

function stroke_event(state) {
    const stroke = geometry_prepare_stroke(state);

    return { 
        'type': EVENT.STROKE,
        'points': stroke.points,
        'width': stroke.width,
        'color': stroke.color,
    };
}

function clear_event(state) {
    return {
        'type': EVENT.CLEAR
    };
}

function movecursor_event(x, y) {
    return  {
        'type': EVENT.MOVE_CURSOR,
        'x': x,
        'y': y,
    };
}

function movecanvas_event(state) {
    return {
        'type': EVENT.MOVE_CANVAS,
        'offset_x': state.canvas.offset.x,
        'offset_y': state.canvas.offset.y,
        'zoom_level': state.canvas.zoom_level,
    };
}

function zoomcanvas_event(state, zoom_cx, zoom_cy) {
    return {
        'type': EVENT.ZOOM_CANVAS,
        'zoom_level': state.canvas.zoom_level,
        'zoom_cx': zoom_cx,
        'zoom_cy': zoom_cy,
    };
}

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

function eraser_event(stroke_id) {
    return {
        'type': EVENT.ERASER,
        'stroke_id': stroke_id,
    }
}