// SPDX-License-Identifier: GPL-2.0-or-later
//
// KeyOverlay: lets the host ask which layer is active.
//
// Request  (host -> keyboard): [0xE0, 0x01, ...]
// Response (keyboard -> host): [0xE0, 0x01, highest_layer, layer_state (u32 LE), default_layer_state (u32 LE), ...]
//
// 0xE0 is outside the ids used by VIA (0x01..0x1F), Vial (0xFE) and "unhandled" (0xFF).
// Only reads state; it changes nothing on the keyboard and works while Vial is locked.
#include QMK_KEYBOARD_H
#include "raw_hid.h"
#include <string.h>

#define KEYOVERLAY_CMD 0xE0
#define KEYOVERLAY_PROTOCOL 0x01
#define KEYOVERLAY_ID_UNHANDLED 0xFF
#define KEYOVERLAY_MIN_LENGTH 11

void raw_hid_receive_kb(uint8_t *data, uint8_t length) {
    if (data[0] != KEYOVERLAY_CMD || length < KEYOVERLAY_MIN_LENGTH) {
        data[0] = KEYOVERLAY_ID_UNHANDLED;
        return;
    }
    const uint32_t active  = (uint32_t)layer_state;
    const uint32_t default_ = (uint32_t)default_layer_state;

    data[1] = KEYOVERLAY_PROTOCOL;
    data[2] = get_highest_layer(layer_state | default_layer_state);
    memcpy(&data[3], &active, sizeof(active));
    memcpy(&data[7], &default_, sizeof(default_));
}