path: root/circuitpython/devices/ble_hci/common-hal/_bleio/att.c

// Derived from ArduinoBLE.
// Copyright 2020 Dan Halbert for Adafruit Industries

// Some functions here are unused now, but may be used in the future.
// Don't warn or error about this, and depend on the compiler & linker to
// eliminate the associated code.
#pragma GCC diagnostic ignored "-Wunused"
#pragma GCC diagnostic ignored "-Wunused-function"

/*
  This file is part of the ArduinoBLE library.
  Copyright (c) 2018 Arduino SA. All rights reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "hci.h"
#include "att.h"

// Zephyr include files to define HCI communication values and structs.
// #include "hci_include/hci.h"
// #include "hci_include/hci_err.h"
#include "hci_include/att_internal.h"
#include "hci_include/l2cap_internal.h"

#include "py/obj.h"
#include "common-hal/_bleio/Adapter.h"
#include "common-hal/_bleio/Attribute.h"
#include "shared-bindings/_bleio/__init__.h"
#include "shared-bindings/_bleio/Characteristic.h"
#include "shared-bindings/_bleio/Descriptor.h"
#include "shared-bindings/_bleio/Service.h"
#include "shared-bindings/_bleio/UUID.h"
#include "supervisor/shared/tick.h"

STATIC uint16_t max_mtu = BT_ATT_DEFAULT_LE_MTU;  // 23
STATIC unsigned long timeout = 5000;

STATIC volatile bool confirm;

STATIC uint16_t long_write_handle = BLE_GATT_HANDLE_INVALID;
STATIC uint8_t *long_write_value = NULL;
STATIC uint16_t long_write_value_length = 0;

// When we send a request, fill this struct with info about the expected response.
// We check this against the actual received response.
STATIC struct {
    uint16_t conn_handle;       // Expected handle.
    uint8_t opcode;             // Expected RSP opcode.
    uint8_t *buffer;            // Pointer to response packet
    uint8_t length;             // Length of response packet.
} expected_rsp;

// A characteristic declaration has this data, in this order:
// See Bluetooth v5.1 spec, section 3.3.1 Characteristic declaration.
typedef struct __packed {
    uint8_t properties;
    uint16_t value_handle;
    uint8_t uuid[];  // 2 or 16 bytes
} characteristic_declaration_t;

STATIC uint8_t bleio_properties_to_ble_spec_properties(uint8_t bleio_properties) {
    uint8_t ble_spec_properties = 0;
    if (bleio_properties & CHAR_PROP_BROADCAST) {
        ble_spec_properties |= BT_GATT_CHRC_BROADCAST;
    }
    if (bleio_properties & CHAR_PROP_INDICATE) {
        ble_spec_properties |= BT_GATT_CHRC_INDICATE;
    }
    if (bleio_properties & CHAR_PROP_NOTIFY) {
        ble_spec_properties |= BT_GATT_CHRC_NOTIFY;
    }
    if (bleio_properties & CHAR_PROP_READ) {
        ble_spec_properties |= BT_GATT_CHRC_READ;
    }
    if (bleio_properties & CHAR_PROP_WRITE) {
        ble_spec_properties |= BT_GATT_CHRC_WRITE;
    }
    if (bleio_properties & CHAR_PROP_WRITE_NO_RESPONSE) {
        ble_spec_properties |= BT_GATT_CHRC_WRITE_WITHOUT_RESP;
    }

    return ble_spec_properties;
}

// FIX not currently used; reenable when used.
#if 0
STATIC uint8_t ble_spec_properties_to_bleio_properties(uint8_t ble_spec_properties) {
    uint8_t bleio_properties = 0;
    if (ble_spec_properties & BT_GATT_CHRC_BROADCAST) {
        bleio_properties |= CHAR_PROP_BROADCAST;
    }
    if (ble_spec_properties & BT_GATT_CHRC_INDICATE) {
        bleio_properties |= CHAR_PROP_INDICATE;
    }
    if (ble_spec_properties & BT_GATT_CHRC_NOTIFY) {
        bleio_properties |= CHAR_PROP_NOTIFY;
    }
    if (ble_spec_properties & BT_GATT_CHRC_READ) {
        bleio_properties |= CHAR_PROP_READ;
    }
    if (ble_spec_properties & BT_GATT_CHRC_WRITE) {
        bleio_properties |= CHAR_PROP_WRITE;
    }
    if (ble_spec_properties & BT_GATT_CHRC_WRITE_WITHOUT_RESP) {
        bleio_properties |= CHAR_PROP_WRITE_NO_RESPONSE;
    }

    return bleio_properties;
}
#endif // #if 0

STATIC void send_error(uint16_t conn_handle, uint8_t opcode, uint16_t handle, uint8_t code) {
    struct __packed {
        struct bt_att_hdr h;
        struct bt_att_error_rsp r;
    } rsp = { {
                  .code = BT_ATT_OP_ERROR_RSP,
              }, {
                  .request = opcode,
              }};

    hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, sizeof(rsp), (uint8_t *)&rsp);
}

STATIC void send_req(uint16_t conn_handle, size_t request_length, uint8_t *request_buffer) {
    hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, request_length, request_buffer);
}

STATIC int send_req_wait_for_rsp(uint16_t conn_handle, size_t request_length, uint8_t *request_buffer, uint8_t response_buffer[]) {
    // We expect a particular kind of response after this request.
    expected_rsp.conn_handle = conn_handle;
    // The response opcode is the request opcode + 1.
    expected_rsp.opcode = request_buffer[0] + 1;
    expected_rsp.buffer = response_buffer;
    expected_rsp.length = 0;

    send_req(conn_handle, request_length, request_buffer);

    if (response_buffer == NULL) {
        // not expecting a response.
        return 0;
    }

    for (uint64_t start = supervisor_ticks_ms64(); supervisor_ticks_ms64() - start < timeout;) {
        // RUN_BACKGROUND_TASKS includes hci_poll_for_incoming_pkt();
        RUN_BACKGROUND_TASKS;

        if (!att_handle_is_connected(conn_handle)) {
            break;
        }

        if (expected_rsp.length != 0) {
            expected_rsp.conn_handle = 0xffff;
            return expected_rsp.length;
        }
    }

    expected_rsp.conn_handle = 0xffff;
    return 0;
}

// If a response matches what is in expected_rsp, copy the rest of it into the buffer.
STATIC void check_and_save_expected_rsp(uint16_t conn_handle, uint8_t opcode, uint8_t dlen, uint8_t data[]) {
    if (conn_handle == expected_rsp.conn_handle && expected_rsp.opcode == opcode) {
        expected_rsp.buffer[0] = opcode;
        memcpy(&expected_rsp.buffer[1], data, dlen);
        expected_rsp.length = dlen + 1;
    }
}

void bleio_att_reset(void) {
    max_mtu = BT_ATT_DEFAULT_LE_MTU;
    timeout = 5000;
    long_write_handle = BLE_GATT_HANDLE_INVALID;
    long_write_value = NULL;
    long_write_value_length = 0;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        bleio_connections[i].conn_handle = BLE_CONN_HANDLE_INVALID;
        bleio_connections[i].role = 0x00;
        bleio_connections[i].addr.type = 0;
        memset(bleio_connections[i].addr.a.val, 0, sizeof_field(bt_addr_t, val));
        bleio_connections[i].mtu = BT_ATT_DEFAULT_LE_MTU;
    }
}

bool att_connect_to_address(bt_addr_le_t *addr) {
    // FIX
    if (hci_le_create_conn(0x0060, 0x0030, 0x00, addr, 0x00,
        0x0006, 0x000c, 0x0000, 0x00c8, 0x0004, 0x0006) != 0) {
        return false;
    }

    bool is_connected = false;

    for (uint64_t start = supervisor_ticks_ms64(); supervisor_ticks_ms64() - start < timeout;) {
        // RUN_BACKGROUND_TASKS includes hci_poll_for_incoming_pkt();
        RUN_BACKGROUND_TASKS;

        is_connected = att_address_is_connected(addr);

        if (is_connected) {
            break;
        }
    }

    if (!is_connected) {
        hci_le_cancel_conn();
    }

    return is_connected;
}

bool att_disconnect(uint16_t conn_handle) {
    if (conn_handle == BLE_CONN_HANDLE_INVALID) {
        return false;
    }

    hci_disconnect(conn_handle);

    // Confirm we're now disconnected.
    return !att_handle_is_connected(conn_handle);
}

// FIX
// STATIC bool discover_services(uint16_t conn_handle, BLERemoteDevice* device, const char* serviceUuidFilter) {
//     uint16_t reqStart_handle = 0x0001;
//     uint16_t reqEnd_handle = 0xffff;

//     uint8_t response_buffer[max_mtu];

//     BLEUuid serviceUuid(serviceUuidFilter);

//     while (reqEnd_handle == 0xffff) {
//         int respLength = readByGroupReq(conn_handle, reqStart_handle, reqEnd_handle, BLE_UUID_SERVICE_PRIMARY, response_buffer);

//         if (respLength == 0) {
//             return false;
//         }

//         if (response_buffer[0] == BT_ATT_OP_READ_GROUP_RSP) {
//             uint16_t lengthPerService = response_buffer[1];
//             uint8_t uuidLen = lengthPerService - 4;

//             for (size_t i = 2; i < respLength; i += lengthPerService) {
//                 struct __attribute__ ((packed)) RawService {
//                     uint16_t start_handle;
//                     uint16_t end_handle;
//                     uint8_t uuid[16];
//                 } *rawService = (RawService*)&response_buffer[i];

//                 if (serviceUuidFilter == NULL ||
//                     (uuidLen == serviceUuid.length() && memcmp(rawService->uuid, serviceUuid.data(), uuidLen) == 0)) {

//                     BLERemoteService* service = new BLERemoteService(rawService->uuid, uuidLen,
//                                                                      rawService->start_handle,
//                                                                      rawService->end_handle);

//                     if (service == NULL) {
//                         return false;
//                     }

//                     device->addService(service);

//                 }

//                 reqStart_handle = rawService->end_handle + 1;

//                 if (reqStart_handle == BLE_GATT_HANDLE_INVALID) {
//                     reqEnd_handle = BLE_GATT_HANDLE_INVALID;
//                 }
//             }
//         } else {
//             reqEnd_handle = BLE_GATT_HANDLE_INVALID;
//         }
//     }

//     return true;
// }

// STATIC bool discover_characteristics(uint16_t conn_handle, BLERemoteDevice* device) {
//     uint16_t reqStart_handle = 0x0001;
//     uint16_t reqEnd_handle = 0xffff;

//     uint8_t response_buffer[max_mtu];

//     int serviceCount = device->serviceCount();

//     for (size_t i = 0; i < serviceCount; i++) {
//         BLERemoteService* service = device->service(i);

//         reqStart_handle = service->start_handle();
//         reqEnd_handle = service->end_handle();

//         while (1) {
//             int respLength = readByTypeReq(conn_handle, reqStart_handle, reqEnd_handle, BLE_UUID_CHARACTERISTIC, response_buffer);

//             if (respLength == 0) {
//                 return false;
//             }

//             if (response_buffer[0] == BT_ATT_OP_READ_TYPE_RSP) {
//                 uint16_t lengthPerCharacteristic = response_buffer[1];
//                 uint8_t uuidLen = lengthPerCharacteristic - 5;

//                 for (size_t i = 2; i < respLength; i += lengthPerCharacteristic) {
//                     struct __attribute__ ((packed)) RawCharacteristic {
//                         uint16_t start_handle;
//                         uint8_t properties;
//                         uint16_t value_handle;
//                         uint8_t uuid[16];
//                     } *rawCharacteristic = (RawCharacteristic*)&response_buffer[i];

//                     BLERemoteCharacteristic* characteristic = new BLERemoteCharacteristic(rawCharacteristic->uuid, uuidLen,
//                                                                                           conn_handle,
//                                                                                           rawCharacteristic->start_handle,
//                                                                                           rawCharacteristic->properties,
//                                                                                           rawCharacteristic->value_handle);

//                     if (characteristic == NULL) {
//                         return false;
//                     }

//                     service->addCharacteristic(characteristic);

//                     reqStart_handle = rawCharacteristic->value_handle + 1;
//                 }
//             } else {
//                 break;
//             }
//         }
//     }

//     return true;
// }

// STATIC bool discover_descriptors(uint16_t conn_handle, BLERemoteDevice* device) {
//     uint16_t reqStart_handle = 0x0001;
//     uint16_t reqEnd_handle = 0xffff;

//     uint8_t response_buffer[max_mtu];

//     int serviceCount = device->serviceCount();

//     for (size_t i = 0; i < serviceCount; i++) {
//         BLERemoteService* service = device->service(i);

//         uint16_t serviceEnd_handle = service->end_handle();

//         int characteristicCount = service->characteristicCount();

//         for (int j = 0; j < characteristicCount; j++) {
//             BLERemoteCharacteristic* characteristic = service->characteristic(j);
//             BLERemoteCharacteristic* nextCharacteristic = (j == (characteristicCount - 1)) ? NULL : service->characteristic(j);

//             reqStart_handle = characteristic->value_handle() + 1;
//             reqEnd_handle = nextCharacteristic ? nextCharacteristic->value_handle() : serviceEnd_handle;

//             if (reqStart_handle > reqEnd_handle) {
//                 continue;
//             }

//             while (1) {
//                 int respLength = findInfoReq(conn_handle, reqStart_handle, reqEnd_handle, response_buffer);

//                 if (respLength == 0) {
//                     return false;
//                 }

//                 if (response_buffer[0] == BT_ATT_OP_FIND_INFO_RSP) {
//                     uint16_t lengthPerDescriptor = response_buffer[1] * 4;
//                     uint8_t uuidLen = 2;

//                     for (size_t i = 2; i < respLength; i += lengthPerDescriptor) {
//                         struct __attribute__ ((packed)) RawDescriptor {
//                             uint16_t handle;
//                             uint8_t uuid[16];
//                         } *rawDescriptor = (RawDescriptor*)&response_buffer[i];

//                         BLERemoteDescriptor* descriptor = new BLERemoteDescriptor(rawDescriptor->uuid, uuidLen,
//                                                                                   conn_handle,
//                                                                                   rawDescriptor->handle);

//                         if (descriptor == NULL) {
//                             return false;
//                         }

//                         characteristic->addDescriptor(descriptor);

//                         reqStart_handle = rawDescriptor->handle + 1;
//                     }
//                 } else {
//                     break;
//                 }
//             }
//         }
//     }

//     return true;
// }

bool att_discover_attributes(bt_addr_le_t *addr, const char *service_uuid_filter) {
    uint16_t conn_handle = att_conn_handle(addr);
    if (conn_handle == 0xffff) {
        return false;
    }

    // send MTU request
    if (!att_exchange_mtu(conn_handle)) {
        return false;
    }

    // find the device entry for the peeer
    // FIX BLERemoteDevice* device = NULL;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        //     if (bleio_connections[i].conn_handle == conn_handle) {
        //         //FIX if (bleio_connections[i].device == NULL) {
        //             //FIX
        //             //bleio_connections[i].device = new BLERemoteDevice();
        //         //}

        //         //device = bleio_connections[i].device;

        //         break;
        //     }
        // }

        // //FIX if (device == NULL) {
        // //     return false;
        // // }

        // if (service_uuid_filter == NULL) {
        //     // clear existing services
        //     //FIX device->clear_services();
        // } else {
        //     //FIX int service_count = device->service_count();

        //     for (size_t i = 0; i < service_count; i++) {
        //         //FIX BLERemoteService* service = device->service(i);

        //         if (strcasecmp(service->uuid(), service_uuid_filter) == 0) {
        //             // found an existing service with same UUID
        //             return true;
        //         }
        //     }
    }

    // discover services
    // FIX
    // if (!att_discover_services(conn_handle, device, service_uuid_filter)) {
    //     return false;
    // }

    // // discover characteristics
    // if (!discover_characteristics(conn_handle, device)) {
    //     return false;
    // }

    // // discover descriptors396
    // if (!discover_descriptors(conn_handle, device)) {
    //     return false;
    // }

    return true;
}

void att_set_max_mtu(uint16_t max_mtu_in) {
    max_mtu = max_mtu_in;
}

void att_set_timeout(unsigned long timeout_in) {
    timeout = timeout_in;
}

void att_add_connection(uint16_t handle, uint8_t role, bt_addr_le_t *peer_addr, uint16_t interval, uint16_t latency, uint16_t supervision_timeout, uint8_t master_clock_accuracy) {
    (void)interval;
    (void)latency;
    (void)supervision_timeout;
    (void)master_clock_accuracy;

    int peer_index = -1;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == 0xffff) {
            peer_index = i;
            break;
        }
    }

    if (peer_index == -1) {
        // bail, no space
        return;
    }

    bleio_connections[peer_index].conn_handle = handle;
    bleio_connections[peer_index].role = role;
    bleio_connections[peer_index].mtu = BT_ATT_DEFAULT_LE_MTU;
    memcpy(&bleio_connections[peer_index].addr, peer_addr, sizeof(bleio_connections[peer_index].addr));
}


void att_remove_connection(uint16_t conn_handle, uint8_t reason) {
    (void)reason;
    int peer_index = -1;
    int peer_count = 0;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == conn_handle) {
            peer_index = i;
        }

        if (bleio_connections[i].conn_handle != 0xffff) {
            peer_count++;
        }
    }

    if (peer_index == -1) {
        // Peer not found
        return;
    }

    if (peer_count == 1) {

        // Clear CCCD values on disconnect.
        size_t max_attribute_handle = bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj);
        for (size_t handle = 1; handle <= max_attribute_handle; handle++) {
            mp_obj_t attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);

            uint16_t zero = 0;
            mp_buffer_info_t zero_cccd_value = {
                .buf = &zero,
                .len = sizeof(zero),
            };

            if (mp_obj_is_type(attribute_obj, &bleio_descriptor_type)) {
                bleio_descriptor_obj_t *descriptor = MP_OBJ_TO_PTR(attribute_obj);
                if (bleio_uuid_get_uuid16_or_unknown(descriptor->uuid) == BLE_UUID_CCCD) {
                    common_hal_bleio_descriptor_set_value(descriptor, &zero_cccd_value);
                }
            }
        }

        long_write_handle = BLE_GATT_HANDLE_INVALID;
        long_write_value_length = 0;
    }

    bleio_connections[peer_index].conn_handle = 0xffff;
    bleio_connections[peer_index].role = 0x00;
    memset(&bleio_connections[peer_index].addr, 0x00, sizeof(bleio_connections[peer_index].addr));
    bleio_connections[peer_index].mtu = BT_ATT_DEFAULT_LE_MTU;
}

uint16_t att_conn_handle(bt_addr_le_t *addr) {
    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].addr.type == addr->type &&
            memcmp(&bleio_connections[i].addr.a.val, addr->a.val, sizeof(addr->a.val)) == 0) {
            return bleio_connections[i].conn_handle;
        }
    }

    return 0xffff;
}

bool att_is_connected(void) {
    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle != 0xffff) {
            return true;
        }
    }

    return false;
}

bool att_address_is_connected(bt_addr_le_t *addr) {
    return att_conn_handle(addr) != 0xffff;
}

bool att_handle_is_connected(uint16_t handle) {
    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == handle) {
            return true;
        }
    }

    return false;
}

uint16_t att_mtu(uint16_t handle) {
    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == handle) {
            return bleio_connections[i].mtu;
        }
    }

    return BT_ATT_DEFAULT_LE_MTU;
}

bool att_disconnect_all(void) {
    int num_disconnects = 0;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == 0xffff) {
            continue;
        }

        if (att_disconnect(bleio_connections[i].conn_handle) != 0) {
            continue;
        }

        num_disconnects++;

        bleio_connections[i].conn_handle = 0xffff;
        bleio_connections[i].role = 0x00;
        bleio_connections[i].addr.type = 0;
        memset(bleio_connections[i].addr.a.val, 0, sizeof(bleio_connections[i].addr.a.val));
        bleio_connections[i].mtu = BT_ATT_DEFAULT_LE_MTU;
    }

    return num_disconnects > 0;
}

bool att_notify(uint16_t handle, const uint8_t *value, int length) {
    int num_notifications = 0;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == 0xffff) {
            continue;
        }

        typedef struct __packed {
            struct bt_att_hdr hdr;
            struct bt_att_notify ntf;
        } notify_t;

        size_t allowed_length = MIN((uint16_t)(bleio_connections[i].mtu - sizeof(notify_t)), (uint16_t)length);

        uint8_t notify_bytes[sizeof(notify_t) + allowed_length];
        notify_t *notify = (notify_t *)notify_bytes;
        notify->hdr.code = BT_ATT_OP_NOTIFY;
        ;
        notify->ntf.handle = handle;
        memcpy(notify->ntf.value, value, allowed_length);
        hci_send_acl_pkt(bleio_connections[i].conn_handle, BT_L2CAP_CID_ATT,
            sizeof(notify_bytes), notify_bytes);

        num_notifications++;
    }

    return num_notifications > 0;
}

bool att_indicate(uint16_t handle, const uint8_t *value, int length) {
    int num_indications = 0;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == 0xffff) {
            continue;
        }

        typedef struct __packed {
            struct bt_att_hdr hdr;
            struct bt_att_indicate ind;
        } indicate_t;

        size_t allowed_length = MIN((uint16_t)(bleio_connections[i].mtu - sizeof(indicate_t)), (uint16_t)length);

        uint8_t indicate_bytes[sizeof(indicate_t) + allowed_length];
        indicate_t *indicate = (indicate_t *)indicate_bytes;
        indicate->hdr.code = BT_ATT_OP_INDICATE;
        ;
        indicate->ind.handle = handle;
        memcpy(indicate->ind.value, value, allowed_length);

        confirm = false;

        hci_send_acl_pkt(bleio_connections[i].conn_handle, BT_L2CAP_CID_ATT,
            sizeof(indicate_bytes), indicate_bytes);

        while (!confirm) {
            // RUN_BACKGROUND_TASKS includes hci_poll_for_incoming_pkt();
            RUN_BACKGROUND_TASKS;

            if (!att_address_is_connected(&bleio_connections[i].addr)) {
                break;
            }
        }

        num_indications++;
    }

    return num_indications > 0;
}

STATIC void process_error(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    struct bt_att_error_rsp *rsp = (struct bt_att_error_rsp *)data;

    if (dlen != sizeof(struct bt_att_error_rsp)) {
        // Incorrect size; ignore.
        return;
    }

    // expected_rsp.opcode is an RSP opcode. Does it match the REQ opcode in this response?
    if (expected_rsp.conn_handle == conn_handle && (expected_rsp.opcode - 1) == rsp->request) {
        expected_rsp.buffer[0] = BT_ATT_OP_ERROR_RSP;
        memcpy(&expected_rsp.buffer[1], data, dlen);
        expected_rsp.length = dlen + 1;
    }
}

STATIC void process_mtu_req(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    struct bt_att_exchange_mtu_req *req = (struct bt_att_exchange_mtu_req *)data;

    if (dlen != sizeof(struct bt_att_exchange_mtu_req)) {
        send_error(conn_handle, BT_ATT_OP_MTU_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    uint16_t mtu = req->mtu;

    if (mtu > max_mtu) {
        mtu = max_mtu;
    }

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == conn_handle) {
            bleio_connections[i].mtu = mtu;
            break;
        }
    }

    struct __packed {
        struct bt_att_hdr h;
        struct bt_att_exchange_mtu_rsp r;
    } rsp = { {
                  .code = BT_ATT_OP_MTU_RSP,
              }, {
                  .mtu = mtu,
              }};

    hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, sizeof(rsp), (uint8_t *)&rsp);
}

STATIC void process_mtu_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    struct bt_att_exchange_mtu_rsp *rsp = (struct bt_att_exchange_mtu_rsp *)data;

    if (dlen != sizeof(struct bt_att_exchange_mtu_rsp)) {
        return;
    }

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle == conn_handle) {
            bleio_connections[i].mtu = rsp->mtu;
            break;
        }
    }

    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_MTU_RSP, dlen, data);
}

STATIC void process_find_info_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_find_info_req *req = (struct bt_att_find_info_req *)data;

    if (dlen != sizeof(struct bt_att_find_info_req)) {
        send_error(conn_handle, BT_ATT_OP_FIND_INFO_REQ, req->start_handle, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_find_info_rsp r;
    } rsp_t;

    uint8_t rsp_bytes[mtu];
    rsp_t *rsp = (rsp_t *)rsp_bytes;
    rsp->h.code = BT_ATT_OP_FIND_INFO_RSP;

    // Keeps track of total length of the response.
    size_t rsp_length = sizeof(rsp_t);

    bool no_data = true;

    // All the data chunks must have uuid's that are the same size.
    // Keep track of the first one to make sure.
    size_t sizeof_first_uuid = 0;

    const uint16_t max_attribute_handle = bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj);
    for (uint16_t handle = req->start_handle;
         handle <= max_attribute_handle && handle <= req->end_handle;
         handle++) {

        mp_obj_t *attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);

        // Fetch the uuid for the given attribute, which might be a characteristic or a descriptor.
        bleio_uuid_obj_t *uuid;

        if (mp_obj_is_type(attribute_obj, &bleio_characteristic_type)) {
            bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute_obj);
            if (characteristic->handle != handle) {
                // If the handles don't match, this is the characteristic definition attribute.
                // Skip it. We want the characteristic value attribute.
                continue;
            }
            uuid = characteristic->uuid;

        } else {
            uuid = bleio_attribute_get_uuid(attribute_obj);
        }

        const uint32_t sizeof_uuid = common_hal_bleio_uuid_get_size(uuid) / 8;
        if (sizeof_first_uuid == 0) {
            sizeof_first_uuid = sizeof_uuid;
            // All the uuids in the response will be the same size.
            rsp->r.format = sizeof_uuid == 2 ? BT_ATT_INFO_16 : BT_ATT_INFO_128;
        }

        if (sizeof_uuid != sizeof_first_uuid) {
            // Previous UUID was a different size. We can't mix sizes.
            // Stop and send what we have so far.
            break;
        }

        if (rsp_length + sizeof_uuid > mtu) {
            // No remaining room in response for this uuid.
            break;
        }

        if (sizeof_uuid == 2) {
            struct bt_att_info_16 *info_16 = (struct bt_att_info_16 *)&rsp_bytes[rsp_length];
            info_16->handle = handle;
            info_16->uuid = common_hal_bleio_uuid_get_uuid16(uuid);

            rsp_length += sizeof(struct bt_att_info_16);
        } else {
            struct bt_att_info_128 *info_128 = (struct bt_att_info_128 *)&rsp_bytes[rsp_length];
            info_128->handle = handle;
            common_hal_bleio_uuid_get_uuid128(uuid, info_128->uuid);

            rsp_length += sizeof(struct bt_att_info_128);
        }

        no_data = false;
    } // end for


    if (no_data) {
        send_error(conn_handle, BT_ATT_OP_FIND_INFO_REQ, req->start_handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
    } else {
        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, rsp_length, rsp_bytes);
    }
}

static int att_find_info_req(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle, uint8_t response_buffer[]) {
    struct __packed req {
        struct bt_att_hdr h;
        struct bt_att_find_info_req r;
    } req = { {
                  .code = BT_ATT_OP_FIND_INFO_REQ,
              }, {
                  .start_handle = start_handle,
                  .end_handle = end_handle,
              }};

    return send_req_wait_for_rsp(conn_handle, sizeof(req), (uint8_t *)&req, response_buffer);
}

STATIC void process_find_info_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    if (dlen < 2) {
        return; // invalid, drop
    }

    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_FIND_INFO_RSP, dlen, data);
}

STATIC void process_find_type_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_find_type_req *req = (struct bt_att_find_type_req *)data;

    if (dlen < sizeof(struct bt_att_find_type_req)) {
        send_error(conn_handle, BT_ATT_OP_FIND_TYPE_RSP, req->start_handle, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    uint8_t response[mtu];
    uint16_t response_length;

    response[0] = BT_ATT_OP_FIND_TYPE_RSP;
    response_length = 1;

    // FIX
    // if (find_type_req->type == BLE_UUID_SERVICE_PRIMARY) {
    //     for (uint16_t i = (find_type_req->start_handle - 1); i < GATT.attributeCount() && i <= (find_type_req->end_handle - 1); i++) {
    //         BLELocalAttribute* attribute = GATT.attribute(i);

    //         if ((attribute->type() == find_type_req->type) && (attribute->uuidLength() == value_length) && memcmp(attribute->uuidData(), value, value_length) == 0) {
    //             BLELocalService* service = (BLELocalService*)attribute;

    //             // add the start handle
    //             uint16_t start_handle = service->start_handle();
    //             memcpy(&response[response_length], &start_handle, sizeof(start_handle));
    //             response_length += sizeof(start_handle);

    //             // add the end handle
    //             uint16_t end_handle = service->end_handle();
    //             memcpy(&response[response_length], &end_handle, sizeof(end_handle));
    //             response_length += sizeof(end_handle);
    //         }

    //         if ((response_length + 4) > mtu) {
    //             break;
    //         }
    //     }
    // }

    if (response_length == 1) {
        send_error(conn_handle, BT_ATT_OP_FIND_TYPE_RSP, req->start_handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
    } else {
        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, response_length, response);
    }
}

static void process_read_group_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_read_group_req *req = (struct bt_att_read_group_req *)data;
    uint16_t type_uuid = req->uuid[0] | (req->uuid[1] << 8);

    // We only support returning services for BT_ATT_OP_READ_GROUP_REQ, which is typically used
    // for service discovery.
    if (dlen != sizeof(struct bt_att_read_group_req) + sizeof(type_uuid) ||
        (type_uuid != BLE_UUID_SERVICE_PRIMARY &&
         type_uuid != BLE_UUID_SERVICE_SECONDARY)) {
        send_error(conn_handle, BT_ATT_OP_READ_GROUP_REQ, req->start_handle, BT_ATT_ERR_UNSUPPORTED_GROUP_TYPE);
        return;
    }

    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_group_rsp r;
    } rsp_t;

    uint8_t rsp_bytes[mtu];
    rsp_t *rsp = (rsp_t *)rsp_bytes;
    rsp->h.code = BT_ATT_OP_READ_GROUP_RSP;
    rsp->r.len = 0;

    // Keeps track of total length of the response.
    size_t rsp_length = sizeof(rsp_t);

    bool no_data = true;

    // All the data chunks must have uuid's that are the same size.
    // Keep track of the first one to make sure.
    size_t sizeof_first_service_uuid = 0;

    // Size of a single bt_att_group_data chunk. Start with the intial size, and
    // add the uuid size in the loop below.
    size_t data_length = sizeof(struct bt_att_group_data);

    const uint16_t max_attribute_handle = bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj);
    for (uint16_t handle = req->start_handle;
         handle <= max_attribute_handle && handle <= req->end_handle;
         handle++) {

        if (rsp_length + data_length > mtu) {
            // The next possible bt_att_group_data chunk won't fit. The response is full.
            break;
        }

        mp_obj_t *attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);
        if (mp_obj_is_type(attribute_obj, &bleio_service_type)) {
            bleio_service_obj_t *service = MP_OBJ_TO_PTR(attribute_obj);

            // Is this a 16-bit or a 128-bit uuid? It must match in size with any previous attribute
            // in this transmission.
            const uint32_t sizeof_service_uuid = common_hal_bleio_uuid_get_size(service->uuid) / 8;
            if (sizeof_first_service_uuid == 0) {
                sizeof_first_service_uuid = sizeof_service_uuid;
                data_length += sizeof_service_uuid;
            } else if (sizeof_first_service_uuid != sizeof_service_uuid) {
                // Mismatched sizes, which can't be in the same batch.
                // Transmit just what we have so far in this batch.
                break;
            }

            // Pass the length of ONE bt_att_group_data chunk.
            // There may be multiple chunks in this transmission.
            rsp->r.len = data_length;

            struct bt_att_group_data *group_data = (struct bt_att_group_data *)&rsp_bytes[rsp_length];

            group_data->start_handle = service->start_handle;
            group_data->end_handle = service->end_handle;
            common_hal_bleio_uuid_pack_into(service->uuid, group_data->value);

            rsp_length += data_length;
            no_data = false;
        }
    }

    if (no_data) {
        send_error(conn_handle, BT_ATT_OP_READ_GROUP_REQ, req->start_handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
    } else {
        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, rsp_length, rsp_bytes);
    }
}

static int att_read_group_req(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle, uint16_t uuid, uint8_t response_buffer[]) {

    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_group_req r;
    } req_t;

    uint8_t req_bytes[sizeof(req_t) + sizeof(uuid)];
    req_t *req = (req_t *)req_bytes;

    req->h.code = BT_ATT_OP_READ_GROUP_REQ;
    req->r.start_handle = start_handle;
    req->r.end_handle = end_handle;
    req->r.uuid[0] = uuid & 0xff;
    req->r.uuid[1] = uuid >> 8;

    return send_req_wait_for_rsp(conn_handle, sizeof(req_bytes), req_bytes, response_buffer);
}

STATIC void process_read_group_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    if (dlen < 2) {
        return; // invalid, drop
    }

    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_READ_GROUP_RSP, dlen, data);
}

STATIC void process_read_or_read_blob_req(uint16_t conn_handle, uint16_t mtu, uint8_t opcode, uint8_t dlen, uint8_t data[]) {
    uint16_t handle;
    uint16_t offset = 0;
    uint8_t response_opcode;

    if (opcode == BT_ATT_OP_READ_REQ) {
        if (dlen != sizeof(struct bt_att_read_req)) {
            send_error(conn_handle, BT_ATT_OP_READ_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
            return;
        }

        struct bt_att_read_req *req = (struct bt_att_read_req *)data;
        handle = req->handle;
        response_opcode = BT_ATT_OP_READ_RSP;

    } else if (opcode == BT_ATT_OP_READ_BLOB_REQ) {
        if (dlen != sizeof(struct bt_att_read_blob_req)) {
            send_error(conn_handle, BT_ATT_OP_READ_BLOB_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
            return;
        }

        struct bt_att_read_blob_req *req = (struct bt_att_read_blob_req *)data;
        handle = req->handle;
        offset = req->offset;
        response_opcode = BT_ATT_OP_READ_BLOB_RSP;
    } else {
        return;
    }


    if (handle > bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj)) {
        send_error(conn_handle, opcode, handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
        return;
    }

    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_rsp r; // Same as bt_att_read_blob_rsp.
    } rsp_t;

    uint8_t rsp_bytes[mtu];
    rsp_t *rsp = (rsp_t *)rsp_bytes;
    rsp->h.code = response_opcode;

    // Keeps track of total length of the response.
    size_t rsp_length = sizeof(rsp_t);

    mp_obj_t *attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);
    if (mp_obj_is_type(attribute_obj, &bleio_service_type)) {
        if (offset) {
            send_error(conn_handle, BT_ATT_ERR_ATTRIBUTE_NOT_LONG, handle, BT_ATT_ERR_INVALID_PDU);
            return;
        }

        bleio_service_obj_t *service = MP_OBJ_TO_PTR(attribute_obj);
        const uint32_t sizeof_service_uuid = common_hal_bleio_uuid_get_size(service->uuid) / 8;

        common_hal_bleio_uuid_pack_into(service->uuid, rsp->r.value);
        rsp_length += sizeof_service_uuid;

    } else if (mp_obj_is_type(attribute_obj, &bleio_characteristic_type)) {
        bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute_obj);
        if (characteristic->decl_handle == handle) {
            // Read characteristic declaration. Return properties, value handle, and uuid.
            if (offset) {
                send_error(conn_handle, opcode, handle, BT_ATT_ERR_ATTRIBUTE_NOT_LONG);
                return;
            }

            characteristic_declaration_t *char_decl = (characteristic_declaration_t *)rsp->r.value;

            // Convert from the bleio properties bit values to the BLE spec properties bit values.
            // They are not the same :(.
            char_decl->properties = bleio_properties_to_ble_spec_properties(characteristic->props);
            char_decl->value_handle = characteristic->handle;

            const uint32_t sizeof_char_uuid = common_hal_bleio_uuid_get_size(characteristic->uuid) / 8;
            common_hal_bleio_uuid_pack_into(characteristic->uuid, char_decl->uuid);
            rsp_length += sizeof_char_uuid;

        } else {
            // Read characteristic value.

            if ((characteristic->props & CHAR_PROP_READ) == 0) {
                send_error(conn_handle, opcode, handle, BT_ATT_ERR_READ_NOT_PERMITTED);
                return;
            }

            mp_buffer_info_t bufinfo;
            mp_get_buffer(characteristic->value, &bufinfo, MP_BUFFER_READ);

            if (offset >= bufinfo.len) {
                send_error(conn_handle, opcode, handle, BT_ATT_ERR_INVALID_OFFSET);
                return;
            }

            size_t value_length = MIN(mtu - rsp_length, bufinfo.len - offset);
            memcpy(rsp->r.value, bufinfo.buf + offset, value_length);
            rsp_length += value_length;
        }
    } else if (mp_obj_is_type(attribute_obj, &bleio_descriptor_type)) {
        bleio_descriptor_obj_t *descriptor = MP_OBJ_TO_PTR(attribute_obj);

        mp_buffer_info_t bufinfo;
        mp_get_buffer(descriptor->value, &bufinfo, MP_BUFFER_READ);

        if (offset >= bufinfo.len) {
            send_error(conn_handle, opcode, handle, BT_ATT_ERR_INVALID_OFFSET);
            return;
        }

        size_t value_length = MIN(mtu - rsp_length, bufinfo.len - offset);
        memcpy(rsp->r.value, bufinfo.buf + offset, value_length);
        rsp_length += value_length;
    }

    hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, rsp_length, rsp_bytes);
}

STATIC void process_read_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_READ_RSP, dlen, data);
}

STATIC void process_read_type_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_read_type_req *req = (struct bt_att_read_type_req *)data;
    uint16_t type_uuid = req->uuid[0] | (req->uuid[1] << 8);

    if (dlen != sizeof(struct bt_att_read_type_req) + sizeof(type_uuid)) {
        send_error(conn_handle, BT_ATT_OP_READ_TYPE_REQ, req->start_handle, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_type_rsp r;
    } rsp_t;

    uint8_t rsp_bytes[mtu];
    rsp_t *rsp = (rsp_t *)rsp_bytes;
    rsp->h.code = BT_ATT_OP_READ_TYPE_RSP;
    rsp->r.len = 0;

    // Keeps track of total length of the response.
    size_t rsp_length = sizeof(rsp_t);

    bool no_data = true;

    // All the data chunks must have uuid's that are the same size.
    // Keep track of the first one to make sure.
    size_t sizeof_first_uuid = 0;

    // Size of a single bt_att_data chunk. Start with the initial size, and
    // add the uuid size and other data sizes in the loop below.
    size_t data_length = sizeof(struct bt_att_data);

    const uint16_t max_attribute_handle = bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj);
    for (uint16_t handle = req->start_handle;
         handle <= max_attribute_handle && handle <= req->end_handle;
         handle++) {

        if (rsp_length + data_length > mtu) {
            // The next possible bt_att_data chunk won't fit. The response is full.
            break;
        }

        mp_obj_t *attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);

        if (type_uuid == BLE_UUID_CHARACTERISTIC &&
            mp_obj_is_type(attribute_obj, &bleio_characteristic_type)) {
            // Request is for characteristic declarations.
            bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute_obj);

            if (characteristic->handle == handle) {
                // If the characteristic's handle is this attribute's handle, skip it:
                // it's the attribute for characteristic value. We want to return the declaration
                // handle attribute instead. (It will probably get skipped below, by the
                // handle++).
                continue;
            }

            // Is this a 16-bit or a 128-bit uuid? It must match in size with any previous attribute
            // in this transmission.
            const uint32_t sizeof_uuid = common_hal_bleio_uuid_get_size(characteristic->uuid) / 8;
            if (sizeof_first_uuid == 0) {
                sizeof_first_uuid = sizeof_uuid;
                data_length += sizeof_uuid;
                data_length += sizeof(characteristic_declaration_t);
            } else if (sizeof_first_uuid != sizeof_uuid) {
                // Mismatched sizes, which can't be in the same batch.
                // Transmit just what we have so far in this batch.
                break;
            }

            // Pass the length of ONE bt_att_data chunk.
            // There may be multiple chunks in this transmission.
            rsp->r.len = data_length;

            struct bt_att_data *att_data = (struct bt_att_data *)&rsp_bytes[rsp_length];

            att_data->handle = characteristic->decl_handle;

            characteristic_declaration_t *char_decl = (characteristic_declaration_t *)att_data->value;

            // Convert from the bleio properties bit values to the BLE spec properties bit values.
            // They are not the same :(.
            char_decl->properties = bleio_properties_to_ble_spec_properties(characteristic->props);
            char_decl->value_handle = characteristic->handle;
            common_hal_bleio_uuid_pack_into(characteristic->uuid, char_decl->uuid);

            // We know the next handle will be the characteristic value handle, so skip it.
            handle++;

            rsp_length += data_length;
            no_data = false;

        } else if (mp_obj_is_type(attribute_obj, &bleio_descriptor_type)) {
            // See if request is for a descriptor value with a 16-bit UUID, such as the CCCD.
            bleio_descriptor_obj_t *descriptor = MP_OBJ_TO_PTR(attribute_obj);
            if (bleio_uuid_get_uuid16_or_unknown(descriptor->uuid) == type_uuid) {
                struct bt_att_data *att_data = (struct bt_att_data *)&rsp_bytes[rsp_length];

                att_data->handle = handle;

                mp_buffer_info_t bufinfo;
                if (!mp_get_buffer(descriptor->value, &bufinfo, MP_BUFFER_READ)) {
                    break;
                }
                uint16_t value_size = MIN(mtu - rsp_length, bufinfo.len);
                memcpy(att_data->value, bufinfo.buf, value_size);
                rsp_length += value_size;

                // Only return one descriptor value.
                no_data = false;
                break;
            }

        } else if (mp_obj_is_type(attribute_obj, &bleio_characteristic_type)) {
            // See if request is for a characteristic value with a 16-bit UUID.
            bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute_obj);
            if (bleio_uuid_get_uuid16_or_unknown(characteristic->uuid) == type_uuid) {

                struct bt_att_data *att_data = (struct bt_att_data *)&rsp_bytes[rsp_length];

                att_data->handle = handle;

                mp_buffer_info_t bufinfo;
                if (!mp_get_buffer(characteristic->value, &bufinfo, MP_BUFFER_READ)) {
                    // This shouldn't happen. There should be a buf in characteristic->value.
                    break;
                }
                uint16_t value_size = MIN(mtu - rsp_length, bufinfo.len);
                memcpy(att_data->value, bufinfo.buf, value_size);
                rsp_length += value_size;

                // Only return one characteristic value.
                no_data = false;
                break;
            }
        }
    } // end for loop

    if (no_data) {
        send_error(conn_handle, BT_ATT_OP_READ_TYPE_REQ,
            req->start_handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
    } else {
        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, rsp_length, rsp_bytes);
    }
}

static int att_read_type_req(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle, uint16_t type, uint8_t response_buffer[]) {
    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_type_req r;
    } req_t;

    uint8_t req_bytes[sizeof(req_t) + sizeof(type)];
    req_t *req = (req_t *)req_bytes;

    req->h.code = BT_ATT_OP_READ_TYPE_REQ;
    req->r.start_handle = start_handle;
    req->r.end_handle = end_handle;
    req->r.uuid[0] = type & 0xff;
    req->r.uuid[1] = type >> 8;

    return send_req_wait_for_rsp(conn_handle, sizeof(req_bytes), req_bytes, response_buffer);
}

STATIC void process_read_type_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    if (dlen < 1) {
        return; // invalid, drop
    }

    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_READ_TYPE_RSP, dlen, data);
}

// Handles BT_ATT_OP_WRITE_REQ or BT_ATT_OP_WRITE_
STATIC void process_write_req_or_cmd(uint16_t conn_handle, uint16_t mtu, uint8_t op, uint8_t dlen, uint8_t data[]) {
    // struct bt_att_write_cmd is identical, so don't bother to split code paths based on opcode.
    struct bt_att_write_req *req = (struct bt_att_write_req *)data;

    bool with_response = (op == BT_ATT_OP_WRITE_REQ);

    if (dlen < sizeof(struct bt_att_write_req)) {
        if (with_response) {
            send_error(conn_handle, BT_ATT_OP_WRITE_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
        }
        return;
    }

    if (req->handle > bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj)) {
        if (with_response) {
            send_error(conn_handle, BT_ATT_OP_WRITE_REQ, req->handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
        }
        return;
    }

    size_t value_length = dlen - sizeof(struct bt_att_write_req);

    mp_buffer_info_t bufinfo;
    bufinfo.buf = req->value;
    bufinfo.len = value_length;

    mp_obj_t attribute_obj = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, req->handle);

    if (mp_obj_is_type(attribute_obj, &bleio_characteristic_type)) {
        bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute_obj);

        //  Don't write the characteristic declaration.
        // Also, this must be a writable characteristic.
        if (req->handle != characteristic->handle ||
            (with_response
             ? (characteristic->props & CHAR_PROP_WRITE) == 0
             : (characteristic->props & CHAR_PROP_WRITE_NO_RESPONSE) == 0)) {
            if (with_response) {
                send_error(conn_handle, BT_ATT_OP_WRITE_REQ, req->handle, BT_ATT_ERR_WRITE_NOT_PERMITTED);
            }
            return;
        }

        // Just change the local value. Don't fire off notifications, etc.
        bleio_characteristic_set_local_value(characteristic, &bufinfo);

    } else if (mp_obj_is_type(attribute_obj, &bleio_descriptor_type)) {
        bleio_descriptor_obj_t *descriptor = MP_OBJ_TO_PTR(attribute_obj);
        // Only CCCD's are writable.
        if (bleio_uuid_get_uuid16_or_unknown(descriptor->uuid) != BLE_UUID_CCCD) {
            if (with_response) {
                send_error(conn_handle, BT_ATT_OP_WRITE_REQ, req->handle, BT_ATT_ERR_WRITE_NOT_PERMITTED);
            }
            return;
        }

        common_hal_bleio_descriptor_set_value(descriptor, &bufinfo);
    }

    if (with_response) {
        // There's no data in the response. We just indicate the write happened.
        struct bt_att_hdr rsp = {
            .code = BT_ATT_OP_WRITE_RSP,
        };

        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, sizeof(rsp), (uint8_t *)&rsp);
    }
}

STATIC void process_write_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    if (dlen != 0) {
        return; // drop
    }

    check_and_save_expected_rsp(conn_handle, BT_ATT_OP_WRITE_RSP, dlen, data);
}

STATIC void process_prepare_write_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_prepare_write_req *req = (struct bt_att_prepare_write_req *)data;

    if (dlen < sizeof(struct bt_att_prepare_write_req)) {
        send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    uint16_t handle = req->handle;
    uint16_t offset = req->offset;
    (void)offset;

    if (handle > bleio_adapter_max_attribute_handle(&common_hal_bleio_adapter_obj)) {
        send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_ATTRIBUTE_NOT_FOUND);
        return;
    }

    mp_obj_t *attribute = bleio_adapter_get_attribute(&common_hal_bleio_adapter_obj, handle);

    if (!mp_obj_is_type(attribute, &bleio_characteristic_type)) {
        send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_ATTRIBUTE_NOT_LONG);
        return;
    }

    bleio_characteristic_obj_t *characteristic = MP_OBJ_TO_PTR(attribute);

    if (handle != characteristic->handle) {
        send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_ATTRIBUTE_NOT_LONG);
        return;
    }

    if ((characteristic->props & CHAR_PROP_WRITE) == 0) {
        send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_WRITE_NOT_PERMITTED);
        return;
    }

    // FIX if (long_write_handle == BLE_GATT_HANDLE_INVALID)
    //     int valueSize = characteristic->valueSize();

    //     long_write_value = (uint8_t*)realloc(long_write_value, valueSize);
    //     long_write_value_length = 0;
    //     long_write_handle = handle;

    //     memset(long_write_value, 0x00, valueSize);
    // } else if (long_write_handle != handle) {
    //     send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_UNLIKELY);
    //     return;
    // }

    // uint8_t value_length = dlen - sizeof(struct bt_att_prepare_write_req);
    // uint8_t* value = &data[sizeof(struct bt_att_prepare_write_req)];

    // if ((offset != long_write_value_length) || ((offset + value_length) > (uint16_t)characteristic->valueSize())) {
    //     send_error(conn_handle, BT_ATT_OP_PREPARE_WRITE_REQ, handle, BT_ATT_ERR_INVALID_OFFSET);
    //     return;
    // }

    // memcpy(long_write_value + offset, value, value_length);
    // long_write_value_length += value_length;

    // uint8_t response[mtu];
    // uint16_t response_length;

    // response[0] = BT_ATT_OP_PREP_WRITE_RSP;
    // memcpy(&response[1], data, dlen);
    // response_length = dlen + 1;

    // hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, response_length, response);
}

STATIC void process_exec_write_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, uint8_t data[]) {
    struct bt_att_exec_write_req *req = (struct bt_att_exec_write_req *)data;

    if (dlen != sizeof(struct bt_att_exec_write_req)) {
        send_error(conn_handle, BT_ATT_OP_EXEC_WRITE_REQ, BLE_GATT_HANDLE_INVALID, BT_ATT_ERR_INVALID_PDU);
        return;
    }

    if (long_write_handle && (req->flags & 0x01)) {
        // FIX BLELocalCharacteristic* characteristic = (BLELocalCharacteristic*)GATT.attribute(long_write_handle - 1);

        for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
            if (bleio_connections[i].conn_handle == conn_handle) {
                // FIX characteristic->writeValue(BLEDevice(bleio_connections[i].address_type, bleio_connections[i].address), long_write_value, long_write_value_length);
                break;
            }
        }
    }

    long_write_handle = BLE_GATT_HANDLE_INVALID;
    long_write_value_length = 0;

    uint8_t response[mtu];
    uint16_t response_length;

    response[0] = BT_ATT_OP_EXEC_WRITE_RSP;
    response_length = 1;

    hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, response_length, response);
}

STATIC void process_notify_or_indicate(uint16_t conn_handle, uint8_t opcode, uint8_t dlen, uint8_t data[]) {
    if (dlen < 2) {
        return; // drop
    }

    // struct bt_att_notify and bt_att_indicate are identical.
    // FIXunused struct bt_att_notify *req = (struct bt_att_notify *) data;

    // FIXunused uint8_t handle = req->handle;

    for (size_t i = 0; i < BLEIO_TOTAL_CONNECTION_COUNT; i++) {
        if (bleio_connections[i].conn_handle != conn_handle) {
            continue;
        }

        // FIX BLERemoteDevice* device = bleio_connections[i].device;

        // if (!device) {
        //     break;
        // }

        // int serviceCount = device->serviceCount();

        // for (size_t i = 0; i < serviceCount; i++) {
        //     BLERemoteService* s = device->service(i);

        //     if (s->start_handle() < handle && s->end_handle() >= handle) {
        //         int characteristicCount = s->characteristicCount();

        //         for (int j = 0; j < characteristicCount; j++) {
        //             BLERemoteCharacteristic* c = s->characteristic(j);

        //             if (c->value_handle() == handle) {
        //                 //FIX c->writeValue(BLEDevice(bleio_connections[i].address_type, bleio_connections[i].address), &data[2], dlen - 2);
        //             }
        //         }

        //         break;
        //     }
        // }
    }

    if (opcode == BT_ATT_OP_INDICATE) {
        // send CONFIRM for INDICATE

        uint8_t op_confirm = BT_ATT_OP_CONFIRM;

        hci_send_acl_pkt(conn_handle, BT_L2CAP_CID_ATT, sizeof(op_confirm), &op_confirm);
    }
}

STATIC void process_confirm(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    (void)conn_handle;
    (void)dlen;
    (void)data;

    confirm = true;
}

bool att_exchange_mtu(uint16_t conn_handle) {
    uint8_t response_buffer[max_mtu];
    struct bt_att_exchange_mtu_req req = {
        .mtu = max_mtu,
    };
    return send_req_wait_for_rsp(conn_handle, sizeof(req), (uint8_t *)&req, response_buffer);
}

int att_read_req(uint16_t conn_handle, uint16_t handle, uint8_t response_buffer[]) {
    struct __packed {
        struct bt_att_hdr h;
        struct bt_att_read_req r;
    } req = { {
                  .code = BT_ATT_OP_READ_REQ,
              }, {
                  .handle = handle,
              }};

    return send_req_wait_for_rsp(conn_handle, sizeof(req), (uint8_t *)&req, response_buffer);
}

int att_write_req(uint16_t conn_handle, uint16_t handle, const uint8_t *data, uint8_t data_len, uint8_t response_buffer[]) {
    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_write_req r;
    } req_t;

    uint8_t req_bytes[sizeof(req_t) + data_len];
    req_t *req = (req_t *)req_bytes;
    req->h.code = BT_ATT_OP_WRITE_REQ;
    req->r.handle = handle;
    memcpy(req->r.value, data, data_len);

    return send_req_wait_for_rsp(conn_handle, sizeof(req_bytes), req_bytes, response_buffer);
}

void att_write_cmd(uint16_t conn_handle, uint16_t handle, const uint8_t *data, uint8_t data_len) {
    typedef struct __packed {
        struct bt_att_hdr h;
        struct bt_att_write_cmd r;
    } cmd_t;

    uint8_t cmd_bytes[sizeof(cmd_t) + data_len];
    cmd_t *cmd = (cmd_t *)cmd_bytes;
    cmd->h.code = BT_ATT_OP_WRITE_CMD;
    cmd->r.handle = handle;
    memcpy(cmd->r.value, data, data_len);

    send_req(conn_handle, sizeof(cmd_bytes), cmd_bytes);
}

void att_process_data(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
    // Opcode is a single byte at the front of the data.
    uint8_t opcode = data[0];

    // Skip over opcode.
    dlen--;
    data++;

    uint16_t mtu = att_mtu(conn_handle);

    switch (opcode) {
        case BT_ATT_OP_ERROR_RSP:
            process_error(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_MTU_REQ:
            process_mtu_req(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_MTU_RSP:
            process_mtu_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_FIND_INFO_REQ:
            process_find_info_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_FIND_INFO_RSP:
            process_find_info_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_FIND_TYPE_REQ:
            process_find_type_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_READ_TYPE_REQ:
            process_read_type_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_READ_TYPE_RSP:
            process_read_type_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_READ_GROUP_REQ:
            process_read_group_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_READ_GROUP_RSP:
            process_read_group_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_READ_REQ:
        case BT_ATT_OP_READ_BLOB_REQ:
            process_read_or_read_blob_req(conn_handle, mtu, opcode, dlen, data);
            break;

        case BT_ATT_OP_READ_RSP:
            process_read_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_WRITE_REQ:
        case BT_ATT_OP_WRITE_CMD:
            process_write_req_or_cmd(conn_handle, mtu, opcode, dlen, data);
            break;

        case BT_ATT_OP_WRITE_RSP:
            process_write_rsp(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_PREPARE_WRITE_REQ:
            process_prepare_write_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_EXEC_WRITE_REQ:
            process_exec_write_req(conn_handle, mtu, dlen, data);
            break;

        case BT_ATT_OP_NOTIFY:
        case BT_ATT_OP_INDICATE:
            process_notify_or_indicate(conn_handle, opcode, dlen, data);
            break;

        case BT_ATT_OP_CONFIRM:
            process_confirm(conn_handle, dlen, data);
            break;

        case BT_ATT_OP_READ_MULT_REQ:
        case BT_ATT_OP_SIGNED_WRITE_CMD:
        default:
            send_error(conn_handle, opcode, 0x00, BT_ATT_ERR_NOT_SUPPORTED);
            break;
    }
}

// FIX Do we need all of these?
static void check_att_err(uint8_t err) {
    const compressed_string_t *msg = NULL;
    switch (err) {
        case 0:
            return;
        case BT_ATT_ERR_INVALID_HANDLE:
            msg = translate("Invalid handle");
            break;
        case BT_ATT_ERR_READ_NOT_PERMITTED:
            msg = translate("Read not permitted");
            break;
        case BT_ATT_ERR_WRITE_NOT_PERMITTED:
            msg = translate("Write not permitted");
            break;
        case BT_ATT_ERR_INVALID_PDU:
            msg = translate("Invalid PDU");
            break;
        case BT_ATT_ERR_NOT_SUPPORTED:
            msg = translate("Not supported");
            break;
        case BT_ATT_ERR_INVALID_OFFSET:
            msg = translate("Invalid offset");
            break;
        case BT_ATT_ERR_PREPARE_QUEUE_FULL:
            msg = translate("Prepare queue full");
            break;
        case BT_ATT_ERR_ATTRIBUTE_NOT_FOUND:
            msg = translate("Attribute not found");
            break;
        case BT_ATT_ERR_ATTRIBUTE_NOT_LONG:
            msg = translate("Attribute not long");
            break;
        case BT_ATT_ERR_ENCRYPTION_KEY_SIZE:
            msg = translate("Encryption key size");
            break;
        case BT_ATT_ERR_INVALID_ATTRIBUTE_LEN:
            msg = translate("Invalid attribute length");
            break;
        case BT_ATT_ERR_UNLIKELY:
            msg = translate("Unlikely");
            break;
        case BT_ATT_ERR_UNSUPPORTED_GROUP_TYPE:
            msg = translate("Unsupported group type");
            break;
        case BT_ATT_ERR_INSUFFICIENT_RESOURCES:
            msg = translate("Insufficient resources");
            break;
        case BT_ATT_ERR_DB_OUT_OF_SYNC:
            msg = translate("DB out of sync");
            break;
        case BT_ATT_ERR_VALUE_NOT_ALLOWED:
            msg = translate("Value not allowed");
            break;
    }
    if (msg) {
        mp_raise_bleio_BluetoothError(msg);
    }

    switch (err) {
        case BT_ATT_ERR_AUTHENTICATION:
            msg = translate("Insufficient authentication");
            break;
        case BT_ATT_ERR_INSUFFICIENT_ENCRYPTION:
            msg = translate("Insufficient encryption");
            break;
    }
    if (msg) {
        mp_raise_bleio_SecurityError(msg);
    }

    mp_raise_bleio_BluetoothError(translate("Unknown ATT error: 0x%02x"), err);
}