/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/*
  support for serial connected AHRS systems
 */

#define ALLOW_DOUBLE_MATH_FUNCTIONS

#include "AP_ExternalAHRS_config.h"

#if AP_EXTERNAL_AHRS_VECTORNAV_ENABLED

#include "AP_ExternalAHRS_VectorNav.h"
#include <AP_Math/AP_Math.h>
#include <AP_Math/crc.h>
#include <AP_Baro/AP_Baro.h>
#include <AP_Compass/AP_Compass.h>
#include <AP_GPS/AP_GPS.h>
#include <AP_InertialSensor/AP_InertialSensor.h>
#include <GCS_MAVLink/GCS.h>
#include <AP_Logger/AP_Logger.h>
#include <AP_SerialManager/AP_SerialManager.h>
#include <AP_Common/NMEA.h>
#include <stdio.h>
#include <AP_BoardConfig/AP_BoardConfig.h>

extern const AP_HAL::HAL &hal;

/*
  header for pre-configured 50Hz data
  assumes the following config for VN-300:
    $VNWRG,75,3,8,34,072E,0106,0612*0C

    0x34: Groups 3,5,6
    Group 3 (IMU):
        0x072E:
            UncompMag
            UncompAccel
            UncompGyro
            Pres
            Mag
            Accel
            AngularRate
    Group 5 (Attitude):
        0x0106:
            YawPitchRoll
            Quaternion
            YprU
    Group 6 (INS):
        0x0612:
            PosLLa
            VelNed
            PosU
            VelU

*/
static const uint8_t vn_pkt1_header[] { 0x34, 0x2E, 0x07, 0x06, 0x01, 0x12, 0x06 };
#define VN_PKT1_LENGTH 170 // includes header and CRC

struct PACKED VN_packet1 {
    float uncompMag[3];
    float uncompAccel[3];
    float uncompAngRate[3];
    float pressure;
    float mag[3];
    float accel[3];
    float gyro[3];
    float ypr[3];
    float quaternion[4];
    float yprU[3];
    double positionLLA[3];
    float velNED[3];
    float posU;
    float velU;
};

// check packet size for 4 groups
static_assert(sizeof(VN_packet1)+2+3*2+2 == VN_PKT1_LENGTH, "incorrect VN_packet1 length");

/*
  header for pre-configured 5Hz data
  assumes the following VN-300 config:
    $VNWRG,76,3,80,4E,0002,0010,20B8,0018*63

    0x4E: Groups 2,3,4,7
    Group 2 (Time):
        0x0002:
            TimeGps
    Group 3 (IMU):
        0x0010:
            Temp
    Group 4 (GPS1):
        0x20B8:
            NumSats
            Fix
            PosLLa
            VelNed
            DOP
    Group 7 (GPS2):
        0x0018:
            NumSats
            Fix
*/
static const uint8_t vn_pkt2_header[] { 0x4e, 0x02, 0x00, 0x10, 0x00, 0xb8, 0x20, 0x18, 0x00 };
#define VN_PKT2_LENGTH 92 // includes header and CRC

struct PACKED VN_packet2 {
    uint64_t timeGPS;
    float temp;
    uint8_t numGPS1Sats;
    uint8_t GPS1Fix;
    double GPS1posLLA[3];
    float GPS1velNED[3];
    float GPS1DOP[7];
    uint8_t numGPS2Sats;
    uint8_t GPS2Fix;
};

// check packet size for 4 groups
static_assert(sizeof(VN_packet2)+2+4*2+2 == VN_PKT2_LENGTH, "incorrect VN_packet2 length");

/*
  assumes the following VN-300 config:
    $VNWRG,75,3,80,14,073E,0004*66

  Alternate first packet for VN-100
    0x14: Groups 3, 5
        Group 3 (IMU):
            0x073E:
                UncompMag
                UncompAccel
                UncompGyro
                Temp
                Pres
                Mag
                Accel
                Gyro
        Group 5 (Attitude):
            0x0004:
                Quaternion
*/
static const uint8_t vn_100_pkt1_header[] { 0x14, 0x3E, 0x07, 0x04, 0x00 };
#define VN_100_PKT1_LENGTH 104 // includes header and CRC

struct PACKED VN_100_packet1 {
    float uncompMag[3];
    float uncompAccel[3];
    float uncompAngRate[3];
    float temp;
    float pressure;
    float mag[3];
    float accel[3];
    float gyro[3];
    float quaternion[4];
};

static_assert(sizeof(VN_100_packet1)+2+2*2+2 == VN_100_PKT1_LENGTH, "incorrect VN_100_packet1 length");

// constructor
AP_ExternalAHRS_VectorNav::AP_ExternalAHRS_VectorNav(AP_ExternalAHRS *_frontend,
                                                     AP_ExternalAHRS::state_t &_state) :
    AP_ExternalAHRS_backend(_frontend, _state)
{
    auto &sm = AP::serialmanager();
    uart = sm.find_serial(AP_SerialManager::SerialProtocol_AHRS, 0);
    if (!uart) {
        GCS_SEND_TEXT(MAV_SEVERITY_INFO, "ExternalAHRS no UART");
        return;
    }
    baudrate = sm.find_baudrate(AP_SerialManager::SerialProtocol_AHRS, 0);
    port_num = sm.find_portnum(AP_SerialManager::SerialProtocol_AHRS, 0);

    bufsize = MAX(MAX(VN_PKT1_LENGTH, VN_PKT2_LENGTH), VN_100_PKT1_LENGTH);
    pktbuf = new uint8_t[bufsize];
    last_pkt1 = new VN_packet1;
    last_pkt2 = new VN_packet2;

    if (!pktbuf || !last_pkt1 || !last_pkt2) {
        AP_BoardConfig::allocation_error("ExternalAHRS");
    }

    if (!hal.scheduler->thread_create(FUNCTOR_BIND_MEMBER(&AP_ExternalAHRS_VectorNav::update_thread, void), "AHRS", 2048, AP_HAL::Scheduler::PRIORITY_SPI, 0)) {
        AP_HAL::panic("Failed to start ExternalAHRS update thread");
    }
    GCS_SEND_TEXT(MAV_SEVERITY_INFO, "ExternalAHRS initialised");
}

/*
  check the UART for more data
  returns true if the function should be called again straight away
 */
#define SYNC_BYTE 0xFA
bool AP_ExternalAHRS_VectorNav::check_uart()
{
    if (!setup_complete) {
        return false;
    }
    WITH_SEMAPHORE(state.sem);
    uint32_t n = uart->available();
    if (n == 0) {
        return false;
    }
    if (pktoffset < bufsize) {
        ssize_t nread = uart->read(&pktbuf[pktoffset], MIN(n, unsigned(bufsize-pktoffset)));
        if (nread <= 0) {
            return false;
        }
        pktoffset += nread;
    }

    bool match_header1 = false;
    bool match_header2 = false;
    bool match_header3 = false;

    if (pktbuf[0] != SYNC_BYTE) {
        goto reset;
    }

    if (type == TYPE::VN_300) {
        match_header1 = (0 == memcmp(&pktbuf[1], vn_pkt1_header, MIN(sizeof(vn_pkt1_header), unsigned(pktoffset-1))));
        match_header2 = (0 == memcmp(&pktbuf[1], vn_pkt2_header, MIN(sizeof(vn_pkt2_header), unsigned(pktoffset-1))));
    } else {
        match_header3 = (0 == memcmp(&pktbuf[1], vn_100_pkt1_header, MIN(sizeof(vn_100_pkt1_header), unsigned(pktoffset-1))));
    }
    if (!match_header1 && !match_header2 && !match_header3) {
        goto reset;
    }

    if (match_header1 && pktoffset >= VN_PKT1_LENGTH) {
        uint16_t crc = crc16_ccitt(&pktbuf[1], VN_PKT1_LENGTH-1, 0);
        if (crc == 0) {
            // got pkt1
            process_packet1(&pktbuf[sizeof(vn_pkt1_header)+1]);
            memmove(&pktbuf[0], &pktbuf[VN_PKT1_LENGTH], pktoffset-VN_PKT1_LENGTH);
            pktoffset -= VN_PKT1_LENGTH;
        } else {
            goto reset;
        }
    } else if (match_header2 && pktoffset >= VN_PKT2_LENGTH) {
        uint16_t crc = crc16_ccitt(&pktbuf[1], VN_PKT2_LENGTH-1, 0);
        if (crc == 0) {
            // got pkt2
            process_packet2(&pktbuf[sizeof(vn_pkt2_header)+1]);
            memmove(&pktbuf[0], &pktbuf[VN_PKT2_LENGTH], pktoffset-VN_PKT2_LENGTH);
            pktoffset -= VN_PKT2_LENGTH;
        } else {
            goto reset;
        }
    } else if (match_header3 && pktoffset >= VN_100_PKT1_LENGTH) {
        uint16_t crc = crc16_ccitt(&pktbuf[1], VN_100_PKT1_LENGTH-1, 0);
        if (crc == 0) {
            // got VN-100 pkt1
            process_packet_VN_100(&pktbuf[sizeof(vn_100_pkt1_header)+1]);
            memmove(&pktbuf[0], &pktbuf[VN_100_PKT1_LENGTH], pktoffset-VN_100_PKT1_LENGTH);
            pktoffset -= VN_100_PKT1_LENGTH;
        } else {
            goto reset;
        }
    }
    return true;

reset:
    uint8_t *p = (uint8_t *)memchr(&pktbuf[1], SYNC_BYTE, pktoffset-1);
    if (p) {
        uint8_t newlen = pktoffset - (p - pktbuf);
        memmove(&pktbuf[0], p, newlen);
        pktoffset = newlen;
    } else {
        pktoffset = 0;
    }
    return true;
}

// Send command to read given register number and wait for response
// Only run from thread! This blocks until a response is received
#define READ_REQUEST_RETRY_MS 500
void AP_ExternalAHRS_VectorNav::wait_register_responce(const uint8_t register_num)
{
    nmea.register_number = register_num;

    uint32_t request_sent = 0;
    while (true) {
        hal.scheduler->delay(1);

        const uint32_t now = AP_HAL::millis();
        if (now - request_sent > READ_REQUEST_RETRY_MS) {
            // Send request to read
            nmea_printf(uart, "$%s%u", "VNRRG,", nmea.register_number);
            request_sent = now;
        }

        int16_t nbytes = uart->available();
        while (nbytes-- > 0) {
            char c = uart->read();
            if (decode(c)) {
                return;
            }
        }
    }
}

// add a single character to the buffer and attempt to decode
// returns true if a complete sentence was successfully decoded
bool AP_ExternalAHRS_VectorNav::decode(char c)
{
    switch (c) {
    case ',':
        // end of a term, add to checksum
        nmea.checksum ^= c;
        FALLTHROUGH;
    case '\r':
    case '\n':
    case '*':
    {
        if (nmea.sentence_done) {
            return false;
        }
        if (nmea.term_is_checksum) {
            nmea.sentence_done = true;
            uint8_t checksum = 16 * char_to_hex(nmea.term[0]) + char_to_hex(nmea.term[1]);
            return ((checksum == nmea.checksum) && nmea.sentence_valid);
        }

        // null terminate and decode latest term
        nmea.term[nmea.term_offset] = 0;
        if (nmea.sentence_valid) {
            nmea.sentence_valid = decode_latest_term();
        }

        // move onto next term
        nmea.term_number++;
        nmea.term_offset = 0;
        nmea.term_is_checksum = (c == '*');
        return false;
    }

    case '$': // sentence begin
        nmea.sentence_valid = true;
        nmea.term_number = 0;
        nmea.term_offset = 0;
        nmea.checksum = 0;
        nmea.term_is_checksum = false;
        nmea.sentence_done = false;
        return false;
    }

    // ordinary characters are added to term
    if (nmea.term_offset < sizeof(nmea.term) - 1) {
        nmea.term[nmea.term_offset++] = c;
    }
    if (!nmea.term_is_checksum) {
        nmea.checksum ^= c;
    }

    return false;
}

// decode the most recently consumed term
// returns true if new sentence has just passed checksum test and is validated
bool AP_ExternalAHRS_VectorNav::decode_latest_term()
{
    switch (nmea.term_number) {
        case 0:
            if (strcmp(nmea.term, "VNRRG") != 0) {
                return false;
            }
            break;

        case 1:
            if (nmea.register_number != strtoul(nmea.term, nullptr, 10)) {
                return false;
            }
            break;

        case 2:
            strncpy(model_name, nmea.term, sizeof(model_name));
            break;

        default:
            return false;
    }
    return true;
}

void AP_ExternalAHRS_VectorNav::update_thread()
{
    // Open port in the thread
    uart->begin(baudrate, 1024, 512);

    // Reset and wait for module to reboot
    // VN_100 takes 1.25 seconds
    //nmea_printf(uart, "$VNRST");
    //hal.scheduler->delay(3000);

    // Stop NMEA Async Outputs (this UART only)
    nmea_printf(uart, "$VNWRG,6,0");

    // Detect version
    // Read Model Number Register, ID 1
    wait_register_responce(1);

    // Setup for messages respective model types (on both UARTs)
    if (strncmp(model_name, "VN-100", 6) == 0) {
        // VN-100
        type = TYPE::VN_100;

        // This assumes unit is still configured at its default rate of 800hz
        nmea_printf(uart, "$VNWRG,75,3,%u,14,073E,0004", unsigned(800/get_rate()));

    } else {
        // Default to Setup for VN-300 series
        // This assumes unit is still configured at its default rate of 400hz
        nmea_printf(uart, "$VNWRG,75,3,%u,34,072E,0106,0612", unsigned(400/get_rate()));
        nmea_printf(uart, "$VNWRG,76,3,80,4E,0002,0010,20B8,0018");
    }

    setup_complete = true;
    while (true) {
        if (!check_uart()) {
            hal.scheduler->delay(1);
        }
    }
}

const char* AP_ExternalAHRS_VectorNav::get_name() const
{
    if (setup_complete) {
        return model_name;
    }
    return nullptr;
}

/*
  process packet type 1
 */
void AP_ExternalAHRS_VectorNav::process_packet1(const uint8_t *b)
{
    const struct VN_packet1 &pkt1 = *(struct VN_packet1 *)b;
    const struct VN_packet2 &pkt2 = *last_pkt2;

    last_pkt1_ms = AP_HAL::millis();
    *last_pkt1 = pkt1;

    const bool use_uncomp = option_is_set(AP_ExternalAHRS::OPTIONS::VN_UNCOMP_IMU);

    {
        WITH_SEMAPHORE(state.sem);
        if (use_uncomp) {
            state.accel = Vector3f{pkt1.uncompAccel[0], pkt1.uncompAccel[1], pkt1.uncompAccel[2]};
            state.gyro = Vector3f{pkt1.uncompAngRate[0], pkt1.uncompAngRate[1], pkt1.uncompAngRate[2]};
        } else {
            state.accel = Vector3f{pkt1.accel[0], pkt1.accel[1], pkt1.accel[2]};
            state.gyro = Vector3f{pkt1.gyro[0], pkt1.gyro[1], pkt1.gyro[2]};
        }

        state.quat = Quaternion{pkt1.quaternion[3], pkt1.quaternion[0], pkt1.quaternion[1], pkt1.quaternion[2]};
        state.have_quaternion = true;

        state.velocity = Vector3f{pkt1.velNED[0], pkt1.velNED[1], pkt1.velNED[2]};
        state.have_velocity = true;

        state.location = Location{int32_t(pkt1.positionLLA[0] * 1.0e7),
                                  int32_t(pkt1.positionLLA[1] * 1.0e7),
                                  int32_t(pkt1.positionLLA[2] * 1.0e2),
                                  Location::AltFrame::ABSOLUTE};
        state.have_location = true;
    }

#if AP_BARO_EXTERNALAHRS_ENABLED
    {
        AP_ExternalAHRS::baro_data_message_t baro;
        baro.instance = 0;
        baro.pressure_pa = pkt1.pressure*1e3;
        baro.temperature = pkt2.temp;

        AP::baro().handle_external(baro);
    }
#endif

#if AP_COMPASS_EXTERNALAHRS_ENABLED
    {
        AP_ExternalAHRS::mag_data_message_t mag;
        mag.field = Vector3f{pkt1.mag[0], pkt1.mag[1], pkt1.mag[2]};
        mag.field *= 1000; // to mGauss

        AP::compass().handle_external(mag);
    }
#endif

    {
        AP_ExternalAHRS::ins_data_message_t ins;

        ins.accel = state.accel;
        ins.gyro = state.gyro;
        ins.temperature = pkt2.temp;

        AP::ins().handle_external(ins);
    }


    // @LoggerMessage: EAH1
    // @Description: External AHRS data
    // @Field: TimeUS: Time since system startup
    // @Field: Roll: euler roll
    // @Field: Pitch: euler pitch
    // @Field: Yaw: euler yaw
    // @Field: VN: velocity north
    // @Field: VE: velocity east
    // @Field: VD: velocity down
    // @Field: Lat: latitude
    // @Field: Lon: longitude
    // @Field: Alt: altitude AMSL
    // @Field: UXY: uncertainty in XY position
    // @Field: UV: uncertainty in velocity
    // @Field: UR: uncertainty in roll
    // @Field: UP: uncertainty in pitch
    // @Field: UY: uncertainty in yaw

    AP::logger().WriteStreaming("EAH1", "TimeUS,Roll,Pitch,Yaw,VN,VE,VD,Lat,Lon,Alt,UXY,UV,UR,UP,UY",
                       "sdddnnnDUmmnddd", "F000000GG000000",
                       "QffffffLLffffff",
                       AP_HAL::micros64(),
                       pkt1.ypr[2], pkt1.ypr[1], pkt1.ypr[0],
                       pkt1.velNED[0], pkt1.velNED[1], pkt1.velNED[2],
                       int32_t(pkt1.positionLLA[0]*1.0e7), int32_t(pkt1.positionLLA[1]*1.0e7),
                       float(pkt1.positionLLA[2]),
                       pkt1.posU, pkt1.velU,
                       pkt1.yprU[2], pkt1.yprU[1], pkt1.yprU[0]);
}

/*
  process packet type 2
 */
void AP_ExternalAHRS_VectorNav::process_packet2(const uint8_t *b)
{
    const struct VN_packet2 &pkt2 = *(struct VN_packet2 *)b;
    const struct VN_packet1 &pkt1 = *last_pkt1;

    last_pkt2_ms = AP_HAL::millis();
    *last_pkt2 = pkt2;

    AP_ExternalAHRS::gps_data_message_t gps;

    // get ToW in milliseconds
    gps.gps_week = pkt2.timeGPS / (AP_MSEC_PER_WEEK * 1000000ULL);
    gps.ms_tow = (pkt2.timeGPS / 1000000ULL) % (60*60*24*7*1000ULL);
    gps.fix_type = pkt2.GPS1Fix;
    gps.satellites_in_view = pkt2.numGPS1Sats;

    gps.horizontal_pos_accuracy = pkt1.posU;
    gps.vertical_pos_accuracy = pkt1.posU;
    gps.horizontal_vel_accuracy = pkt1.velU;

    gps.hdop = pkt2.GPS1DOP[4];
    gps.vdop = pkt2.GPS1DOP[3];

    gps.latitude = pkt2.GPS1posLLA[0] * 1.0e7;
    gps.longitude = pkt2.GPS1posLLA[1] * 1.0e7;
    gps.msl_altitude = pkt2.GPS1posLLA[2] * 1.0e2;

    gps.ned_vel_north = pkt2.GPS1velNED[0];
    gps.ned_vel_east = pkt2.GPS1velNED[1];
    gps.ned_vel_down = pkt2.GPS1velNED[2];

    if (gps.fix_type >= 3 && !state.have_origin) {
        WITH_SEMAPHORE(state.sem);
        state.origin = Location{int32_t(pkt2.GPS1posLLA[0] * 1.0e7),
                                int32_t(pkt2.GPS1posLLA[1] * 1.0e7),
                                int32_t(pkt2.GPS1posLLA[2] * 1.0e2),
                                Location::AltFrame::ABSOLUTE};
        state.have_origin = true;
    }
    uint8_t instance;
    if (AP::gps().get_first_external_instance(instance)) {
        AP::gps().handle_external(gps, instance);
    }
}

/*
  process VN-100 packet type 1
 */
void AP_ExternalAHRS_VectorNav::process_packet_VN_100(const uint8_t *b)
{
    const struct VN_100_packet1 &pkt = *(struct VN_100_packet1 *)b;

    last_pkt1_ms = AP_HAL::millis();

    const bool use_uncomp = option_is_set(AP_ExternalAHRS::OPTIONS::VN_UNCOMP_IMU);

    {
        WITH_SEMAPHORE(state.sem);
        if (use_uncomp) {
            state.accel = Vector3f{pkt.uncompAccel[0], pkt.uncompAccel[1], pkt.uncompAccel[2]};
            state.gyro = Vector3f{pkt.uncompAngRate[0], pkt.uncompAngRate[1], pkt.uncompAngRate[2]};
        } else {
            state.accel = Vector3f{pkt.accel[0], pkt.accel[1], pkt.accel[2]};
            state.gyro = Vector3f{pkt.gyro[0], pkt.gyro[1], pkt.gyro[2]};
        }

        state.quat = Quaternion{pkt.quaternion[3], pkt.quaternion[0], pkt.quaternion[1], pkt.quaternion[2]};
        state.have_quaternion = true;
    }

#if AP_BARO_EXTERNALAHRS_ENABLED
    {
        AP_ExternalAHRS::baro_data_message_t baro;
        baro.instance = 0;
        baro.pressure_pa = pkt.pressure*1e3;
        baro.temperature = pkt.temp;

        AP::baro().handle_external(baro);
    }
#endif

#if AP_COMPASS_EXTERNALAHRS_ENABLED
    {
        AP_ExternalAHRS::mag_data_message_t mag;
        if (use_uncomp) {
            mag.field = Vector3f{pkt.uncompMag[0], pkt.uncompMag[1], pkt.uncompMag[2]};
        } else {
            mag.field = Vector3f{pkt.mag[0], pkt.mag[1], pkt.mag[2]};
        }
        mag.field *= 1000; // to mGauss

        AP::compass().handle_external(mag);
    }
#endif

    {
        AP_ExternalAHRS::ins_data_message_t ins;

        ins.accel = state.accel;
        ins.gyro = state.gyro;
        ins.temperature = pkt.temp;

        AP::ins().handle_external(ins);
    }

    // @LoggerMessage: EAH3
    // @Description: External AHRS data
    // @Field: TimeUS: Time since system startup
    // @Field: Temp: Temprature
    // @Field: Pres: Pressure
    // @Field: MX: Magnetic feild X-axis
    // @Field: MY: Magnetic feild Y-axis
    // @Field: MZ: Magnetic feild Z-axis
    // @Field: AX: Acceleration X-axis
    // @Field: AY: Acceleration Y-axis
    // @Field: AZ: Acceleration Z-axis
    // @Field: GX: Rotation rate X-axis
    // @Field: GY: Rotation rate Y-axis
    // @Field: GZ: Rotation rate Z-axis
    // @Field: Q1: Attitude quaternion 1
    // @Field: Q2: Attitude quaternion 2
    // @Field: Q3: Attitude quaternion 3
    // @Field: Q4: Attitude quaternion 4

    AP::logger().WriteStreaming("EAH3", "TimeUS,Temp,Pres,MX,MY,MZ,AX,AY,AZ,GX,GY,GZ,Q1,Q2,Q3,Q4",
                       "sdPGGGoooEEE----", "F000000000000000",
                       "Qfffffffffffffff",
                       AP_HAL::micros64(),
                       pkt.temp, pkt.pressure*1e3,
                       use_uncomp ? pkt.uncompMag[0] : pkt.mag[0],
                       use_uncomp ? pkt.uncompMag[1] : pkt.mag[1], 
                       use_uncomp ? pkt.uncompMag[2] : pkt.mag[2],
                       state.accel[0], state.accel[1], state.accel[2],
                       state.gyro[0], state.gyro[1], state.gyro[2],
                       state.quat[0], state.quat[1], state.quat[2], state.quat[3]);

}


// get serial port number for the uart
int8_t AP_ExternalAHRS_VectorNav::get_port(void) const
{
    if (!uart) {
        return -1;
    }
    return port_num;
};

// accessors for AP_AHRS
bool AP_ExternalAHRS_VectorNav::healthy(void) const
{
    const uint32_t now = AP_HAL::millis();
    if (type == TYPE::VN_100) {
        return (now - last_pkt1_ms < 40);
    }
    return (now - last_pkt1_ms < 40 && now - last_pkt2_ms < 500);
}

bool AP_ExternalAHRS_VectorNav::initialised(void) const
{
    if (!setup_complete) {
        return false;
    }
    if (type == TYPE::VN_100) {
        return last_pkt1_ms != 0;
    }
    return last_pkt1_ms != 0 && last_pkt2_ms != 0;
}

bool AP_ExternalAHRS_VectorNav::pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const
{
    if (!setup_complete) {
        hal.util->snprintf(failure_msg, failure_msg_len, "VectorNav setup failed");
        return false;
    }
    if (!healthy()) {
        hal.util->snprintf(failure_msg, failure_msg_len, "VectorNav unhealthy");
        return false;
    }
    if (type == TYPE::VN_300) {
        if (last_pkt2->GPS1Fix < 3) {
            hal.util->snprintf(failure_msg, failure_msg_len, "VectorNav no GPS1 lock");
            return false;
        }
        if (last_pkt2->GPS2Fix < 3) {
            hal.util->snprintf(failure_msg, failure_msg_len, "VectorNav no GPS2 lock");
            return false;
        }
    }
    return true;
}

/*
  get filter status. We don't know the meaning of the status bits yet,
  so assume all OK if we have GPS lock
 */
void AP_ExternalAHRS_VectorNav::get_filter_status(nav_filter_status &status) const
{
    memset(&status, 0, sizeof(status));
    if (type == TYPE::VN_300) {
        if (last_pkt1 && last_pkt2) {
            status.flags.initalized = true;
        }
        if (healthy() && last_pkt2) {
            status.flags.attitude = true;
            status.flags.vert_vel = true;
            status.flags.vert_pos = true;

            const struct VN_packet2 &pkt2 = *last_pkt2;
            if (pkt2.GPS1Fix >= 3) {
                status.flags.horiz_vel = true;
                status.flags.horiz_pos_rel = true;
                status.flags.horiz_pos_abs = true;
                status.flags.pred_horiz_pos_rel = true;
                status.flags.pred_horiz_pos_abs = true;
                status.flags.using_gps = true;
            }
        }
    } else {
        status.flags.initalized = initialised();
        if (healthy()) {
            status.flags.attitude = true;
        }
    }
}

// send an EKF_STATUS message to GCS
void AP_ExternalAHRS_VectorNav::send_status_report(GCS_MAVLINK &link) const
{
    if (!last_pkt1) {
        return;
    }
    // prepare flags
    uint16_t flags = 0;
    nav_filter_status filterStatus;
    get_filter_status(filterStatus);
    if (filterStatus.flags.attitude) {
        flags |= EKF_ATTITUDE;
    }
    if (filterStatus.flags.horiz_vel) {
        flags |= EKF_VELOCITY_HORIZ;
    }
    if (filterStatus.flags.vert_vel) {
        flags |= EKF_VELOCITY_VERT;
    }
    if (filterStatus.flags.horiz_pos_rel) {
        flags |= EKF_POS_HORIZ_REL;
    }
    if (filterStatus.flags.horiz_pos_abs) {
        flags |= EKF_POS_HORIZ_ABS;
    }
    if (filterStatus.flags.vert_pos) {
        flags |= EKF_POS_VERT_ABS;
    }
    if (filterStatus.flags.terrain_alt) {
        flags |= EKF_POS_VERT_AGL;
    }
    if (filterStatus.flags.const_pos_mode) {
        flags |= EKF_CONST_POS_MODE;
    }
    if (filterStatus.flags.pred_horiz_pos_rel) {
        flags |= EKF_PRED_POS_HORIZ_REL;
    }
    if (filterStatus.flags.pred_horiz_pos_abs) {
        flags |= EKF_PRED_POS_HORIZ_ABS;
    }
    if (!filterStatus.flags.initalized) {
        flags |= EKF_UNINITIALIZED;
    }

    // send message
    const struct VN_packet1 &pkt1 = *(struct VN_packet1 *)last_pkt1;
    const float vel_gate = 5;
    const float pos_gate = 5;
    const float hgt_gate = 5;
    const float mag_var = 0;
    mavlink_msg_ekf_status_report_send(link.get_chan(), flags,
                                       pkt1.velU/vel_gate, pkt1.posU/pos_gate, pkt1.posU/hgt_gate,
                                       mag_var, 0, 0);
}

#endif  // AP_EXTERNAL_AHRS_VECTORNAV_ENABLED