// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
   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/>.
 */

//
//  u-blox UBX GPS driver for ArduPilot and ArduPilotMega.
//	Code by Michael Smith, Jordi Munoz and Jose Julio, DIYDrones.com
//
#include <stdint.h>

#include <AP_HAL.h>

#define UBLOX_DEBUGGING 0
#define UBLOX_FAKE_3DLOCK 0

extern const AP_HAL::HAL& hal;

#if UBLOX_DEBUGGING
 # define Debug(fmt, args ...)  do {hal.console->printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); hal.scheduler->delay(1); } while(0)
#else
 # define Debug(fmt, args ...)
#endif

#include "AP_GPS_UBLOX.h"

extern const AP_HAL::HAL& hal;

const prog_char AP_GPS_UBLOX::_ublox_set_binary[] PROGMEM = UBLOX_SET_BINARY;
const uint8_t AP_GPS_UBLOX::_ublox_set_binary_size = sizeof(AP_GPS_UBLOX::_ublox_set_binary);

// Public Methods //////////////////////////////////////////////////////////////

void
AP_GPS_UBLOX::init(AP_HAL::UARTDriver *s, enum GPS_Engine_Setting nav_setting)
{
	_port = s;

    // XXX it might make sense to send some CFG_MSG,CFG_NMEA messages to get the
    // right reporting configuration.

	Debug("uBlox nav_setting=%u\n", nav_setting);

    _port->flush();

    // configure the GPS for the messages we want
    _configure_gps();

    _nav_setting = nav_setting;
	_step = 0;
	_new_position = false;
	_new_speed = false;
}

/*
  send the next step of rate updates to the GPS. This reconfigures the
  GPS on the fly to have the right message rates. It needs to be
  careful to only send a message if there is sufficient buffer space
  available on the serial port to avoid it blocking the CPU
 */
void
AP_GPS_UBLOX::send_next_rate_update(void)
{
    if (_port->txspace() < (int16_t)(sizeof(struct ubx_header)+sizeof(struct ubx_cfg_nav_rate)+2)) {
        // not enough space - do it next time
        return;
    }

    //hal.console->printf_P(PSTR("next_rate: %u\n"), (unsigned)rate_update_step);

    switch (rate_update_step) {
    case 0:
        _configure_navigation_rate(200);
        break;
    case 1:
        _configure_message_rate(CLASS_NAV, MSG_POSLLH, 1);
        break;
    case 2:
        _configure_message_rate(CLASS_NAV, MSG_STATUS, 1);
        break;
    case 3:
        _configure_message_rate(CLASS_NAV, MSG_SOL, 1);
        break;
    case 4:
        _configure_message_rate(CLASS_NAV, MSG_VELNED, 1);
        break;
    }
    rate_update_step++;
    if (rate_update_step > 4) {
        need_rate_update = false;
        rate_update_step = 0;
    }
}


// Process bytes available from the stream
//
// The stream is assumed to contain only messages we recognise.  If it
// contains other messages, and those messages contain the preamble
// bytes, it is possible for this code to fail to synchronise to the
// stream immediately.  Without buffering the entire message and
// re-processing it from the top, this is unavoidable. The parser
// attempts to avoid this when possible.
//
bool
AP_GPS_UBLOX::read(void)
{
    uint8_t data;
    int16_t numc;
    bool parsed = false;

    if (need_rate_update) {
        send_next_rate_update();
    }

    numc = _port->available();
    for (int16_t i = 0; i < numc; i++) {        // Process bytes received

        // read the next byte
        data = _port->read();

	reset:
        switch(_step) {

        // Message preamble detection
        //
        // If we fail to match any of the expected bytes, we reset
        // the state machine and re-consider the failed byte as
        // the first byte of the preamble.  This improves our
        // chances of recovering from a mismatch and makes it less
        // likely that we will be fooled by the preamble appearing
        // as data in some other message.
        //
        case 1:
            if (PREAMBLE2 == data) {
                _step++;
                break;
            }
            _step = 0;
            Debug("reset %u", __LINE__);
        // FALLTHROUGH
        case 0:
            if(PREAMBLE1 == data)
                _step++;
            break;

        // Message header processing
        //
        // We sniff the class and message ID to decide whether we
        // are going to gather the message bytes or just discard
        // them.
        //
        // We always collect the length so that we can avoid being
        // fooled by preamble bytes in messages.
        //
        case 2:
            _step++;
            _class = data;
            _ck_b = _ck_a = data;                               // reset the checksum accumulators
            break;
        case 3:
            _step++;
            _ck_b += (_ck_a += data);                   // checksum byte
            _msg_id = data;
            break;
        case 4:
            _step++;
            _ck_b += (_ck_a += data);                   // checksum byte
            _payload_length = data;                             // payload length low byte
            break;
        case 5:
            _step++;
            _ck_b += (_ck_a += data);                   // checksum byte

            _payload_length += (uint16_t)(data<<8);
            if (_payload_length > 512) {
                Debug("large payload %u", (unsigned)_payload_length);
                // assume very large payloads are line noise
                _payload_length = 0;
                _step = 0;
				goto reset;
            }
            _payload_counter = 0;                               // prepare to receive payload
            break;

        // Receive message data
        //
        case 6:
            _ck_b += (_ck_a += data);                   // checksum byte
            if (_payload_counter < sizeof(_buffer)) {
                _buffer.bytes[_payload_counter] = data;
            }
            if (++_payload_counter == _payload_length)
                _step++;
            break;

        // Checksum and message processing
        //
        case 7:
            _step++;
            if (_ck_a != data) {
                Debug("bad cka %x should be %x", data, _ck_a);
                _step = 0;
				goto reset;
            }
            break;
        case 8:
            _step = 0;
            if (_ck_b != data) {
                Debug("bad ckb %x should be %x", data, _ck_b);
                break;                                                  // bad checksum
            }

            if (_parse_gps()) {
                parsed = true;
            }
        }
    }
    return parsed;
}

// Private Methods /////////////////////////////////////////////////////////////

bool
AP_GPS_UBLOX::_parse_gps(void)
{
    if (_class == CLASS_ACK) {
        Debug("ACK %u", (unsigned)_msg_id);
        return false;
    }

    if (_class == CLASS_CFG && _msg_id == MSG_CFG_NAV_SETTINGS) {
		Debug("Got engine settings %u\n", (unsigned)_buffer.nav_settings.dynModel);
        if (_nav_setting != GPS_ENGINE_NONE &&
            _buffer.nav_settings.dynModel != _nav_setting) {
            // we've received the current nav settings, change the engine
            // settings and send them back
            Debug("Changing engine setting from %u to %u\n",
                  (unsigned)_buffer.nav_settings.dynModel, (unsigned)_nav_setting);
            _buffer.nav_settings.dynModel = _nav_setting;
            _buffer.nav_settings.mask = 1; // only change dynamic model
            _send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS,
                          &_buffer.nav_settings,
                          sizeof(_buffer.nav_settings));
        }
        return false;
    }

    if (_class != CLASS_NAV) {
        Debug("Unexpected message 0x%02x 0x%02x", (unsigned)_class, (unsigned)_msg_id);
        if (++_disable_counter == 0) {
            // disable future sends of this message id, but
            // only do this every 256 messages, as some
            // message types can't be disabled and we don't
            // want to get into an ack war
            Debug("Disabling message 0x%02x 0x%02x", (unsigned)_class, (unsigned)_msg_id);
            _configure_message_rate(_class, _msg_id, 0);
        }
        return false;
    }

    switch (_msg_id) {
    case MSG_POSLLH:
        Debug("MSG_POSLLH next_fix=%u", next_fix);
        longitude       = _buffer.posllh.longitude;
        latitude        = _buffer.posllh.latitude;
        altitude_cm     = _buffer.posllh.altitude_msl / 10;
        fix             = next_fix;
        _new_position = true;
#if UBLOX_FAKE_3DLOCK
        longitude = 1491652300L;
        latitude  = -353632610L;
        altitude_cm = 58400;
#endif
        break;
    case MSG_STATUS:
        Debug("MSG_STATUS fix_status=%u fix_type=%u",
              _buffer.status.fix_status,
              _buffer.status.fix_type);
        if (_buffer.status.fix_status & NAV_STATUS_FIX_VALID) {
            if( _buffer.status.fix_type == AP_GPS_UBLOX::FIX_3D) {
                next_fix = GPS::FIX_3D;
            }else if (_buffer.status.fix_type == AP_GPS_UBLOX::FIX_2D) {
                next_fix = GPS::FIX_2D;
            }else{
                next_fix = GPS::FIX_NONE;
                fix = GPS::FIX_NONE;
            }
        }else{
            next_fix = GPS::FIX_NONE;
            fix = GPS::FIX_NONE;
        }
#if UBLOX_FAKE_3DLOCK
        fix = GPS::FIX_3D;
        next_fix = fix;
#endif
        break;
    case MSG_SOL:
        Debug("MSG_SOL fix_status=%u fix_type=%u",
              _buffer.solution.fix_status,
              _buffer.solution.fix_type);
        if (_buffer.solution.fix_status & NAV_STATUS_FIX_VALID) {
            if( _buffer.solution.fix_type == AP_GPS_UBLOX::FIX_3D) {
                next_fix = GPS::FIX_3D;
            }else if (_buffer.solution.fix_type == AP_GPS_UBLOX::FIX_2D) {
                next_fix = GPS::FIX_2D;
            }else{
                next_fix = GPS::FIX_NONE;
                fix = GPS::FIX_NONE;
            }
        }else{
            next_fix = GPS::FIX_NONE;
            fix = GPS::FIX_NONE;
        }
        num_sats        = _buffer.solution.satellites;
        hdop            = _buffer.solution.position_DOP;
        if (next_fix >= GPS::FIX_2D) {
            time_week_ms    = _buffer.solution.time;
            time_week       = _buffer.solution.week;
            _last_gps_time  = hal.scheduler->millis();
        }
#if UBLOX_FAKE_3DLOCK
        next_fix = fix;
        num_sats = 10;
        hdop = 200;
        time_week = 1721;
        time_week_ms = hal.scheduler->millis() + 3*60*60*1000 + 37000;
        _last_gps_time  = hal.scheduler->millis();
#endif
        break;
    case MSG_VELNED:
        Debug("MSG_VELNED");
        speed_3d_cm     = _buffer.velned.speed_3d;                              // cm/s
        ground_speed_cm = _buffer.velned.speed_2d;                         // cm/s
        ground_course_cd = _buffer.velned.heading_2d / 1000;       // Heading 2D deg * 100000 rescaled to deg * 100
        _have_raw_velocity = true;
        _vel_north  = _buffer.velned.ned_north;
        _vel_east   = _buffer.velned.ned_east;
        _vel_down   = _buffer.velned.ned_down;
        _new_speed = true;
        break;
    default:
        Debug("Unexpected NAV message 0x%02x", (unsigned)_msg_id);
        if (++_disable_counter == 0) {
            Debug("Disabling NAV message 0x%02x", (unsigned)_msg_id);
            _configure_message_rate(CLASS_NAV, _msg_id, 0);
        }
        return false;
    }

    // we only return true when we get new position and speed data
    // this ensures we don't use stale data
    if (_new_position && _new_speed) {
        _new_speed = _new_position = false;
		_fix_count++;
        uint32_t new_fix_time = hal.scheduler->millis();

        if (!need_rate_update && new_fix_time - _last_fix_time > 300 && _fix_count % 20 == 0) {
            // the GPS is running slow. It possibly browned out and
            // restarted with incorrect parameters. We will slowly
            // send out new parameters to fix it
            need_rate_update = true;
            rate_update_step = 0;
        }
        _last_fix_time = new_fix_time;

		if (_fix_count == 100) {
			// ask for nav settings every 20 seconds
			Debug("Asking for engine setting\n");
			_send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS, NULL, 0);
            _fix_count = 0;
		}
        return true;
    }
    return false;
}


// UBlox auto configuration

/*
 *  update checksum for a set of bytes
 */
void
AP_GPS_UBLOX::_update_checksum(uint8_t *data, uint8_t len, uint8_t &ck_a, uint8_t &ck_b)
{
    while (len--) {
        ck_a += *data;
        ck_b += ck_a;
        data++;
    }
}


/*
 *  send a ublox message
 */
void
AP_GPS_UBLOX::_send_message(uint8_t msg_class, uint8_t msg_id, void *msg, uint8_t size)
{
    struct ubx_header header;
    uint8_t ck_a=0, ck_b=0;
    header.preamble1 = PREAMBLE1;
    header.preamble2 = PREAMBLE2;
    header.msg_class = msg_class;
    header.msg_id    = msg_id;
    header.length    = size;

    _update_checksum((uint8_t *)&header.msg_class, sizeof(header)-2, ck_a, ck_b);
    _update_checksum((uint8_t *)msg, size, ck_a, ck_b);

    _port->write((const uint8_t *)&header, sizeof(header));
    _port->write((const uint8_t *)msg, size);
    _port->write((const uint8_t *)&ck_a, 1);
    _port->write((const uint8_t *)&ck_b, 1);
}


/*
 *  configure a UBlox GPS for the given message rate for a specific
 *  message class and msg_id
 */
void
AP_GPS_UBLOX::_configure_message_rate(uint8_t msg_class, uint8_t msg_id, uint8_t rate)
{
    struct ubx_cfg_msg_rate msg;
    msg.msg_class = msg_class;
    msg.msg_id    = msg_id;
    msg.rate          = rate;
    _send_message(CLASS_CFG, MSG_CFG_SET_RATE, &msg, sizeof(msg));
}

/*
 *  configure a UBlox GPS navigation solution rate of 200ms
 */
void
AP_GPS_UBLOX::_configure_navigation_rate(uint16_t rate_ms)
{
    struct ubx_cfg_nav_rate msg;
    msg.measure_rate_ms = rate_ms;
    msg.nav_rate        = 1;
    msg.timeref         = 0;     // UTC time
    _send_message(CLASS_CFG, MSG_CFG_RATE, &msg, sizeof(msg));
}

/*
 *  configure a UBlox GPS for the given message rate
 */
void
AP_GPS_UBLOX::_configure_gps(void)
{
    const unsigned baudrates[4] = {9600U, 19200U, 38400U, 57600U};

    // the GPS may be setup for a different baud rate. This ensures
    // it gets configured correctly
    for (uint8_t i=0; i<4; i++) {
        _port->begin(baudrates[i]);
        _write_progstr_block(_port, _ublox_set_binary, _ublox_set_binary_size);
        while (_port->tx_pending()) {
          hal.scheduler->delay(1);
        }
    }
    _port->begin(38400U);

    // start the process of updating the GPS rates
    need_rate_update = true;
    rate_update_step = 0;

    // ask for the current navigation settings
	Debug("Asking for engine setting\n");
    _send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS, NULL, 0);
}


/*
  detect a Ublox GPS. Adds one byte, and returns true if the stream
  matches a UBlox
 */
bool
AP_GPS_UBLOX::_detect(uint8_t data)
{
	static uint8_t payload_length, payload_counter;
	static uint8_t step;
	static uint8_t ck_a, ck_b;

reset:
	switch (step) {
        case 1:
            if (PREAMBLE2 == data) {
                step++;
                break;
            }
            step = 0;
        case 0:
            if (PREAMBLE1 == data)
                step++;
            break;
        case 2:
            step++;
            ck_b = ck_a = data;
            break;
        case 3:
            step++;
            ck_b += (ck_a += data);
            break;
        case 4:
            step++;
            ck_b += (ck_a += data);
            payload_length = data;
            break;
        case 5:
            step++;
            ck_b += (ck_a += data);
            payload_counter = 0;
            break;
        case 6:
            ck_b += (ck_a += data);
            if (++payload_counter == payload_length)
                step++;
            break;
        case 7:
            step++;
            if (ck_a != data) {
                step = 0;
				goto reset;
            }
            break;
        case 8:
            step = 0;
			if (ck_b == data) {
				// a valid UBlox packet
				return true;
			} else {
				goto reset;
			}
    }
    return false;
}