#include "AP_Mount_Backend.h"
#if HAL_MOUNT_ENABLED
#include <AP_AHRS/AP_AHRS.h>

extern const AP_HAL::HAL& hal;

#define AP_MOUNT_UPDATE_DT 0.02     // update rate in seconds.  update() should be called at this rate

// set_angle_targets - sets angle targets in degrees
void AP_Mount_Backend::set_angle_targets(float roll, float tilt, float pan)
{
    // set angle targets
    _angle_ef_target_rad.x = radians(roll);
    _angle_ef_target_rad.y = radians(tilt);
    _angle_ef_target_rad.z = radians(pan);

    // set the mode to mavlink targeting
    _frontend.set_mode(_instance, MAV_MOUNT_MODE_MAVLINK_TARGETING);
}

// set_roi_target - sets target location that mount should attempt to point towards
void AP_Mount_Backend::set_roi_target(const struct Location &target_loc)
{
    // set the target gps location
    _state._roi_target = target_loc;
    _state._roi_target_set = true;

    // set the mode to GPS tracking mode
    _frontend.set_mode(_instance, MAV_MOUNT_MODE_GPS_POINT);
}

// set_sys_target - sets system that mount should attempt to point towards
void AP_Mount_Backend::set_target_sysid(uint8_t sysid)
{
    _state._target_sysid = sysid;

    // set the mode to sysid tracking mode
    _frontend.set_mode(_instance, MAV_MOUNT_MODE_SYSID_TARGET);
}

// process MOUNT_CONFIGURE messages received from GCS. deprecated.
void AP_Mount_Backend::handle_mount_configure(const mavlink_mount_configure_t &packet)
{
    set_mode((MAV_MOUNT_MODE)packet.mount_mode);
    _state._stab_roll = packet.stab_roll;
    _state._stab_tilt = packet.stab_pitch;
    _state._stab_pan = packet.stab_yaw;
}

// process MOUNT_CONTROL messages received from GCS. deprecated.
void AP_Mount_Backend::handle_mount_control(const mavlink_mount_control_t &packet)
{
    control((int32_t)packet.input_a, (int32_t)packet.input_b, (int32_t)packet.input_c, _state._mode);
}

void AP_Mount_Backend::control(int32_t pitch_or_lat, int32_t roll_or_lon, int32_t yaw_or_alt, MAV_MOUNT_MODE mount_mode)
{
    _frontend.set_mode(_instance, mount_mode);

    // interpret message fields based on mode
    switch (_frontend.get_mode(_instance)) {
        case MAV_MOUNT_MODE_RETRACT:
        case MAV_MOUNT_MODE_NEUTRAL:
            // do nothing with request if mount is retracted or in neutral position
            break;

        // set earth frame target angles from mavlink message
        case MAV_MOUNT_MODE_MAVLINK_TARGETING:
            set_angle_targets(roll_or_lon*0.01f, pitch_or_lat*0.01f, yaw_or_alt*0.01f);
            break;

        // Load neutral position and start RC Roll,Pitch,Yaw control with stabilization
        case MAV_MOUNT_MODE_RC_TARGETING:
            // do nothing if pilot is controlling the roll, pitch and yaw
            break;

        // set lat, lon, alt position targets from mavlink message

        case MAV_MOUNT_MODE_GPS_POINT: {
            const Location target_location{
                pitch_or_lat,
                roll_or_lon,
                yaw_or_alt,
                Location::AltFrame::ABOVE_HOME
            };
            set_roi_target(target_location);
            break;
        }

        case MAV_MOUNT_MODE_HOME_LOCATION: {
            // set the target gps location
            _state._roi_target = AP::ahrs().get_home();
            _state._roi_target_set = true;
            break;
        }

        default:
            // do nothing
            break;
    }
}

// handle a GLOBAL_POSITION_INT message
bool AP_Mount_Backend::handle_global_position_int(uint8_t msg_sysid, const mavlink_global_position_int_t &packet)
{
    if (_state._target_sysid != msg_sysid) {
        return false;
    }

    _state._target_sysid_location.lat = packet.lat;
    _state._target_sysid_location.lng = packet.lon;
    // global_position_int.alt is *UP*, so is location.
    _state._target_sysid_location.set_alt_cm(packet.alt*0.1, Location::AltFrame::ABSOLUTE);
    _state._target_sysid_location_set = true;

    return true;
}

// update rate and angle targets from RC input
// current angle target (in radians) should be provided in angle_rad target
// rate and angle targets are returned in rate_rads and angle_rad arguments
// angle min and max are in centi-degrees
void AP_Mount_Backend::update_rate_and_angle_from_rc(const RC_Channel *chan, float &rate_rads, float &angle_rad, float angle_min_cd, float angle_max_cd) const
{
    if ((chan == nullptr) || (chan->get_radio_in() == 0)) {
        rate_rads = 0;
        return;
    }
    rate_rads = chan->norm_input_dz() * radians(_frontend._rc_rate_max);
    angle_rad = constrain_float(angle_rad + (rate_rads * AP_MOUNT_UPDATE_DT), radians(angle_min_cd*0.01f), radians(angle_max_cd*0.01f));
}

// update_targets_from_rc - updates angle targets using input from receiver
void AP_Mount_Backend::update_targets_from_rc()
{
    const RC_Channel *roll_ch = rc().channel(_state._roll_rc_in - 1);
    const RC_Channel *tilt_ch = rc().channel(_state._tilt_rc_in - 1);
    const RC_Channel *pan_ch = rc().channel(_state._pan_rc_in - 1);

    // if joystick_speed is defined then pilot input defines a rate of change of the angle
    if (_frontend._rc_rate_max > 0) {
        // allow pilot position input to come directly from an RC_Channel
        update_rate_and_angle_from_rc(roll_ch, _rate_target_rads.x, _angle_ef_target_rad.x, _state._roll_angle_min, _state._roll_angle_max);
        update_rate_and_angle_from_rc(tilt_ch, _rate_target_rads.y, _angle_ef_target_rad.y, _state._tilt_angle_min, _state._tilt_angle_max);
        update_rate_and_angle_from_rc(pan_ch, _rate_target_rads.z, _angle_ef_target_rad.z, _state._pan_angle_min, _state._pan_angle_max);
        _rate_target_rads_valid = true;
    } else {
        // allow pilot rate input to come directly from an RC_Channel
        if ((roll_ch != nullptr) && (roll_ch->get_radio_in() != 0)) {
            _angle_ef_target_rad.x = angle_input_rad(roll_ch, _state._roll_angle_min, _state._roll_angle_max);
        }
        if ((tilt_ch != nullptr) && (tilt_ch->get_radio_in() != 0)) {
            _angle_ef_target_rad.y = angle_input_rad(tilt_ch, _state._tilt_angle_min, _state._tilt_angle_max);
        }
        if ((pan_ch != nullptr) && (pan_ch->get_radio_in() != 0)) {
            _angle_ef_target_rad.z = angle_input_rad(pan_ch, _state._pan_angle_min, _state._pan_angle_max);
        }
        // not using rate input
        _rate_target_rads_valid = false;
    }
}

// returns the angle (radians) that the RC_Channel input is receiving
float AP_Mount_Backend::angle_input_rad(const RC_Channel* rc, int16_t angle_min, int16_t angle_max)
{
    return radians(((rc->norm_input_ignore_trim() + 1.0f) * 0.5f * (angle_max - angle_min) + angle_min)*0.01f);
}

bool AP_Mount_Backend::calc_angle_to_roi_target(Vector3f& angles_to_target_rad, bool calc_tilt, bool calc_pan, bool relative_pan) const
{
    if (!_state._roi_target_set) {
        return false;
    }
    return calc_angle_to_location(_state._roi_target, angles_to_target_rad, calc_tilt, calc_pan, relative_pan);
}

bool AP_Mount_Backend::calc_angle_to_sysid_target(Vector3f& angles_to_target_rad, bool calc_tilt, bool calc_pan, bool relative_pan) const
{
    if (!_state._target_sysid_location_set) {
        return false;
    }
    if (!_state._target_sysid) {
        return false;
    }
    return calc_angle_to_location(_state._target_sysid_location, angles_to_target_rad, calc_tilt, calc_pan, relative_pan);
}

// calc_angle_to_location - calculates the earth-frame roll, tilt and pan angles (in radians) to point at the given target
bool AP_Mount_Backend::calc_angle_to_location(const struct Location &target, Vector3f& angles_to_target_rad, bool calc_tilt, bool calc_pan, bool relative_pan) const
{
    Location current_loc;
    if (!AP::ahrs().get_location(current_loc)) {
        return false;
    }
    const float GPS_vector_x = Location::diff_longitude(target.lng,current_loc.lng)*cosf(ToRad((current_loc.lat+target.lat)*0.00000005f))*0.01113195f;
    const float GPS_vector_y = (target.lat-current_loc.lat)*0.01113195f;
    int32_t target_alt_cm = 0;
    if (!target.get_alt_cm(Location::AltFrame::ABOVE_HOME, target_alt_cm)) {
        return false;
    }
    int32_t current_alt_cm = 0;
    if (!current_loc.get_alt_cm(Location::AltFrame::ABOVE_HOME, current_alt_cm)) {
        return false;
    }
    float GPS_vector_z = target_alt_cm - current_alt_cm;
    float target_distance = 100.0f*norm(GPS_vector_x, GPS_vector_y);      // Careful , centimeters here locally. Baro/alt is in cm, lat/lon is in meters.

    // initialise all angles to zero
    angles_to_target_rad.zero();

    // tilt calcs
    if (calc_tilt) {
        angles_to_target_rad.y = atan2f(GPS_vector_z, target_distance);
    }

    // pan calcs
    if (calc_pan) {
        // calc absolute heading and then convert to vehicle relative yaw
        angles_to_target_rad.z = atan2f(GPS_vector_x, GPS_vector_y);
        if (relative_pan) {
            angles_to_target_rad.z = wrap_PI(angles_to_target_rad.z - AP::ahrs().yaw);
        }
    }
    return true;
}

#endif // HAL_MOUNT_ENABLED