gpgsa.go

package nmea

import (
	"fmt"
	"strconv"
)

// Examples:
// $GPGSA,A,3,14,06,16,31,23,,,,,,,,1.66,1.42,0.84*0F

func NewGPGSA(m Message) *GPGSA {
	return &GPGSA{Message: m}
}

type GPGSA struct {
	Message

	Mode                   Mode
	FixStatus              FixStatus
	SatelliteUsedOnChannel [13]int // Note: index 0 not used (channel 1..12)
	PDOP, HDOP, VDOP       float64
}

func (m *GPGSA) parse() (err error) {
	if len(m.Fields) != 17 {
		return m.Error(fmt.Errorf("Incomplete GPGSA message, not enougth data fields (got: %d, wanted: %d)", len(m.Fields), 17))
	}

	if m.Mode, err = ParseMode(m.Fields[0]); err != nil {
		return m.Error(err)
	}

	if m.FixStatus, err = ParseFixStatus(m.Fields[1]); err != nil {
		return m.Error(err)
	}

	for k, v := range m.Fields[2:14] {
		m.SatelliteUsedOnChannel[k+1], _ = strconv.Atoi(v)
	}

	// data could be empty
	pdop, hdop, vdop := m.Fields[14], m.Fields[15], m.Fields[16]

	if len(pdop) > 0 {
		if m.PDOP, err = strconv.ParseFloat(pdop, 64); err != nil {
			return m.Error(err)
		}
	}

	if len(hdop) > 0 {
		if m.HDOP, err = strconv.ParseFloat(hdop, 64); err != nil {
			return m.Error(err)
		}
	}

	if len(vdop) > 0 {
		if m.VDOP, err = strconv.ParseFloat(vdop, 64); err != nil {
			return m.Error(err)
		}
	}

	return nil
}

const (
	_ = iota
	FixStatusNoFix
	FixStatus2D
	FixStatus3D
)

type FixStatus int

func (s FixStatus) String() string {
	switch s {
	case FixStatusNoFix:
		return "No fix"
	case FixStatus2D:
		return "2D fix"
	case FixStatus3D:
		return "3D fix"
	default:
		return "unknow"
	}
}

func ParseFixStatus(raw string) (fs FixStatus, err error) {
	i, err := strconv.ParseInt(raw, 10, 0)
	if err != nil {
		return
	}

	fs = FixStatus(i)
	switch fs {
	case FixStatusNoFix, FixStatus2D, FixStatus3D:
	default:
		err = fmt.Errorf("unknow value (got: %d)", i)
	}
	return
}

const (
	ModeManual Mode = "M"
	ModeAuto   Mode = "A"
)

type Mode string

func (m Mode) String() string {
	return string(m)
}

func ParseMode(raw string) (m Mode, err error) {
	m = Mode(raw)
	switch m {
	case ModeManual, ModeAuto:
	default:
		err = fmt.Errorf("unknow value (got: %s)", m)
	}
	return
}