sim-modem/api/modem/gps/check.go

package gps

import (
	"fmt"
	"strconv"
	"strings"
)

type Status struct {
	GotResponses          bool `json:"gotResponses"`
	FoundSatelitesCount   int  `json:"foundSatelitesCount"`
	ActiveSatelitesCounte int  `json:"activeSatelitesCount"`
}

func (st Status) String() string {
	got := "false"
	if st.GotResponses {
		got = "true"
	}
	return "" +
		"GotResponses:          " + got + "\n" +
		"FoundSatelitesCount:   " + string(st.FoundSatelitesCount) + "\n" +
		"ActiveSatelitesCounte: " + string(st.ActiveSatelitesCounte) + "\n"
}

var StatusNil = Status{
	GotResponses:          false,
	FoundSatelitesCount:   0,
	ActiveSatelitesCounte: 0,
}

func (g *gps) CheckStatus() (Status, error) {
	// Provides more information about signal and possible problems using NMEA reports

	// Collect reports
	reports, err := g.collectNmeaReports(nmeaFlagsAll) // Now minimum
	if err != nil {
		return StatusNil, fmt.Errorf("collect nmea reports: %w", err)
	}

	// Annalise
	st := Status{}

checkLoop:
	for _, s := range reports {
		// Check for NMEA format
		if len(s) < 1 || s[0] != '$' {
			continue checkLoop
		}
		st.GotResponses = true

		g.logger.Println("NMEA check:", s)
		values := strings.Split(s, ",")
		if len(values[0]) != 6 {
			return StatusNil, fmt.Errorf("nmea invalid sentence: %s", s)
		}
		switch values[0][3:] { // Switch by content
		case "gsv":
			if len(values) < 17 {
				g.logger.Println("GSV too small values")
				continue checkLoop
			}
			c, err := strconv.Atoi(values[4])
			if err != nil {
				g.logger.Println("GSV too small values")
				continue checkLoop
			}
			st.FoundSatelitesCount += c
		}
	}

	return st, nil
}