Get Position from GPSd and convert into three styles.

Add several (some undocumented) insertion tags that are required for the Winlink Check In form.

internal/forms/forms.go

@@ -17,6 +17,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"math"
 	"net/http"
 	"os"
 	"path"
@@ -29,7 +30,9 @@ import (
 	"time"
 	"unicode/utf8"
 
+	"github.com/la5nta/pat/cfg"
 	"github.com/dimchansky/utfbom"
+	"github.com/la5nta/pat/internal/gpsd"
 )
 
 const (
@@ -59,6 +62,7 @@ type Config struct {
 	AppVersion string
 	LineReader func() string
 	UserAgent  string
+	GPSd       cfg.GPSdConfig
 }
 
 // Form holds information about a Winlink form template
@@ -704,6 +708,103 @@ func (m *Manager) findAbsPathForTemplatePath(tmplPath string) (string, error) {
 	return retVal, nil
 }
 
+func (m *Manager) gpsPos() (gpsd.Position, error)  {
+	// return current GPS Position
+
+	addr := m.config.GPSd.Addr
+	if addr != "" {
+		conn, err := gpsd.Dial(addr)
+		if err != nil {
+			log.Printf("GPSd daemon: %s", err)
+		}
+		defer conn.Close()
+
+		conn.Watch(true)
+
+		log.Println("Waiting for position from GPSd...")
+		pos, err := conn.NextPosTimeout(3 * time.Second) // TODO: configurable
+		if err != nil {
+			log.Printf("GPSd: %s", err)
+		} else {
+			log.Printf("GPSd: %f %f", pos.Lat, pos.Lon)
+		}
+		return pos, err
+	} else {
+		return gpsd.Position{}, errors.New("GPSd: not configured.")
+	}
+}
+
+type gpsStyle int
+
+const (
+	// documentation: https://www.winlink.org/sites/default/files/RMSE_FORMS/insertion_tags.zip
+        signedDecimal gpsStyle = iota // 41.1234 -73.4567
+        decimal			      // 46.3795N 121.5835W
+	degreeMinute		      // 46-22.77N 121-35.01W
+)
+
+func gpsFmt(style gpsStyle, pos gpsd.Position) string {
+	var northing string
+	var easting string
+	var latDegrees int
+	var latMinutes float64
+	var lonDegrees int
+	var lonMinutes float64
+
+	noPos := gpsd.Position{}
+	if pos == noPos {
+		return "(Not available)"
+	}
+	switch style {
+	case degreeMinute: {
+		latDegrees = int(math.Trunc(math.Abs(pos.Lat)))
+		latMinutes = (math.Abs(pos.Lat) - float64(latDegrees)) * 60
+		lonDegrees = int(math.Trunc(math.Abs(pos.Lon)))
+		lonMinutes = (math.Abs(pos.Lon) - float64(lonDegrees)) * 60
+	}
+		fallthrough
+	case decimal: {
+		if pos.Lat >= 0 {
+			northing = "N"
+		} else {
+			northing = "S"
+		}
+		if pos.Lon >= 0 {
+			easting = "E"
+		} else {
+			easting = "W"
+		}
+	}
+	}
+
+	switch style {
+	case signedDecimal: return fmt.Sprintf("%.4f %.4f",pos.Lat,pos.Lon)
+	case decimal: return fmt.Sprintf("%.4f%s %.4f%s", math.Abs(pos.Lat), northing, math.Abs(pos.Lon), easting)
+	case degreeMinute: return fmt.Sprintf("%02d-%05.2f%s %03d-%05.2f%s", latDegrees, latMinutes, northing, lonDegrees, lonMinutes, easting)
+	default: return "(Not available)"
+	}
+}
+
+func posToGridSquare(pos gpsd.Position) string {
+	// function translated from Winlink_Check_In_Intial.html
+	var (
+		U = "ABCDEFGHIJKLMNOPQRSTUVWX"
+		L = "abcdefghijklmnopqrstuvwx"
+		grid string
+	)
+	adjLat := pos.Lat + 90.0
+	adjLon := pos.Lon + 180.0
+	grid = grid + string(U[int(adjLon/20.0)]) + string(U[int(adjLat/10.0)])
+	nLat := int(adjLat) % 10
+	nLon := int(adjLon/2) % 10
+	grid = grid + fmt.Sprintf("%d%d", nLon, nLat)
+	rLat := (adjLat - math.Trunc(adjLat)) * 60.0
+	rLon := (adjLon - 2 * math.Trunc(adjLon/2)) * 60.0
+	grid = grid + string(L[int(math.Trunc(rLon/5))]) + string(L[int(math.Trunc(rLat/2.5))])
+	return grid
+}
+
+
 func (m *Manager) fillFormTemplate(absPathTemplate string, formDestURL string, placeholderRegEx *regexp.Regexp, formVars map[string]string) (string, error) {
 	fUnsanitized, err := os.Open(absPathTemplate)
 	if err != nil {
@@ -732,6 +833,13 @@ func (m *Manager) fillFormTemplate(absPathTemplate string, formDestURL string, p
 	nowDateUTC := now.UTC().Format("2006-01-02Z")
 	nowTimeUTC := now.UTC().Format("15:04:05Z")
 	udtg := strings.ToUpper(now.UTC().Format("021504Z Jan 2006"))
+	nowPos,err := m.gpsPos()
+	var validPos string
+	if err != nil {
+		validPos = "NO"
+	} else {
+		validPos = "YES"
+	}
 
 	scanner := bufio.NewScanner(bytes.NewReader(sanitizedFileContent))
 	for scanner.Scan() {
@@ -749,6 +857,18 @@ func (m *Manager) fillFormTemplate(absPathTemplate string, formDestURL string, p
 		l = strings.ReplaceAll(l, "{UDTG}", udtg)
 		l = strings.ReplaceAll(l, "{Time}", nowTime)
 		l = strings.ReplaceAll(l, "{UTime}", nowTimeUTC)
+		l = strings.ReplaceAll(l, "{GPS}", gpsFmt(degreeMinute, nowPos))
+		l = strings.ReplaceAll(l, "{GPS_DECIMAL}", gpsFmt(decimal, nowPos))
+		l = strings.ReplaceAll(l, "{GPS_SIGNED_DECIMAL}", gpsFmt(signedDecimal, nowPos))
+		// Lots of undocumented tags found in the Winlink check in form.
+		// Note also various ways of capitalizing. Perhaps best to do case insenstive string replacements....
+		l = strings.ReplaceAll(l, "{Latitude}", fmt.Sprintf("%.4f", nowPos.Lat))
+		l = strings.ReplaceAll(l, "{latitude}", fmt.Sprintf("%.4f", nowPos.Lat))
+		l = strings.ReplaceAll(l, "{Longitude}", fmt.Sprintf("%.4f", nowPos.Lon))
+		l = strings.ReplaceAll(l, "{longitude}", fmt.Sprintf("%.4f", nowPos.Lon))
+		l = strings.ReplaceAll(l, "{GridSquare}", posToGridSquare(nowPos))
+		l = strings.ReplaceAll(l, "{GPSValid}", fmt.Sprintf("%s ", validPos))
+		// l = strings.ReplaceAll(l, "{InternetAvailable}", "TO DO")
 		if placeholderRegEx != nil {
 			l = fillPlaceholders(l, placeholderRegEx, formVars)
 		}

main.go

@@ -325,6 +325,7 @@ func main() {
 		AppVersion: buildinfo.VersionStringShort(),
 		UserAgent:  buildinfo.UserAgent(),
 		LineReader: readLine,
+		GPSd:       config.GPSd,
 	})
 
 	// Make sure we clean up on exit, closing any open resources etc.