From 6ad523e0eab227f7a40906aba2951d950d0181f7 Mon Sep 17 00:00:00 2001
From: Alan Crosswell <alan@columbia.edu>
Date: Mon, 14 Mar 2022 18:22:21 -0400
Subject: [PATCH] Get Position from GPSd and convert into three styles.

---
 internal/forms/forms.go | 84 ++++++++++++++++++++++++++++-------------
 1 file changed, 58 insertions(+), 26 deletions(-)

diff --git a/internal/forms/forms.go b/internal/forms/forms.go
index 074f1472..da1f55e2 100644
--- a/internal/forms/forms.go
+++ b/internal/forms/forms.go
@@ -17,6 +17,7 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
+	"math"
 	"net/http"
 	"os"
 	"path"
@@ -705,21 +706,8 @@ func (m *Manager) findAbsPathForTemplatePath(tmplPath string) (string, error) {
 	return retVal, nil
 }
 
-func gpsPos(decimal bool, signed bool) string {
-	// return current GPS position in one of these alternative formats:
-	// decimal=false:              degrees-minutes.seconds w/Northing and Easting
-	// decimal=true, signed=false: degrees.fraction w/Northing and Easting
-	// decimal=true, signed=true:  degrees.fraction w/minus sign for South and West
-
-	// documentation: https://www.winlink.org/sites/default/files/RMSE_FORMS/insertion_tags.zip
-	// <GPS> - Inserts the current GPS location (if available)
-	// Ex: 46-22.77N 121-35.01W
-	// <GPS_DECIMAL> - Inserts the current GPS location (if available)
-	// Ex: 46-22.77N 121-35.01W (this example is probably incorrect)
-	// Ex: 46.3795N 121.5835W
-	// <GPS_SIGNED_DECIMAL> - Inserts the current GPS location as a signed decimal latitude/longitude (if available)
-	// Ex: 46.3795 -121.5835
-
+func gpsPos() (gpsd.Position, error)  {
+	// return current GPS Position
 
 	addr := "localhost:2947" // TODO: get from config
 	if addr != "" {
@@ -736,12 +724,58 @@ func gpsPos(decimal bool, signed bool) string {
 		if err != nil {
 			log.Fatalf("GPSd: %s", err)
 		}
+		return pos, err
+	} else {
+		return gpsd.Position{}, errors.New("GPSd: not configured.")
+	}
+}
 
-		log.Printf("GPS pos: %f %f", pos.Lat, pos.Lon)
-		if decimal && signed {
-			return fmt.Sprintf("%f %f", pos.Lat, pos.Lon)
-		} else {
-			return "TBD"
+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 {
+		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("%d-%.4f%s %d-%.4f%s", latDegrees, latMinutes, northing, lonDegrees, lonMinutes, easting)
+		default: return "(Not available)"
 		}
 	} else {
 		return "(Not available)"
@@ -776,9 +810,7 @@ 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"))
-	nowGPS := gpsPos(false, false)
-	nowGPSDecimal := gpsPos(true, false)
-	nowGPSSignedDecimal := gpsPos(true, true)
+	nowPos,err := gpsPos()
 
 	scanner := bufio.NewScanner(bytes.NewReader(sanitizedFileContent))
 	for scanner.Scan() {
@@ -796,9 +828,9 @@ 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}", nowGPS)
-		l = strings.ReplaceAll(l, "{GPS_DECIMAL}", nowGPSDecimal)
-		l = strings.ReplaceAll(l, "{GPS_SIGNED_DECIMAL}", nowGPSSignedDecimal)
+		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))
 		if placeholderRegEx != nil {
 			l = fillPlaceholders(l, placeholderRegEx, formVars)
 		}