add support for GPHDT message

README.md

@@ -27,6 +27,7 @@ At this moment, this library supports the following sentence types:
 - [GPVTG](http://aprs.gids.nl/nmea/#vtg) - Track Made Good and Ground Speed
 - [GPZDA](http://aprs.gids.nl/nmea/#zda) - Date & time data
 - [PGRME](http://aprs.gids.nl/nmea/#rme) - Estimated Position Error (Garmin proprietary sentence)
+- [GPHDT](http://aprs.gids.nl/nmea/#hdt) - Actual vessel heading in degrees True
 
 
 ## Example

gphdt.go

@@ -0,0 +1,25 @@
+package nmea
+
+const (
+	// PrefixGPHDT prefix of GPHDT sentence type
+	PrefixGPHDT = "GPHDT"
+)
+
+// GPHDT is the Actual vessel heading in degrees True.
+// http://aprs.gids.nl/nmea/#hdt
+type GPHDT struct {
+	BaseSentence
+	Heading float64 // Heading in degrees
+	True    bool    // heading relative to true north if T
+}
+
+// newGPHDT constructor
+func newGPHDT(s BaseSentence) (GPHDT, error) {
+	p := newParser(s, PrefixGPHDT)
+	m := GPHDT{
+		BaseSentence: s,
+		Heading:      p.Float64(0, "heading"),
+		True:         p.EnumString(1, "true", "T") == "T",
+	}
+	return m, p.Err()
+}

gphdt_test.go

@@ -0,0 +1,50 @@
+package nmea
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var gphdttests = []struct {
+	name string
+	raw  string
+	err  string
+	msg  GPHDT
+}{
+	{
+		name: "good sentence",
+		raw:  "$GPHDT,123.456,T*32",
+		msg: GPHDT{
+			Heading: 123.456,
+			True:    true,
+		},
+	},
+	{
+		name: "invalid True",
+		raw:  "$GPHDT,123.456,X*3E",
+		err:  "nmea: GPHDT invalid true: X",
+	},
+	{
+		name: "invalid Heading",
+		raw:  "$GPHDT,XXX,T*43",
+		err:  "nmea: GPHDT invalid heading: XXX",
+	},
+}
+
+func TestGPHDT(t *testing.T) {
+	for _, tt := range gphdttests {
+		t.Run(tt.name, func(t *testing.T) {
+			m, err := Parse(tt.raw)
+			if tt.err != "" {
+				assert.Error(t, err)
+				assert.EqualError(t, err, tt.err)
+			} else {
+				assert.NoError(t, err)
+				gphdt := m.(GPHDT)
+				gphdt.BaseSentence = BaseSentence{}
+				assert.Equal(t, tt.msg, gphdt)
+			}
+		})
+	}
+}

sentence.go

@@ -104,6 +104,8 @@ func Parse(raw string) (Sentence, error) {
 		return newGPGSV(s)
 	case PrefixGLGSV:
 		return newGLGSV(s)
+	case PrefixGPHDT:
+		return newGPHDT(s)
 	default:
 		return nil, fmt.Errorf("nmea: sentence type '%s' not implemented", s.Type)
 	}