From 91d0a73cd29cb1a262532fef25baf1f45d1b64ce Mon Sep 17 00:00:00 2001
From: Morten <mnielsen@esri.com>
Date: Wed, 3 Aug 2022 13:55:04 -0700
Subject: [PATCH] Handle empty GGA message

Fixes #105
---
 src/NmeaParser/Nmea/Gga.cs                    |  3 ++-
 .../NmeaParser.Tests/NmeaMessages.cs          | 22 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/NmeaParser/Nmea/Gga.cs b/src/NmeaParser/Nmea/Gga.cs
index c0d32f4..137489e 100644
--- a/src/NmeaParser/Nmea/Gga.cs
+++ b/src/NmeaParser/Nmea/Gga.cs
@@ -40,7 +40,8 @@ namespace NmeaParser.Messages
             FixTime = StringToTimeSpan(message[0]);
             Latitude = NmeaMessage.StringToLatitude(message[1], message[2]);
             Longitude = NmeaMessage.StringToLongitude(message[3], message[4]);
-            Quality =  (Gga.FixQuality)int.Parse(message[5], CultureInfo.InvariantCulture);
+            if (!string.IsNullOrEmpty(message[5]))
+                Quality =  (Gga.FixQuality)int.Parse(message[5], CultureInfo.InvariantCulture);
             if (!string.IsNullOrEmpty(message[6]))
                 NumberOfSatellites = int.Parse(message[6], CultureInfo.InvariantCulture);
             Hdop = NmeaMessage.StringToDouble(message[7]);
diff --git a/src/UnitTests/NmeaParser.Tests/NmeaMessages.cs b/src/UnitTests/NmeaParser.Tests/NmeaMessages.cs
index 5c60c32..4154345 100644
--- a/src/UnitTests/NmeaParser.Tests/NmeaMessages.cs
+++ b/src/UnitTests/NmeaParser.Tests/NmeaMessages.cs
@@ -261,6 +261,28 @@ namespace NmeaParser.Tests
             Assert.AreEqual(0, gga.NumberOfSatellites);
         }
 
+
+        [TestMethod]
+        public void TestGPGGA_Empty()
+        {
+            string input = "$GPGGA,,,,,,,,,,,,,,*56";
+            var msg = NmeaMessage.Parse(input);
+            Assert.IsInstanceOfType(msg, typeof(Gga));
+            Gga gga = (Gga)msg;
+            Assert.AreEqual(0, gga.NumberOfSatellites);
+            Assert.AreEqual(Gga.FixQuality.Invalid, gga.Quality);
+            Assert.IsTrue(double.IsNaN(gga.GeoidalSeparation));
+            Assert.AreEqual(string.Empty, gga.GeoidalSeparationUnits);
+            Assert.IsTrue(double.IsNaN(gga.Longitude));
+            Assert.IsTrue(double.IsNaN(gga.Latitude));
+            Assert.IsTrue(double.IsNaN(gga.Altitude));
+            Assert.AreEqual(string.Empty, gga.AltitudeUnits);
+            Assert.IsTrue(double.IsNaN(gga.Hdop));
+            Assert.IsNull(gga.TimeSinceLastDgpsUpdate);
+            Assert.AreEqual(TimeSpan.Zero, gga.FixTime);
+            Assert.AreEqual(-1, gga.DgpsStationId);
+        }
+
         [TestMethod]
         public void TestPtlna()
         {