fix: pass null through true/mag conversions

Input value null should result in null output values.

Fixes #120.

README.md

@@ -24,7 +24,7 @@ It currently calculates:
  * True Wind Direction (based on AWA and headingTrue)
  * Ground Wind Angle and Speed (based on SOG, AWA and AWS)
  * Magnetic Wind Direction (based on AWA and headingMagnetic)
- * Magnetic Wind Direction (based on wind.directionTrue and magneticVarition)
+ * Magnetic Wind Direction (based on wind.directionTrue and magneticVariation)
  * Wind Shift (experimental)
  * Moon illumination and times (based on time and navigation.position)
  * Sunlight Times: sunrise, sunriseEnd, goldenHourEnd, solarNoon, goldenHour, sunsetStart, sunset, dusk, nauticalDusk, night, nadir, nightEnd, nauticalDawn, dawn (based on time and navigation.position)

calcs/courseOverGroundMagnetic.js

@@ -19,6 +19,12 @@ module.exports = function (app, plugin) {
           return
         }
       }
+      if (
+        _.isUndefined(courseOverGroundTrue) ||
+        courseOverGroundTrue === null
+      ) {
+        return [{ path: 'navigation.courseOverGroundMagnetic', value: null }]
+      }
       var courseOverGroundMagnetic = courseOverGroundTrue - magneticVariation
       if (courseOverGroundMagnetic < 0) {
         courseOverGroundMagnetic = Math.PI * 2 + courseOverGroundMagnetic
@@ -36,6 +42,10 @@ module.exports = function (app, plugin) {
       {
         input: [1.0, 0.1],
         expected: [{ path: 'navigation.courseOverGroundMagnetic', value: 0.9 }]
+      },
+      {
+        input: [null, -0.01],
+        expected: [{ path: 'navigation.courseOverGroundMagnetic', value: null }]
       }
     ]
   }

calcs/courseOverGroundTrue.js

@@ -19,6 +19,12 @@ module.exports = function (app, plugin) {
           return
         }
       }
+      if (
+        _.isUndefined(courseOverGroundMagnetic) ||
+        courseOverGroundMagnetic === null
+      ) {
+        return [{ path: 'navigation.courseOverGroundTrue', value: null }]
+      }
       var courseOverGroundTrue = courseOverGroundMagnetic + magneticVariation
       if (courseOverGroundTrue < 0) {
         courseOverGroundTrue = Math.PI * 2 + courseOverGroundTrue
@@ -28,6 +34,12 @@ module.exports = function (app, plugin) {
       return [
         { path: 'navigation.courseOverGroundTrue', value: courseOverGroundTrue }
       ]
-    }
+    },
+    tests: [
+      {
+        input: [null, 0.01],
+        expected: [{ path: 'navigation.courseOverGroundTrue', value: null }]
+      }
+    ]
   }
 }

calcs/headingTrue.js

@@ -16,13 +16,22 @@ module.exports = function (app, plugin) {
           return
         }
       }
+      if (_.isUndefined(heading) || heading === null) {
+        return [{ path: 'navigation.headingTrue', value: null }]
+      }
       var headingTrue = heading + magneticVariation
       if (headingTrue < 0) {
         headingTrue = Math.PI * 2 + headingTrue
       } else if (headingTrue > Math.PI * 2) {
         headingTrue = headingTrue - Math.PI * 2
       }
       return [{ path: 'navigation.headingTrue', value: headingTrue }]
-    }
+    },
+    tests: [
+      {
+        input: [null, 0.01],
+        expected: [{ path: 'navigation.headingTrue', value: null }]
+      }
+    ]
   }
 }

calcs/windDirectionMagnetic.js

@@ -8,6 +8,9 @@ module.exports = function (app, plugin) {
       'navigation.magneticVariation'
     ],
     calculator: function (directionTrue, magneticVariation) {
+      if (directionTrue === null) {
+        return [{ path: 'environment.wind.directionMagnetic', value: null }]
+      }
       var directionMagnetic = directionTrue - magneticVariation
       if (directionMagnetic < 0) {
         directionMagnetic = Math.PI * 2 + directionMagnetic
@@ -17,6 +20,12 @@ module.exports = function (app, plugin) {
       return [
         { path: 'environment.wind.directionMagnetic', value: directionMagnetic }
       ]
-    }
+    },
+    tests: [
+      {
+        input: [null, -0.01],
+        expected: [{ path: 'environment.wind.directionMagnetic', value: null }]
+      }
+    ]
   }
 }