Refactor and complete providers

pkg/weather/enrich.go

@@ -0,0 +1,54 @@
+package weather
+
+import "math"
+
+// Attempts to complete missing fields that may not
+// be set by a specific provider, such as DewPoint and WindChill
+//
+// If enrich is called repeated with the same station ID, measurements
+// will be recorded to produce averages. This will be more stable
+// and support scaling if Redis is available
+// TODO: Implement average tracker
+func (u *WeatherUpdate) Enrich() {
+	if u.WindChillF == 0 {
+		u.WindChillF = CalculateWindChill(u.TempF, u.WindSpeedMPH)
+	}
+
+	if u.DewPointF == 0 {
+		u.DewPointF = CalculateDewPoint(u.TempF, float32(u.Humidity))
+	}
+
+	if u.BaromAbsoluteIn == 0 {
+		u.BaromAbsoluteIn = u.BaromRelativeIn
+	}
+}
+
+func CalculateDewPoint(tempF, humidity float32) float32 {
+	// Convert temperature from Fahrenheit to Celsius
+	tempC := (tempF - 32) * 5 / 9
+
+	// Calculate the dew point using the Magnus-Tetens approximation
+	a := float32(17.27)
+	b := float32(237.7)
+
+	alpha := (a*tempC)/(b+tempC) + float32(math.Log(float64(humidity)/100))
+	dewPointC := (b * alpha) / (a - alpha)
+
+	// Convert dew point back to Fahrenheit
+	dewPointF := (dewPointC * 9 / 5) + 32
+	return dewPointF
+}
+
+func CalculateWindChill(tempF float32, windSpeedMPH float32) float32 {
+	if windSpeedMPH <= 3 {
+		// Wind chill calculation doesn't apply for very low wind speeds
+		return tempF
+	}
+
+	// Formula for calculating wind chill
+	return float32(
+		35.74 + 0.6215*float64(tempF) -
+			35.75*math.Pow(float64(windSpeedMPH), 0.16) +
+			0.4275*float64(tempF)*
+				math.Pow(float64(windSpeedMPH), 0.16))
+}