Move all CT functionality into colortemp.go

1 files changed, 27 insertions, 0 deletions

diff --git a/colortemp.go b/colortemp.go
index d621043..051ca54 100644
--- a/colortemp.go
+++ b/colortemp.go
@@ -1,7 +1,10 @@
 package main
 
 import (
+	"math"
 	"time"
+
+	hue "github.com/benburwell/gohue"
 )
 
 type ColorTemperature uint
@@ -9,3 +12,27 @@ type ColorTemperature uint
 func getDesiredColorTemperature(at time.Time) ColorTemperature {
 	return 1800
 }
+
+// Translate a desired color temperature in Kelvins to a value comprehensible
+// by a Hue luminaire. According to Hue documentation, the value 153
+// corresponds to 6500K, and 500 corresponds to 2000K. Using these known
+// values, we'll create a mapping between spaces, and additionally limit the
+// resulting value by the range that the luminaire supports.
+//
+//   153 <=> 6500K
+//   500 <=> 2000K
+//   =============
+//   347     4500
+func translateCtForLight(ct ColorTemperature, light hue.Light) uint16 {
+	divisor := 12.968
+	scaled := float64(ct) / divisor
+	inverted := 500 - scaled + 153
+	min := float64(light.Capabilities.Control.CT.Min)
+	max := float64(light.Capabilities.Control.CT.Max)
+	return uint16(math.Max(min, math.Min(max, inverted)))
+}
+
+// Determine whether there is a non-zero color temperature range for the given light
+func supportsColorTemp(l hue.Light) bool {
+	return l.Capabilities.Control.CT.Max > l.Capabilities.Control.CT.Min
+}