Add support for color

xy decoding is a pain to decode. Thanks to chatgpt, I was able to port
the JS code. The code seems to works fine now.

I need to fix a issue in the xAAL core due to compare of list..

utils.go

 package main
 
-import "strconv"
+import (
+	"math"
+	"strconv"
+
+	"github.com/lucasb-eyer/go-colorful"
+)
 
 func hexStringToInteger(hexString string) (uint64, error) {
 	// Drop the "0x" prefix if it exists
@@ -15,3 +20,56 @@ func hexStringToInteger(hexString string) (uint64, error) {
 	}
 	return integerValue, nil
 }
+
+// xyToColor converts CIE XY color coordinates and brightness to an RGB color using the go-colorful library.
+// https://github.com/Koenkk/zigbee2mqtt/issues/3497
+func xyToColor(x, y, brightness float64) colorful.Color {
+	// Set maximum brightness if not provided (assuming brightness is in the range 0-254)
+	if brightness == 0 {
+		brightness = 254
+	}
+
+	// Calculate z, X, Y, and Z values for the XYZ color space
+	z := 1.0 - x - y
+	Y := brightness / 254.0 // Normalize brightness
+	X := (Y / y) * x
+	Z := (Y / y) * z
+
+	// Convert XYZ to RGB using Wide RGB D65 conversion
+	red := X*1.656492 - Y*0.354851 - Z*0.255038
+	green := -X*0.707196 + Y*1.655397 + Z*0.036152
+	blue := X*0.051713 - Y*0.121364 + Z*1.011530
+
+	// If any color component is larger than 1.0, scale it back to 1.0 and adjust others accordingly
+	if red > blue && red > green && red > 1.0 {
+		green = green / red
+		blue = blue / red
+		red = 1.0
+	} else if green > blue && green > red && green > 1.0 {
+		red = red / green
+		blue = blue / green
+		green = 1.0
+	} else if blue > red && blue > green && blue > 1.0 {
+		red = red / blue
+		green = green / blue
+		blue = 1.0
+	}
+
+	// Apply reverse gamma correction to each component
+	applyGamma := func(value float64) float64 {
+		if value <= 0.0031308 {
+			return 12.92 * value
+		}
+		return (1.0+0.055)*math.Pow(value, 1.0/2.4) - 0.055
+	}
+
+	red = applyGamma(red)
+	green = applyGamma(green)
+	blue = applyGamma(blue)
+	return colorful.Color{R: red, G: green, B: blue}
+}
+
+func roundToDecimal(value float64, places int) float64 {
+	pow := math.Pow(10, float64(places))
+	return math.Round(value*pow) / pow
+}

xaal.go

@@ -6,6 +6,7 @@ import (
 	"math"
 
 	"github.com/davecgh/go-spew/spew"
+	"github.com/lucasb-eyer/go-colorful"
 	"gitlab.imt-atlantique.fr/xaal/code/go/core/schemas"
 	"gitlab.imt-atlantique.fr/xaal/code/go/core/uuid"
 	"gitlab.imt-atlantique.fr/xaal/code/go/core/xaal"
@@ -252,7 +253,7 @@ func NewLamp(addr uuid.UUID, zDev *Z2MDevice, expose *Expose) XAALDeviceInterfac
 	}
 	if expose.GetFeature("color_xy") != nil {
 		dev.DevType = "lamp.color"
-		dev.AddAttribute("hsv", nil)
+		dev.AddAttribute("hsv", []float64{0, 0, 0})
 		dev.AddAttribute("mode", nil)
 		dev.UnsupportedAttributes = []string{"scene"}
 		dev.AddMethod("set_hsv", dev.setHSV)
@@ -281,6 +282,23 @@ func (dev *Lamp) update(payload map[string]interface{}) {
 		brightness = brightness / 255 * 100
 		dev.GetAttribute("brightness").SetValue(int(brightness))
 	}
+	// color
+	color, exists := payload["color"].(map[string]interface{})
+	if exists {
+		x, _ := color["x"].(float64)
+		y, _ := color["y"].(float64)
+		brigthness, _ := payload["brightness"].(float64)
+		value := xyToColor(x, y, brigthness)
+		slog.Warn("color", "color", value.Hex(), "x", x, "y", y, "tmp", brigthness)
+		hue, sat, val := value.Hsv()
+		hue = roundToDecimal(hue, 1)
+		sat = roundToDecimal(sat, 2)
+		val = roundToDecimal(val, 2)
+		slog.Warn("color", "hue", hue, "sat", sat, "val", val)
+		dev.GetAttribute("hsv").SetValue([]float64{hue, sat, val})
+		return
+	}
+
 	// color_temp
 	color_temp, exists := payload["color_temp"].(float64)
 	if exists {
@@ -324,7 +342,15 @@ func (dev *Lamp) setWhiteTemperature(body xaal.MessageBody) *xaal.MessageBody {
 }
 
 func (dev *Lamp) setHSV(body xaal.MessageBody) *xaal.MessageBody {
-	spew.Dump(body)
+	value, exist := body["hsv"].([]interface{})
+	if exist {
+		hue := float64(value[0].(uint64))
+		sat := value[1].(float64)
+		val := value[2].(float64)
+		color := colorful.Hsv(hue, sat, val)
+		slog.Debug("setHSV", "color", color.Hex(), "hue", hue, "sat", sat, "val", val)
+		dev.Z2MDevice.Set(fmt.Sprintf(`{"color": { "hex": "%s" }}`, color.Hex()))
+	}
 	return nil
 }