Server/internal/color/color.go

package color

import (
	"fmt"
	"github.com/lucasb-eyer/go-colorful"
	"strconv"
	"strings"
)

type Color struct {
	RGB *RGB    `json:"rgb,omitempty"`
	HS  *HueSat `json:"hs,omitempty"`
	K   *int    `json:"k,omitempty"`
	XY  *XY     `json:"xy,omitempty"`
}

func (col *Color) IsHueSat() bool {
	return col.HS != nil
}

func (col *Color) IsHueSatKelvin() bool {
	return col.HS != nil && col.K != nil
}

func (col *Color) IsKelvin() bool {
	return col.K != nil
}

func (col *Color) IsEmpty() bool {
	return *col == Color{}
}

func (col *Color) SetK(k int) {
	*col = Color{K: &k}
}

func (col *Color) SetXY(xy XY) {
	*col = Color{XY: &xy}
}

// ToRGB tries to copy the color to an RGB color. If it's already RGB, it will be plainly copied, but HS
// will be returned. If ok is false, then no copying has occurred and cv2 will be blank.
func (col *Color) ToRGB() (col2 Color, ok bool) {
	if col.RGB != nil {
		rgb := *col.RGB
		col2 = Color{RGB: &rgb}
		ok = true
	} else if col.HS != nil {
		rgb := col.HS.ToRGB()
		col2 = Color{RGB: &rgb}
		ok = true
	} else if col.XY != nil {
		rgb := col.XY.ToRGB()
		col2 = Color{RGB: &rgb}
		ok = true
	}

	return
}

func (col *Color) ToHS() (col2 Color, ok bool) {
	if col.HS != nil {
		hs := *col.HS
		col2 = Color{HS: &hs}
		ok = true
	} else if col.RGB != nil {
		hs := col.RGB.ToHS()
		col2 = Color{HS: &hs}
		ok = true
	} else if col.XY != nil {
		hs := col.XY.ToHS()
		col2 = Color{HS: &hs}
		ok = true
	}

	return
}

func (col *Color) ToHSK() (col2 Color, ok bool) {
	k := 4000

	if col.HS != nil {
		hs := *col.HS
		col2 = Color{HS: &hs}

		if col.K != nil {
			k = *col.K
		}
		col2.K = &k

		ok = true
	} else if col.RGB != nil {
		hs := col.RGB.ToHS()
		col2 = Color{HS: &hs}
		col2.K = &k
		ok = true
	} else if col.XY != nil {
		hs := col.XY.ToHS()
		col2 = Color{HS: &hs}
		col2.K = &k
		ok = true
	} else if col.K != nil {
		k = *col.K
		col2.HS = &HueSat{Hue: 0, Sat: 0}
		col2.K = &k
		ok = true
	}

	return
}

// ToXY tries to copy the color to an XY color.
func (col *Color) ToXY() (col2 Color, ok bool) {
	if col.XY != nil {
		xy := *col.XY
		col2 = Color{XY: &xy}
		ok = true
	} else if col.HS != nil {
		xy := col.HS.ToXY()
		col2 = Color{XY: &xy}
		ok = true
	} else if col.RGB != nil {
		xy := col.RGB.ToXY()
		col2 = Color{XY: &xy}
		ok = true
	}

	return
}

func (col *Color) Interpolate(other Color, fac float64) Color {
	// Special case for kelvin values.
	if col.IsKelvin() && other.IsKelvin() {
		k1 := *col.K
		k2 := *col.K
		k3 := k1 + int(float64(k2-k1)*fac)
		return Color{K: &k3}
	}

	// Get the colorful values.
	cvCF := col.colorful()
	otherCF := other.colorful()

	// Blend and normalize
	blended := cvCF.BlendLuv(otherCF, fac)
	blendedHue, blendedSat, _ := blended.Hsv()
	blendedHs := HueSat{Hue: blendedHue, Sat: blendedSat}

	// Convert to the first's type
	switch col.Kind() {
	case "rgb":
		rgb := blendedHs.ToRGB()
		return Color{RGB: &rgb}
	case "xy":
		xy := blendedHs.ToXY()
		return Color{XY: &xy}
	default:
		return Color{HS: &blendedHs}
	}
}

func (col *Color) Kind() string {
	switch {
	case col.RGB != nil:
		return "rgb"
	case col.XY != nil:
		return "xy"
	case col.HS != nil && col.K != nil:
		return "hsk"
	case col.HS != nil:
		return "hs"
	case col.K != nil:
		return "k"
	default:
		return ""
	}
}

func (col *Color) String() string {
	switch {
	case col.RGB != nil:
		return fmt.Sprintf("rgb:%.3f,%.3f,%.3f", col.RGB.Red, col.RGB.Green, col.RGB.Blue)
	case col.XY != nil:
		return fmt.Sprintf("xy:%.4f,%.4f", col.XY.X, col.XY.Y)
	case col.HS != nil && col.K != nil:
		return fmt.Sprintf("hsk:%.4f,%.3f,%d", col.HS.Hue, col.HS.Sat, *col.K)
	case col.HS != nil:
		return fmt.Sprintf("hs:%.4f,%.3f", col.HS.Hue, col.HS.Sat)
	case col.K != nil:
		return fmt.Sprintf("k:%d", *col.K)
	default:
		return ""
	}
}

func (col *Color) colorful() colorful.Color {
	switch {
	case col.HS != nil:
		return colorful.Hsv(col.HS.Hue, col.HS.Sat, 1)
	case col.RGB != nil:
		return colorful.Color{R: col.RGB.Red, G: col.RGB.Green, B: col.RGB.Blue}
	case col.XY != nil:
		return colorful.Xyy(col.XY.X, col.XY.Y, 0.5)
	default:
		return colorful.Color{R: 255, B: 255, G: 255}
	}
}

func MustParse(raw string) Color {
	col, err := Parse(raw)
	if err != nil {
		panic(err)
	}

	return col
}

func Parse(raw string) (col Color, err error) {
	if raw == "" {
		return
	}

	tokens := strings.SplitN(raw, ":", 2)
	if len(tokens) != 2 {
		err = ErrBadColorInput
		return
	}

	switch tokens[0] {
	case "kelvin", "k":
		{
			parsedPart, err := strconv.Atoi(tokens[1])
			if err != nil {
				err = ErrBadColorInput
				break
			}

			col.K = &parsedPart
		}

	case "xy":
		{
			parts := strings.Split(tokens[1], ",")
			if len(parts) < 2 {
				err = ErrUnknownColorFormat
				return
			}

			x, err1 := strconv.ParseFloat(parts[0], 64)
			y, err2 := strconv.ParseFloat(parts[1], 64)
			if err1 != nil || err2 != nil {
				err = ErrBadColorInput
				break
			}

			col.XY = &XY{x, y}
		}

	case "hs":
		{
			parts := strings.Split(tokens[1], ",")
			if len(parts) < 2 {
				err = ErrUnknownColorFormat
				return
			}

			part1, err1 := strconv.ParseFloat(parts[0], 64)
			part2, err2 := strconv.ParseFloat(parts[1], 64)
			if err1 != nil || err2 != nil {
				err = ErrBadColorInput
				break
			}

			col.HS = &HueSat{Hue: part1, Sat: part2}
		}

	case "hsk":
		{
			parts := strings.Split(tokens[1], ",")
			if len(parts) < 3 {
				err = ErrUnknownColorFormat
				return
			}

			part1, err1 := strconv.ParseFloat(parts[0], 64)
			part2, err2 := strconv.ParseFloat(parts[1], 64)
			part3, err3 := strconv.Atoi(parts[2])
			if err1 != nil || err2 != nil || err3 != nil {
				err = ErrBadColorInput
				break
			}

			col.HS = &HueSat{Hue: part1, Sat: part2}
			col.K = &part3
		}

	case "rgb":
		{
			if strings.HasPrefix(tokens[1], "#") {
				hex := tokens[1][1:]
				if !validHex(hex) {
					err = ErrBadColorInput
					break
				}

				if len(hex) == 6 {
					col.RGB = &RGB{
						Red:   float64(hex2num(hex[0:2])) / 255.0,
						Green: float64(hex2num(hex[2:4])) / 255.0,
						Blue:  float64(hex2num(hex[4:6])) / 255.0,
					}
				} else if len(hex) == 3 {
					col.RGB = &RGB{
						Red:   float64(hex2digit(hex[0])) / 15.0,
						Green: float64(hex2digit(hex[1])) / 15.0,
						Blue:  float64(hex2digit(hex[2])) / 15.0,
					}
				} else {
					err = ErrUnknownColorFormat
					return
				}
			} else {
				parts := strings.Split(tokens[1], ",")
				if len(parts) < 3 {
					err = ErrUnknownColorFormat
					return
				}

				part1, err1 := strconv.ParseFloat(parts[0], 64)
				part2, err2 := strconv.ParseFloat(parts[1], 64)
				part3, err3 := strconv.ParseFloat(parts[2], 64)
				if err1 != nil || err2 != nil || err3 != nil {
					err = ErrBadColorInput
					break
				}

				col.RGB = &RGB{Red: part1, Green: part2, Blue: part3}
			}

			normalizedRGB := col.RGB.ToHS().ToRGB()
			col.RGB = &normalizedRGB
		}

	default:
		err = ErrUnknownColorFormat
	}

	return
}

func validHex(h string) bool {
	for _, ch := range h {
		if !((ch >= 'a' && ch <= 'f') || (ch >= '0' || ch <= '9')) {
			return false
		}
	}

	return true
}

func hex2num(s string) int {
	v := 0
	for _, h := range s {
		v *= 16
		v += hex2digit(byte(h))
	}

	return v
}

func hex2digit(h byte) int {
	if h >= 'a' && h <= 'f' {
		return 10 + int(h-'a')
	} else {
		return int(h - '0')
	}
}