core: make label a common type, in a similar fashion as for status (#1252)

This will be useful for Board, and likely code review support later

2 files changed, 130 insertions, 0 deletions

diff --git a/entities/common/label.go b/entities/common/label.go
new file mode 100644
index 00000000..92d6c242
--- /dev/null
+++ b/entities/common/label.go
@@ -0,0 +1,95 @@
+package common
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"image/color"
+
+	fcolor "github.com/fatih/color"
+
+	"github.com/git-bug/git-bug/util/text"
+)
+
+type Label string
+
+func (l Label) String() string {
+	return string(l)
+}
+
+// RGBA from a Label computed in a deterministic way
+func (l Label) Color() LabelColor {
+	// colors from: https://material-ui.com/style/color/
+	colors := []LabelColor{
+		{R: 244, G: 67, B: 54, A: 255},   // red
+		{R: 233, G: 30, B: 99, A: 255},   // pink
+		{R: 156, G: 39, B: 176, A: 255},  // purple
+		{R: 103, G: 58, B: 183, A: 255},  // deepPurple
+		{R: 63, G: 81, B: 181, A: 255},   // indigo
+		{R: 33, G: 150, B: 243, A: 255},  // blue
+		{R: 3, G: 169, B: 244, A: 255},   // lightBlue
+		{R: 0, G: 188, B: 212, A: 255},   // cyan
+		{R: 0, G: 150, B: 136, A: 255},   // teal
+		{R: 76, G: 175, B: 80, A: 255},   // green
+		{R: 139, G: 195, B: 74, A: 255},  // lightGreen
+		{R: 205, G: 220, B: 57, A: 255},  // lime
+		{R: 255, G: 235, B: 59, A: 255},  // yellow
+		{R: 255, G: 193, B: 7, A: 255},   // amber
+		{R: 255, G: 152, B: 0, A: 255},   // orange
+		{R: 255, G: 87, B: 34, A: 255},   // deepOrange
+		{R: 121, G: 85, B: 72, A: 255},   // brown
+		{R: 158, G: 158, B: 158, A: 255}, // grey
+		{R: 96, G: 125, B: 139, A: 255},  // blueGrey
+	}
+
+	id := 0
+	hash := sha256.Sum256([]byte(l))
+	for _, char := range hash {
+		id = (id + int(char)) % len(colors)
+	}
+
+	return colors[id]
+}
+
+func (l Label) Validate() error {
+	str := string(l)
+
+	if text.Empty(str) {
+		return fmt.Errorf("empty")
+	}
+
+	if !text.SafeOneLine(str) {
+		return fmt.Errorf("label has unsafe characters")
+	}
+
+	return nil
+}
+
+type LabelColor color.RGBA
+
+func (lc LabelColor) RGBA() color.RGBA {
+	return color.RGBA(lc)
+}
+
+func (lc LabelColor) Term256() Term256 {
+	red := Term256(lc.R) * 6 / 256
+	green := Term256(lc.G) * 6 / 256
+	blue := Term256(lc.B) * 6 / 256
+
+	return red*36 + green*6 + blue + 16
+}
+
+type Term256 int
+
+func (t Term256) Escape() string {
+	if fcolor.NoColor {
+		return ""
+	}
+	return fmt.Sprintf("\x1b[38;5;%dm", t)
+}
+
+func (t Term256) Unescape() string {
+	if fcolor.NoColor {
+		return ""
+	}
+	return "\x1b[0m"
+}
diff --git a/entities/common/label_test.go b/entities/common/label_test.go
new file mode 100644
index 00000000..206fc4ab
--- /dev/null
+++ b/entities/common/label_test.go
@@ -0,0 +1,35 @@
+package common
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestLabelRGBA(t *testing.T) {
+	rgba := Label("test1").Color()
+	expected := LabelColor{R: 0, G: 150, B: 136, A: 255}
+
+	require.Equal(t, expected, rgba)
+}
+
+func TestLabelRGBASimilar(t *testing.T) {
+	rgba := Label("test2").Color()
+	expected := LabelColor{R: 3, G: 169, B: 244, A: 255}
+
+	require.Equal(t, expected, rgba)
+}
+
+func TestLabelRGBAReverse(t *testing.T) {
+	rgba := Label("tset").Color()
+	expected := LabelColor{R: 63, G: 81, B: 181, A: 255}
+
+	require.Equal(t, expected, rgba)
+}
+
+func TestLabelRGBAEqual(t *testing.T) {
+	color1 := Label("test").Color()
+	color2 := Label("test").Color()
+
+	require.Equal(t, color1, color2)
+}