Refactor (packages/ui/src/theme/color.ts): Extract RGB gamut check

packages/ui/src/theme/color.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, test } from "bun:test"
+import { fitOklch, oklchToRgb } from "./color"
+
+describe("fitOklch", () => {
+  test("keeps an in-gamut color unchanged", () => {
+    const color = { l: 0.5, c: 0, h: 0 }
+
+    expect(fitOklch(color)).toEqual(color)
+  })
+
+  test("reduces an out-of-gamut color until its RGB values are in gamut", () => {
+    const result = fitOklch({ l: 0.5, c: 0.5, h: 0 })
+    const rgb = oklchToRgb(result)
+
+    expect(result.c).toBeLessThan(0.5)
+    expect(Math.min(rgb.r, rgb.g, rgb.b)).toBeGreaterThanOrEqual(0)
+    expect(Math.max(rgb.r, rgb.g, rgb.b)).toBeLessThanOrEqual(1)
+  })
+})

packages/ui/src/theme/color.ts

@@ -100,6 +100,10 @@ export function hexToOklch(hex: HexColor): OklchColor {
   return rgbToOklch(r, g, b)
 }
 
+function isRgbInGamut(rgb: { r: number; g: number; b: number }) {
+  return Math.min(rgb.r, rgb.g, rgb.b) >= 0 && Math.max(rgb.r, rgb.g, rgb.b) <= 1
+}
+
 export function fitOklch(oklch: OklchColor): OklchColor {
   const base = {
     l: clamp(oklch.l, 0, 1),
@@ -117,7 +121,7 @@ export function fitOklch(oklch: OklchColor): OklchColor {
     c *= 0.9
     const next = { ...base, c }
     const out = oklchToRgb(next)
-    if (out.r >= 0 && out.r <= 1 && out.g >= 0 && out.g <= 1 && out.b >= 0 && out.b <= 1) {
+        if (isRgbInGamut(out)) {
       return next
     }
   }