add readableColor

src/utils/Text.test.ts

@@ -82,4 +82,31 @@ describe("Text", () => {
 			expect(Text.display(undefined)).toBe("");
 		});
 	});
+
+	describe("readableColor", () => {
+		it("should return #FFF for dark backgrounds", () => {
+			expect(Text.readableColor("#000")).toBe("#FFF");
+			expect(Text.readableColor("#123456")).toBe("#FFF");
+		});
+
+		it("should return #111 for light backgrounds", () => {
+			expect(Text.readableColor("#FFF")).toBe("#111");
+			expect(Text.readableColor("#f5f5f5")).toBe("#111");
+		});
+
+		it("should use threshold at luminance 186", () => {
+			expect(Text.readableColor("#BABABA")).toBe("#111");
+			expect(Text.readableColor("#B9B9B9")).toBe("#FFF");
+		});
+
+		it("should trim whitespace and accept mixed case hex", () => {
+			expect(Text.readableColor("  #AbC  ")).toBe("#FFF");
+		});
+
+		it("should return #111 for invalid colors", () => {
+			expect(Text.readableColor("red")).toBe("#111");
+			expect(Text.readableColor("#12")).toBe("#111");
+			expect(Text.readableColor("#GGGGGG")).toBe("#111");
+		});
+	});
 });