From 91e137a013e7adb3929cdd50d4641e4e4317c5b5 Mon Sep 17 00:00:00 2001
From: hsiegeln <37154749+hsiegeln@users.noreply.github.com>
Date: Wed, 18 Mar 2026 09:09:16 +0100
Subject: [PATCH] feat: hashColor utility with FNV-1a for deterministic
 badge/avatar colors

---
 src/design-system/utils/hashColor.test.ts | 50 +++++++++++++++++++++++
 src/design-system/utils/hashColor.ts      | 32 +++++++++++++++
 2 files changed, 82 insertions(+)
 create mode 100644 src/design-system/utils/hashColor.test.ts
 create mode 100644 src/design-system/utils/hashColor.ts

diff --git a/src/design-system/utils/hashColor.test.ts b/src/design-system/utils/hashColor.test.ts
new file mode 100644
index 0000000..c68313a
--- /dev/null
+++ b/src/design-system/utils/hashColor.test.ts
@@ -0,0 +1,50 @@
+import { describe, it, expect } from 'vitest'
+import { hashColor, fnv1a } from './hashColor'
+
+describe('fnv1a', () => {
+  it('returns a number for any string', () => {
+    expect(typeof fnv1a('test')).toBe('number')
+  })
+
+  it('returns consistent hash for same input', () => {
+    expect(fnv1a('order-service')).toBe(fnv1a('order-service'))
+  })
+
+  it('returns different hashes for different inputs', () => {
+    expect(fnv1a('order-service')).not.toBe(fnv1a('payment-service'))
+  })
+})
+
+describe('hashColor', () => {
+  it('returns bg, text, and border properties', () => {
+    const result = hashColor('test')
+    expect(result).toHaveProperty('bg')
+    expect(result).toHaveProperty('text')
+    expect(result).toHaveProperty('border')
+  })
+
+  it('returns HSL color strings', () => {
+    const result = hashColor('order-service')
+    expect(result.bg).toMatch(/^hsl\(\d+,\s*\d+%,\s*\d+%\)$/)
+    expect(result.text).toMatch(/^hsl\(\d+,\s*\d+%,\s*\d+%\)$/)
+    expect(result.border).toMatch(/^hsl\(\d+,\s*\d+%,\s*\d+%\)$/)
+  })
+
+  it('returns consistent colors for same name', () => {
+    const a = hashColor('VIEWER')
+    const b = hashColor('VIEWER')
+    expect(a).toEqual(b)
+  })
+
+  it('returns different hues for different names', () => {
+    const a = hashColor('VIEWER')
+    const b = hashColor('OPERATOR')
+    expect(a.bg).not.toBe(b.bg)
+  })
+
+  it('accepts dark mode parameter', () => {
+    const light = hashColor('test', 'light')
+    const dark = hashColor('test', 'dark')
+    expect(light.bg).not.toBe(dark.bg)
+  })
+})
diff --git a/src/design-system/utils/hashColor.ts b/src/design-system/utils/hashColor.ts
new file mode 100644
index 0000000..0fc6f99
--- /dev/null
+++ b/src/design-system/utils/hashColor.ts
@@ -0,0 +1,32 @@
+const FNV_OFFSET = 2166136261
+const FNV_PRIME = 16777619
+
+export function fnv1a(str: string): number {
+  let hash = FNV_OFFSET
+  for (let i = 0; i < str.length; i++) {
+    hash ^= str.charCodeAt(i)
+    hash = Math.imul(hash, FNV_PRIME)
+  }
+  return hash >>> 0
+}
+
+export function hashColor(
+  name: string,
+  theme: 'light' | 'dark' = 'light',
+): { bg: string; text: string; border: string } {
+  const hue = fnv1a(name) % 360
+
+  if (theme === 'dark') {
+    return {
+      bg: `hsl(${hue}, 35%, 20%)`,
+      text: `hsl(${hue}, 45%, 75%)`,
+      border: `hsl(${hue}, 30%, 30%)`,
+    }
+  }
+
+  return {
+    bg: `hsl(${hue}, 45%, 92%)`,
+    text: `hsl(${hue}, 55%, 35%)`,
+    border: `hsl(${hue}, 35%, 82%)`,
+  }
+}