feat: add semantic admin palette

src/lib/theme-contrast.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { contrastRatio, derivePublicForegrounds, readableColor } from "@/lib/theme-contrast";
+import { contrastRatio, deriveAdminPalette, derivePublicForegrounds, readableColor } from "@/lib/theme-contrast";
 import { PRESETS, THEME_COLOR_KEYS } from "@/lib/theme-presets";
 
 describe("contrastRatio", () => {
@@ -76,6 +76,26 @@ describe("readableColor", () => {
   });
 });
 
+describe("deriveAdminPalette", () => {
+  it.each(Object.entries(PRESETS))("keeps admin text readable for %s", (_name, preset) => {
+    for (const palette of [preset.light, preset.dark]) {
+      const admin = deriveAdminPalette(palette);
+      expect(contrastRatio(admin.text, admin.canvas)).toBeGreaterThanOrEqual(4.5);
+      expect(contrastRatio(admin.text, admin.surface)).toBeGreaterThanOrEqual(4.5);
+      expect(contrastRatio(admin.muted, admin.surface)).toBeGreaterThanOrEqual(4.5);
+      expect(contrastRatio(admin.accentForeground, admin.accent)).toBeGreaterThanOrEqual(4.5);
+    }
+  });
+
+  it("does not copy hostile public structural colors into admin surfaces", () => {
+    const admin = deriveAdminPalette({
+      color_background: "#ff00ff", color_surface: "#00ff00", color_primary: "#ffff00",
+    });
+    expect(admin.canvas).not.toBe("#ff00ff");
+    expect(admin.surface).not.toBe("#00ff00");
+  });
+});
+
 describe("derivePublicForegrounds", () => {
   it.each(Object.entries(PRESETS))("makes every semantic pair readable for %s", (_name, preset) => {
     for (const palette of [preset.light, preset.dark]) {

src/lib/theme-contrast.ts

@@ -3,6 +3,58 @@ type Rgb = readonly [number, number, number];
 export type PublicThemeColors = Record<string, string>;
 export interface ContrastPair { name: string; foreground: string; background: string }
 
+export interface AdminPalette {
+  canvas: string;
+  surface: string;
+  surfaceElevated: string;
+  text: string;
+  muted: string;
+  border: string;
+  accent: string;
+  accentText: string;
+  accentForeground: string;
+  success: string;
+  warning: string;
+  error: string;
+  info: string;
+  sidebar: string;
+  sidebarText: string;
+  overlay: string;
+  focusRing: string;
+}
+
+export function deriveAdminPalette(colors: PublicThemeColors): AdminPalette {
+  const publicBackground = colors.color_background ?? "#f8fafc";
+  const blackRatio = contrastRatio("#000000", publicBackground) ?? 21;
+  const whiteRatio = contrastRatio("#ffffff", publicBackground) ?? 1;
+  const dark = whiteRatio > blackRatio;
+  const canvas = dark ? "#0b0f19" : "#f1f5f9";
+  const surface = dark ? "#151b27" : "#ffffff";
+  const surfaceElevated = dark ? "#1e2635" : "#f8fafc";
+  const text = dark ? "#f8fafc" : "#0f172a";
+  const muted = dark ? "#a8b3c7" : "#475569";
+  const accent = colors.color_primary ?? "#f59e0b";
+  return {
+    canvas,
+    surface,
+    surfaceElevated,
+    text: readableColor(text, [canvas, surface, surfaceElevated]),
+    muted: readableColor(muted, [canvas, surface, surfaceElevated]),
+    border: dark ? "#334155" : "#cbd5e1",
+    accent,
+    accentText: readableColor(accent, [canvas, surface, surfaceElevated]),
+    accentForeground: readableColor("#ffffff", [accent]),
+    success: dark ? "#4ade80" : "#15803d",
+    warning: dark ? "#facc15" : "#a16207",
+    error: dark ? "#f87171" : "#b91c1c",
+    info: dark ? "#38bdf8" : "#0369a1",
+    sidebar: dark ? "#101622" : "#172033",
+    sidebarText: "#f8fafc",
+    overlay: "rgba(2, 6, 23, 0.72)",
+    focusRing: accent,
+  };
+}
+
 export function derivePublicForegrounds(c: PublicThemeColors) {
   const value = (key: string, fallback: string) => c[key] ?? fallback;
   const background = value("color_background", "#f8fafc");

src/lib/theme-css.ts

@@ -1,4 +1,4 @@
-import { derivePublicForegrounds, readableColor } from "@/lib/theme-contrast";
+import { deriveAdminPalette, derivePublicForegrounds, readableColor } from "@/lib/theme-contrast";
 import type { ThemePalette } from "@/lib/theme-presets";
 
 const CSS_VARIABLES: Record<keyof ThemePalette, string> = {
@@ -19,6 +19,7 @@ const CSS_VARIABLES: Record<keyof ThemePalette, string> = {
 
 export function themePaletteCss(selector: string, palette: ThemePalette): string {
   const semantic = derivePublicForegrounds(palette);
+  const admin = deriveAdminPalette(palette);
   const declarations = Object.entries(CSS_VARIABLES).map(
     ([key, cssName]) => `--${cssName}:${palette[key as keyof ThemePalette]};`,
   );
@@ -47,6 +48,23 @@ export function themePaletteCss(selector: string, palette: ThemePalette): string
     `--admin-sidebar-text-readable:${semantic.byName.sidebar};`,
     `--admin-sidebar-muted-readable:${semantic.byName.sidebar};`,
     `--admin-input-text-readable:${semantic.byName.input};`,
+    `--admin-canvas:${admin.canvas};`,
+    `--admin-surface:${admin.surface};`,
+    `--admin-surface-elevated:${admin.surfaceElevated};`,
+    `--admin-text:${admin.text};`,
+    `--admin-text-muted:${admin.muted};`,
+    `--admin-border:${admin.border};`,
+    `--admin-accent:${admin.accent};`,
+    `--admin-accent-text:${admin.accentText};`,
+    `--admin-accent-foreground:${admin.accentForeground};`,
+    `--admin-success:${admin.success};`,
+    `--admin-warning:${admin.warning};`,
+    `--admin-error:${admin.error};`,
+    `--admin-info:${admin.info};`,
+    `--admin-sidebar:${admin.sidebar};`,
+    `--admin-sidebar-text:${admin.sidebarText};`,
+    `--admin-overlay:${admin.overlay};`,
+    `--admin-focus-ring:${admin.focusRing};`,
     ...(["success", "warning", "error", "info"] as const).flatMap((status) => [
       `--color-${status}-text-readable:${semantic.byName[`${status}-text`]};`,
       `--color-${status}-foreground-readable:${semantic.byName[`${status}-solid`]};`,