feat(web): add ResolvedTheme types, FALLBACK_THEME, and color scheme helpers (ATB-53)

apps/web/src/lib/__tests__/theme-resolution.test.ts

···
+import { describe, it, expect } from "vitest";
+import {
+  detectColorScheme,
+  parseRkeyFromUri,
+  FALLBACK_THEME,
+} from "../theme-resolution.js";
+
+describe("detectColorScheme", () => {
+  it("returns 'light' by default when no cookie or hint", () => {
+    expect(detectColorScheme(undefined, undefined)).toBe("light");
+  });
+
+  it("reads atbb-color-scheme=dark from cookie", () => {
+    expect(detectColorScheme("atbb-color-scheme=dark; other=1", undefined)).toBe("dark");
+  });
+
+  it("reads atbb-color-scheme=light from cookie", () => {
+    expect(detectColorScheme("atbb-color-scheme=light", undefined)).toBe("light");
+  });
+
+  it("prefers cookie over client hint", () => {
+    expect(detectColorScheme("atbb-color-scheme=light", "dark")).toBe("light");
+  });
+
+  it("falls back to client hint when no cookie", () => {
+    expect(detectColorScheme(undefined, "dark")).toBe("dark");
+  });
+
+  it("ignores unrecognized hint values and returns 'light'", () => {
+    expect(detectColorScheme(undefined, "no-preference")).toBe("light");
+  });
+});
+
+describe("parseRkeyFromUri", () => {
+  it("extracts rkey from valid AT URI", () => {
+    expect(
+      parseRkeyFromUri("at://did:plc:abc123/space.atbb.forum.theme/3lblthemeabc")
+    ).toBe("3lblthemeabc");
+  });
+
+  it("returns null for URI with no rkey segment", () => {
+    expect(parseRkeyFromUri("at://did:plc:abc123/space.atbb.forum.theme")).toBeNull();
+  });
+
+  it("returns null for malformed URI", () => {
+    expect(parseRkeyFromUri("not-a-uri")).toBeNull();
+  });
+
+  it("returns null for empty string", () => {
+    expect(parseRkeyFromUri("")).toBeNull();
+  });
+});
+
+describe("FALLBACK_THEME", () => {
+  it("uses neobrutal-light tokens", () => {
+    expect(FALLBACK_THEME.tokens["color-bg"]).toBe("#f5f0e8");
+    expect(FALLBACK_THEME.tokens["color-primary"]).toBe("#ff5c00");
+  });
+
+  it("has light colorScheme", () => {
+    expect(FALLBACK_THEME.colorScheme).toBe("light");
+  });
+
+  it("includes Google Fonts URL for Space Grotesk", () => {
+    expect(FALLBACK_THEME.fontUrls).toEqual(
+      expect.arrayContaining([expect.stringContaining("Space+Grotesk")])
+    );
+  });
+
+  it("has null cssOverrides", () => {
+    expect(FALLBACK_THEME.cssOverrides).toBeNull();
+  });
+});

apps/web/src/lib/theme-resolution.ts

···
+import neobrutalLight from "../styles/presets/neobrutal-light.json" with { type: "json" };
+
+export type ResolvedTheme = {
+  tokens: Record<string, string>;
+  cssOverrides: string | null;
+  fontUrls: string[] | null;
+  colorScheme: "light" | "dark";
+};
+
+/** Hono app environment type — used by middleware and all route factories. */
+export type WebAppEnv = {
+  Variables: { theme: ResolvedTheme };
+};
+
+/** Hardcoded fallback used when theme policy is missing or resolution fails. */
+export const FALLBACK_THEME: ResolvedTheme = {
+  tokens: neobrutalLight as Record<string, string>,
+  cssOverrides: null,
+  fontUrls: [
+    "https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;700&display=swap",
+  ],
+  colorScheme: "light",
+};
+
+/**
+ * Detects the user's preferred color scheme.
+ * Priority: atbb-color-scheme cookie → Sec-CH-Prefers-Color-Scheme hint → "light".
+ */
+export function detectColorScheme(
+  cookieHeader: string | undefined,
+  hint: string | undefined
+): "light" | "dark" {
+  const match = cookieHeader?.match(/atbb-color-scheme=(light|dark)/);
+  if (match) return match[1] as "light" | "dark";
+  if (hint === "dark") return "dark";
+  return "light";
+}
+
+/**
+ * Extracts the rkey segment from an AT URI.
+ * Example: "at://did:plc:abc/space.atbb.forum.theme/rkey123" → "rkey123"
+ */
+export function parseRkeyFromUri(atUri: string): string | null {
+  // Format: at://<did>/<collection>/<rkey>
+  // Split gives: ["at:", "", "<did>", "<collection>", "<rkey>"]
+  const parts = atUri.split("/");
+  if (parts.length < 5) return null;
+  return parts[4] ?? null;
+}