feat: resolve attachment user through cfw-auth binding

Co-Authored-By: Claude <noreply@anthropic.com>

src/auth-session.ts

@@ -0,0 +1,37 @@
+import type { Env } from "./env";
+import { HttpProblem } from "./problem";
+
+export interface CurrentUser {
+  id: string;
+  email?: string;
+}
+
+interface BetterAuthSessionResponse {
+  user?: {
+    id?: unknown;
+    email?: unknown;
+  };
+}
+
+export async function resolveCurrentUser(request: Request, env: Env): Promise<CurrentUser> {
+  const sessionRequest = new Request("https://cfw-auth.internal/api/auth/get-session", {
+    method: "GET",
+    headers: request.headers,
+  });
+
+  const response = await env.AUTH.fetch(sessionRequest);
+  if (!response.ok) {
+    throw new HttpProblem(401, "authentication-required", "Authentication required");
+  }
+
+  const body = (await response.json()) as BetterAuthSessionResponse | null;
+  const id = body?.user?.id;
+  if (typeof id !== "string" || id.length === 0) {
+    throw new HttpProblem(401, "authentication-required", "Authentication required");
+  }
+
+  return {
+    id,
+    email: typeof body?.user?.email === "string" ? body.user.email : undefined,
+  };
+}

src/problem.ts

@@ -0,0 +1,33 @@
+export class HttpProblem extends Error {
+  constructor(
+    readonly status: number,
+    readonly code: string,
+    message: string,
+    readonly detail: Record<string, unknown> = {},
+  ) {
+    super(message);
+  }
+}
+
+export function problemResponse(error: unknown): Response {
+  const problem =
+    error instanceof HttpProblem
+      ? error
+      : new HttpProblem(500, "internal-error", "Internal server error");
+
+  return Response.json(
+    {
+      type: `https://cfw-attachment.bowong.cc/problems/${problem.code}`,
+      title: problem.message,
+      status: problem.status,
+      detail: problem.detail,
+      code: problem.code,
+    },
+    {
+      status: problem.status,
+      headers: {
+        "content-type": "application/problem+json",
+      },
+    },
+  );
+}

tests/auth-session.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it, vi } from "vitest";
+import { resolveCurrentUser } from "../src/auth-session";
+import type { Env } from "../src/env";
+
+function envWithAuth(response: Response): Env {
+  return {
+    AUTH: { fetch: vi.fn().mockResolvedValue(response) },
+    DB: {} as D1Database,
+    ATTACHMENTS: {} as R2Bucket,
+  };
+}
+
+describe("resolveCurrentUser", () => {
+  it("returns the Better Auth user id from cfw-auth", async () => {
+    const env = envWithAuth(Response.json({ user: { id: "user_123", email: "a@example.com" } }));
+
+    await expect(resolveCurrentUser(new Request("https://attachment.local/api/attachments"), env))
+      .resolves.toEqual({ id: "user_123", email: "a@example.com" });
+  });
+
+  it("throws authentication-required when cfw-auth has no session", async () => {
+    const env = envWithAuth(Response.json(null));
+
+    await expect(resolveCurrentUser(new Request("https://attachment.local/api/attachments"), env))
+      .rejects.toMatchObject({ status: 401, code: "authentication-required" });
+  });
+});