feat: add server-side deckyvault.xyz domain block middleware (Task 3)

lib/api/__tests__/domain-block-api.test.ts

@@ -0,0 +1,114 @@
+import { describe, it, expect } from "vitest"
+import { Elysia } from "elysia"
+import { isDeckyVaultEmail, DOMAIN_BLOCK_ERROR } from "@/lib/auth/domain-block"
+
+/**
+ * The domain-block onBeforeHandle handler – mirrors the logic
+ * wired into the auth group in lib/api/app.ts.  Tested in isolation
+ * here so we don't need to stand up the full app / DB.
+ */
+const domainBlockOnBeforeHandle = async ({
+  request,
+  set,
+}: {
+  request: Request
+  set: { status: number }
+}) => {
+  const url = new URL(request.url)
+  const isSignUp =
+    url.pathname === "/api/auth/sign-up/email" &&
+    request.method === "POST"
+
+  if (!isSignUp) return
+
+  if (process.env.NODE_ENV !== "development") {
+    try {
+      const cloned = request.clone()
+      const body = await cloned.json()
+      if (isDeckyVaultEmail(body.email)) {
+        set.status = 400
+        return { error: DOMAIN_BLOCK_ERROR }
+      }
+    } catch {
+      // Malformed body — let Better Auth reject it downstream
+    }
+  }
+}
+
+describe("domain block middleware", () => {
+  it("blocks POST /api/auth/sign-up/email with @deckyvault.xyz email", async () => {
+    const app = new Elysia()
+      .onBeforeHandle(domainBlockOnBeforeHandle)
+      .post("/api/auth/sign-up/email", () => ({
+        success: "should not reach this",
+      }))
+
+    const res = await app.handle(
+      new Request("http://localhost:3000/api/auth/sign-up/email", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          email: "bad@deckyvault.xyz",
+          password: "abcdefghij",
+          name: "Test",
+        }),
+      }),
+    )
+
+    expect(res.status).toBe(400)
+    const body = await res.json()
+    expect(body.error).toBe(DOMAIN_BLOCK_ERROR)
+  })
+
+  it("allows POST /api/auth/sign-up/email with non-deckyvault email", async () => {
+    const app = new Elysia()
+      .onBeforeHandle(domainBlockOnBeforeHandle)
+      .post("/api/auth/sign-up/email", () => ({
+        success: true,
+      }))
+
+    const res = await app.handle(
+      new Request("http://localhost:3000/api/auth/sign-up/email", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          email: "good@gmail.com",
+          password: "abcdefghij",
+          name: "Test",
+        }),
+      }),
+    )
+
+    expect(res.status).toBe(200)
+  })
+
+  it("ignores non-sign-up routes (GET /api/auth/something)", async () => {
+    const app = new Elysia()
+      .onBeforeHandle(domainBlockOnBeforeHandle)
+      .get("/api/auth/something", () => ({ ok: true }))
+
+    const res = await app.handle(
+      new Request("http://localhost:3000/api/auth/something"),
+    )
+
+    expect(res.status).toBe(200)
+    const body = await res.json()
+    expect(body.ok).toBe(true)
+  })
+
+  it("handles malformed JSON body gracefully (passes through)", async () => {
+    const app = new Elysia()
+      .onBeforeHandle(domainBlockOnBeforeHandle)
+      .post("/api/auth/sign-up/email", () => ({ success: true }))
+
+    const res = await app.handle(
+      new Request("http://localhost:3000/api/auth/sign-up/email", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: "not-valid-json",
+      }),
+    )
+
+    expect(res.status).toBe(200)
+  })
+})