import { readFileSync } from "node:fs";
import { fileURLToPath } from "node:url";
import path from "node:path";

import { describe, expect, test } from "vitest";

// Source-level checks: importing entry.server.tsx pulls in the Sentry SDK
// and the React Router runtime, which is heavier than this test needs.
// Reading the file as text is enough to enforce the asset-CDN cache contract.
// See docs/improvement-plan/03-scaling-infrastructure/asset-cdn.md.
const entrySource = readFileSync(
  path.join(path.dirname(fileURLToPath(import.meta.url)), "entry.server.tsx"),
  "utf8"
);

describe("entry.server cache-control contract", () => {
  test("sets `no-store` on HTML responses when no loader-provided value exists", () => {
    expect(entrySource).toContain('responseHeaders.set("Content-Type", "text/html")');
    expect(entrySource).toMatch(/if \(!responseHeaders\.has\("Cache-Control"\)\)/);
    expect(entrySource).toContain('responseHeaders.set("Cache-Control", "no-store")');
  });

  test("does not override loader-provided Cache-Control headers", () => {
    // The implementation uses `has()` to opt-in to the default rather than
    // unconditionally setting it — this means a loader returning a
    // `Cache-Control: public, max-age=300` (e.g. a marketing landing page)
    // keeps its value. Drift here would silently break loader-defined
    // caching, so guard it with a structural assertion.
    expect(entrySource).not.toMatch(/responseHeaders\.set\("Cache-Control"[^)]*\);[^!]*responseHeaders\.set\("Cache-Control"/);
  });

  test("sets the cache header before constructing the response", () => {
    const setIndex = entrySource.indexOf('responseHeaders.set("Cache-Control", "no-store")');
    const responseIndex = entrySource.indexOf("new Response(stream", setIndex);
    expect(setIndex).toBeGreaterThan(0);
    expect(responseIndex).toBeGreaterThan(setIndex);
  });
});