import assert from "node:assert/strict";
import { test } from "node:test";

import {
  buildStreamingResponseHeaders,
  isNextMiddlewareControlHeader,
  stripNextMiddlewareControlHeaders,
} from "@omniroute/open-sse/handlers/chatCore/responseHeaders.ts";

// Regression guard for issue #5849:
// Providers hosted behind a Next.js middleware (e.g. synthetic.new) leak Next's
// internal `x-middleware-*` control headers on a successful 200 response.
// Forwarding `x-middleware-rewrite` verbatim from an App Router route handler
// makes Next 16 throw `NextResponse.rewrite() was used in a app route handler`
// and return 500. Both proxy paths (streaming + JSON) must strip the family.

const MIDDLEWARE_HEADERS: [string, string][] = [
  ["x-middleware-rewrite", "/internal/rewrite"],
  ["x-middleware-next", "1"],
  ["x-middleware-override-headers", "x-foo"],
  ["x-middleware-set-cookie", "a=b"],
  ["x-middleware-request-foo", "bar"],
];

test("isNextMiddlewareControlHeader matches the whole x-middleware-* family (case-insensitive)", () => {
  for (const [name] of MIDDLEWARE_HEADERS) {
    assert.equal(isNextMiddlewareControlHeader(name), true, name);
    assert.equal(isNextMiddlewareControlHeader(name.toUpperCase()), true, name);
  }
  assert.equal(isNextMiddlewareControlHeader("x-request-id"), false);
  assert.equal(isNextMiddlewareControlHeader("content-type"), false);
});

test("streaming path: buildStreamingResponseHeaders strips x-middleware-* and preserves normal headers", () => {
  const upstream = new Headers();
  for (const [k, v] of MIDDLEWARE_HEADERS) upstream.append(k, v);
  upstream.append("x-request-id", "req-123");

  const out = buildStreamingResponseHeaders(upstream, {});

  const lowerKeys = Object.keys(out).map((k) => k.toLowerCase());
  for (const [name] of MIDDLEWARE_HEADERS) {
    assert.ok(
      !lowerKeys.includes(name.toLowerCase()),
      `expected ${name} to be stripped, got: ${lowerKeys.join(", ")}`
    );
  }
  // Normal upstream header preserved.
  const requestIdKey = Object.keys(out).find((k) => k.toLowerCase() === "x-request-id");
  assert.ok(requestIdKey, "x-request-id must be preserved");
  assert.equal(out[requestIdKey as string], "req-123");
});

test("non-streaming JSON path: stripNextMiddlewareControlHeaders removes the family, keeps the rest", () => {
  const headers = new Headers();
  for (const [k, v] of MIDDLEWARE_HEADERS) headers.append(k, v);
  headers.append("x-request-id", "req-456");
  headers.append("content-type", "application/json");

  stripNextMiddlewareControlHeaders(headers);

  for (const [name] of MIDDLEWARE_HEADERS) {
    assert.equal(headers.get(name), null, `${name} must be stripped`);
  }
  assert.equal(headers.get("x-request-id"), "req-456");
  assert.equal(headers.get("content-type"), "application/json");
});