gitea/sidecar/rewrite.test.ts

import { describe, expect, test } from 'bun:test';
import {
  rewriteHtml,
  rewriteLocation,
  rewriteSetCookie,
  rewriteAttributes,
  rewriteAppSubUrl,
  rewriteAssetPaths,
} from './rewrite';

const BASE = '/api/gitea/_web';
const ORIGINS = ['http://localhost:3000', 'https://gitea.officer.dev'];

// Every test here is a way the frame breaks in a manner that looks like Gitea being broken rather than
// the proxy. That is the whole difficulty: the page renders, and then a click, a login or an asset goes
// somewhere Officer knows nothing about.

describe('attributes', () => {
  test('root-absolute href, src and action are prefixed', () => {
    const html = '<a href="/user/login"><img src="/assets/img/logo.svg"><form action="/repo/new">';
    const out = rewriteAttributes(html, BASE);
    expect(out).toContain(`href="${BASE}/user/login"`);
    expect(out).toContain(`src="${BASE}/assets/img/logo.svg"`);
    expect(out).toContain(`action="${BASE}/repo/new"`);
  });

  test('a relative href is already correct and must not be touched', () => {
    expect(rewriteAttributes('<a href="settings">', BASE)).toBe('<a href="settings">');
  });

  test('mailto, data and protocol-relative are left alone', () => {
    const html = '<a href="mailto:a@b.c"><img src="data:image/png;base64,AAA"><script src="//cdn.example/x.js">';
    expect(rewriteAttributes(html, BASE)).toBe(html);
  });

  test('`..` is collapsed before prefixing, or the browser normalises the prefix back off', () => {
    expect(rewriteAttributes('<img src="/../../assets/x.png">', BASE)).toContain(`src="${BASE}/assets/x.png"`);
  });
});

describe('appSubUrl — the line that makes Gitea correct itself', () => {
  test('is filled in, so Gitea client JS builds prefixed URLs natively', () => {
    const html = '<script>window.config = {"appUrl":"http://localhost:3000/","appSubUrl":""};</script>';
    expect(rewriteAppSubUrl(html, BASE)).toContain(`"appSubUrl":"${BASE}"`);
  });

  test('an existing subpath is replaced, not appended to', () => {
    expect(rewriteAppSubUrl('{"appSubUrl":"/git"}', BASE)).toBe(`{"appSubUrl":"${BASE}"}`);
  });

  // The shape Gitea ACTUALLY emits — a JavaScript object literal, unquoted key, single quotes. The first
  // version of this only matched the JSON form, so it silently did nothing on every real page while the
  // attributes around it rewrote perfectly. Taken verbatim from a live response.
  test('the JS object-literal form Gitea really emits', () => {
    const real = "window.config = {\n  appUrl: 'https://gitea.officer.dev/',\n  appSubUrl: '',\n};";
    const out = rewriteAppSubUrl(real, BASE);
    expect(out).toContain(`appSubUrl: '${BASE}'`);
    // The quote style is preserved, or the literal stops parsing.
    expect(out).not.toContain(`appSubUrl: "${BASE}"`);
  });
});

describe('absolute URLs built from ROOT_URL', () => {
  test('the upstream origin becomes the proxy base — these escape to a third-party origin otherwise', () => {
    const out = rewriteHtml('<a href="https://gitea.officer.dev/owner/repo">', BASE, ORIGINS);
    expect(out).toContain(`href="${BASE}/owner/repo"`);
    expect(out).not.toContain('gitea.officer.dev');
  });

  test('the loopback origin is rewritten too, since that is what the sidecar actually fetches', () => {
    expect(rewriteHtml('<a href="http://localhost:3000/explore">', BASE, ORIGINS)).toContain(`${BASE}/explore`);
  });

  test('the JSON-ESCAPED form, which is how appUrl appears in Gitea\'s inline script', () => {
    // `appUrl: 'https:\\/\\/gitea.officer.dev\\/'`. Missed at first, and the failure was quiet: the page
    // rendered fine while every URL Gitea's JS built from appUrl went cross-origin to the real host and
    // came back as its login HTML — so the heatmap reported "Unexpected token '<'" parsing JSON.
    const real = String.raw`appUrl: 'https:\/\/gitea.officer.dev\/',`;
    const out = rewriteHtml(real, BASE, ORIGINS);
    expect(out).toContain(String.raw`'\/api\/gitea\/_web\/'`);
    expect(out).not.toContain('gitea.officer.dev');
  });

  test('an unrelated host is left alone', () => {
    const html = '<a href="https://github.com/some/repo">';
    expect(rewriteHtml(html, BASE, ORIGINS)).toBe(html);
  });
});

describe('redirects — the most visible failure, because the frame just leaves', () => {
  test('a root-absolute Location is prefixed', () => {
    expect(rewriteLocation('/user/login', BASE, ORIGINS)).toBe(`${BASE}/user/login`);
  });

  test('a full URL on the upstream origin is brought back inside', () => {
    expect(rewriteLocation('https://gitea.officer.dev/dashboard', BASE, ORIGINS)).toBe(`${BASE}/dashboard`);
  });

  test('an already-prefixed Location is not prefixed twice', () => {
    expect(rewriteLocation(`${BASE}/dashboard`, BASE, ORIGINS)).toBe(`${BASE}/dashboard`);
  });

  test('an external redirect is left alone — OAuth goes where it goes', () => {
    expect(rewriteLocation('https://accounts.google.com/o/oauth2/auth', BASE, ORIGINS)).toBe(
      'https://accounts.google.com/o/oauth2/auth',
    );
  });
});

describe('asset paths baked into the page before Gitea\'s own code runs', () => {
  test('the JSON-escaped form — the SharedWorker URL that broke the dashboard', () => {
    // Verbatim from a live page. Not an attribute, and its slashes are backslash-escaped, so neither the
    // attribute rewrite nor appSubUrl touches it. Unprefixed, the browser resolves it against the
    // PLATFORM's origin, gets the SPA's index.html, and reports `Unexpected token '<'` from a file that
    // looks like it loaded.
    const real = String.raw`'\/assets\/js\/eventsource.sharedworker.DV1Z2uJv.js',`;
    const out = rewriteAssetPaths(real, BASE);
    expect(out).toContain(String.raw`'\/api\/gitea\/_web\/assets\/js\/eventsource`);
    // The escaping has to match the string it lands in, or the JS stops parsing.
    expect(out).not.toContain(String.raw`\\/api`);
  });

  test('the plain quoted form too', () => {
    expect(rewriteAssetPaths(`x = "/assets/img/logo.svg"`, BASE)).toContain(`"${BASE}/assets/img/logo.svg"`);
  });

  test('leaves a path that is not an asset root alone', () => {
    expect(rewriteAssetPaths(`x = "/user/login"`, BASE)).toBe(`x = "/user/login"`);
  });
});

describe('the origin Gitea declares about itself', () => {
  test('is discovered from window.config, so ROOT_URL needs no second setting', () => {
    // The sidecar only knows where it FETCHES from — usually loopback. The public origin lives in the
    // page, and an unrewritten absolute link on it navigates the frame off to a third-party origin where
    // the session cookie is dropped.
    const html = '<script>window.config={"appUrl":"https://git.example.com/","appSubUrl":""}</script>' +
      '<a href="https://git.example.com/owner/repo">go</a>';
    const out = rewriteHtml(html, BASE, ['http://localhost:3000']);
    expect(out).toContain(`href="${BASE}/owner/repo"`);
    expect(out).not.toContain('git.example.com/owner');
  });

  test('a page without one still rewrites what it was told about', () => {
    expect(rewriteHtml('<a href="http://localhost:3000/x">', BASE, ['http://localhost:3000'])).toContain(
      `href="${BASE}/x"`,
    );
  });
});

describe('cookies', () => {
  test('Path is narrowed to the frame, so Gitea session cookies stay out of the platform API', () => {
    expect(rewriteSetCookie('i_like_gitea=abc; Path=/; HttpOnly', BASE)).toBe(
      `i_like_gitea=abc; Path=${BASE}; HttpOnly`,
    );
  });

  test('a cookie with no Path gets one', () => {
    expect(rewriteSetCookie('csrf=xyz; HttpOnly', BASE)).toBe(`csrf=xyz; HttpOnly; Path=${BASE}`);
  });

  test('Secure is left exactly as Gitea set it — adding it breaks http, removing it weakens https', () => {
    expect(rewriteSetCookie('s=1; Path=/; Secure; SameSite=Lax', BASE)).toContain('Secure');
    expect(rewriteSetCookie('s=1; Path=/', BASE)).not.toContain('Secure');
  });
});