gods-eye-view/src/data/gbfsProxy.test.mjs

import { test } from 'node:test';
import assert from 'node:assert/strict';
import {
  GBFS_CLIENT_IDENTIFIER,
  GBFS_MAX_BODY_BYTES,
  fetchGbfsUpstream,
} from '../../server/providers/gbfs.js';

const STATION_URL = 'https://gbfs.lyft.com/gbfs/2.3/bay/en/station_status.json';
const STATION_BODY = '{"data":{"stations":[]}}';

/**
 * A Response whose body streams `chunk` forever until the reader cancels it.
 * A zero high-water mark keeps the stream from pulling eagerly at construction,
 * so `pulls()` counts only the chunks a reader actually asked for.
 */
function endlessResponse(chunk, onCancel) {
  let pulls = 0;
  const stream = new ReadableStream(
    {
      pull(controller) {
        pulls += 1;
        controller.enqueue(chunk);
      },
      cancel: onCancel,
    },
    { highWaterMark: 0 },
  );
  return {
    response: new Response(stream, { status: 200 }),
    pulls: () => pulls,
  };
}

test('GBFS upstream fetch passes a direct 200 through unchanged', async () => {
  let observedOptions = null;
  const result = await fetchGbfsUpstream(STATION_URL, {
    fetchImpl: async (_url, options) => {
      observedOptions = options;
      return new Response(STATION_BODY, {
        status: 200,
        headers: { 'Content-Type': 'application/json; charset=utf-8' },
      });
    },
  });

  assert.equal(
    observedOptions.redirect,
    'manual',
    'fetch must not follow redirects on its own',
  );
  assert.ok(observedOptions.signal instanceof AbortSignal);
  assert.deepEqual(result, {
    status: 200,
    contentType: 'application/json; charset=utf-8',
    body: STATION_BODY,
  });
});

test('GBFS upstream fetch names the app in the Client-Identifier header', async () => {
  let observedHeaders = null;
  await fetchGbfsUpstream(
    'https://gbfs.urbansharing.com/oslobysykkel.no/station_status.json',
    {
      fetchImpl: async (_url, options) => {
        observedHeaders = options.headers;
        return new Response(STATION_BODY, { status: 200 });
      },
    },
  );
  assert.equal(GBFS_CLIENT_IDENTIFIER, 'gods-eye-view');
  assert.equal(observedHeaders['Client-Identifier'], GBFS_CLIENT_IDENTIFIER);
});

test('GBFS upstream fetch adds ET-Client-Name for Entur and only for Entur', async () => {
  const headersFor = async (url) => {
    let observed = null;
    await fetchGbfsUpstream(url, {
      fetchImpl: async (_url, options) => {
        observed = options.headers;
        return new Response(STATION_BODY, { status: 200 });
      },
    });
    return observed;
  };
  const entur = await headersFor(
    'https://api.entur.io/mobility/v2/gbfs/v2/kolumbusbysykkel/station_status',
  );
  assert.equal(entur['ET-Client-Name'], 'gods-eye-view-bikeshare');
  assert.equal(entur['Client-Identifier'], GBFS_CLIENT_IDENTIFIER);
  const lyft = await headersFor(STATION_URL);
  assert.equal(lyft['ET-Client-Name'], undefined);
});

test('GBFS upstream fetch forwards a non-redirect error status for the middleware to relay', async () => {
  const result = await fetchGbfsUpstream(STATION_URL, {
    fetchImpl: async () => new Response(null, { status: 404 }),
  });
  assert.equal(result.status, 404);
  assert.equal(
    result.contentType,
    'application/json',
    'a missing upstream content type defaults to JSON',
  );
  assert.equal(result.body, '');
});

test('GBFS upstream fetch rejects every redirect status and never fetches the target', async () => {
  for (const status of [301, 302, 303, 307, 308]) {
    let calls = 0;
    await assert.rejects(
      fetchGbfsUpstream(STATION_URL, {
        fetchImpl: async () => {
          calls += 1;
          return new Response('moved', {
            status,
            headers: {
              Location: 'https://attacker.example/station_status.json',
            },
          });
        },
      }),
      (error) =>
        error?.code === 'GBFS_REDIRECT' &&
        error.redirectHost === 'attacker.example',
      `status ${status} must be refused`,
    );
    assert.equal(
      calls,
      1,
      `status ${status}: the redirect target must not be requested`,
    );
  }
});

test('GBFS upstream fetch names the host of a relative redirect', async () => {
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, {
      fetchImpl: async () =>
        new Response(null, {
          status: 302,
          headers: { Location: '/v2/station_status.json' },
        }),
    }),
    (error) =>
      error?.code === 'GBFS_REDIRECT' && error.redirectHost === 'gbfs.lyft.com',
  );
});

test('GBFS upstream fetch rejects an oversized Content-Length before reading the body', async () => {
  const { response, pulls } = endlessResponse(new Uint8Array(1024));
  response.headers.set('Content-Length', String(GBFS_MAX_BODY_BYTES + 1));
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, { fetchImpl: async () => response }),
    (error) => error?.code === 'RESPONSE_TOO_LARGE',
  );
  assert.equal(
    pulls(),
    0,
    'the body must not be read when the declared length already exceeds the cap',
  );
});

test('GBFS upstream fetch cancels a length-less body the moment it passes the cap', async () => {
  let cancelled = false;
  const chunk = new Uint8Array(1024);
  const { response, pulls } = endlessResponse(chunk, () => {
    cancelled = true;
  });
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, {
      fetchImpl: async () => response,
      maxBytes: 4 * chunk.byteLength,
    }),
    (error) => error?.code === 'RESPONSE_TOO_LARGE',
  );
  assert.equal(
    cancelled,
    true,
    'the upstream stream must be cancelled, not drained',
  );
  assert.ok(
    pulls() <= 8,
    `only a few chunks may be read past the cap, saw ${pulls()}`,
  );
});

test('GBFS upstream fetch measures the cap in bytes and accepts a body exactly at it', async () => {
  const body = 'é'.repeat(64);
  const result = await fetchGbfsUpstream(STATION_URL, {
    fetchImpl: async () => new Response(body, { status: 200 }),
    maxBytes: Buffer.byteLength(body),
  });
  assert.equal(result.body, body);
  assert.equal(GBFS_MAX_BODY_BYTES, 5 * 1024 * 1024);
});

test('GBFS upstream fetch aborts a stalled connection with the timeout signal', async () => {
  const startedAt = Date.now();
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, {
      timeoutMs: 20,
      fetchImpl: (_url, options) =>
        new Promise((_resolve, reject) => {
          options.signal.addEventListener(
            'abort',
            () => reject(options.signal.reason),
            { once: true },
          );
        }),
    }),
    (error) => error?.name === 'AbortError',
  );
  assert.ok(Date.now() - startedAt < 500, 'the timeout must settle promptly');
});

test('GBFS cancels an oversized declared body without pulling it', async () => {
  let cancelled = false;
  const { response, pulls } = endlessResponse(new Uint8Array(1), () => {
    cancelled = true;
  });
  response.headers.set('Content-Length', '100');
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, {
      maxBytes: 10,
      fetchImpl: async () => response,
    }),
    { code: 'RESPONSE_TOO_LARGE' },
  );
  assert.equal(cancelled, true);
  assert.equal(pulls(), 0);
});

test('GBFS deadline includes a stalled body after successful headers', async () => {
  let cancelled = false;
  let signal;
  const response = new Response(
    new ReadableStream({
      pull() {},
      cancel() {
        cancelled = true;
      },
    }),
  );
  await assert.rejects(
    fetchGbfsUpstream(STATION_URL, {
      timeoutMs: 20,
      fetchImpl: async (_url, options) => {
        signal = options.signal;
        return response;
      },
    }),
    { name: 'AbortError' },
  );
  assert.equal(signal.aborted, true);
  assert.equal(cancelled, true);
  assert.equal(response.body.locked, false);
});

test('GBFS rejects redirects and caps bodies through both server hooks', async () => {
  const { gbfsProxy } = await import('../../server/providers/gbfs.js');
  const originalFetch = globalThis.fetch;
  try {
    for (const hook of ['configureServer', 'configurePreviewServer']) {
      let handler;
      gbfsProxy()[hook]({
        middlewares: {
          use(path, callback) {
            assert.equal(path, '/api/gbfs');
            handler = callback;
          },
        },
      });
      for (const response of [
        new Response(null, { status: 302 }),
        new Response('x', {
          headers: { 'Content-Length': String(GBFS_MAX_BODY_BYTES + 1) },
        }),
        new Response(STATION_BODY),
      ]) {
        const expectedStatus =
          response.status === 302 || response.headers.has('content-length')
            ? 502
            : 200;
        globalThis.fetch = async () => response;
        let status, body;
        await handler(
          { method: 'GET', url: '/' + encodeURIComponent(STATION_URL) },
          {
            writeHead(code) {
              status = code;
            },
            end(value) {
              body = value;
            },
          },
        );
        assert.equal(status, expectedStatus);
        if (status === 200) assert.equal(body, STATION_BODY);
        else assert.equal(typeof JSON.parse(body).error, 'string');
      }
    }
  } finally {
    globalThis.fetch = originalFetch;
  }
});