feat: add runtime feature overrides

tests/runtime-features.test.ts

@@ -0,0 +1,113 @@
+import { randomUUID } from 'node:crypto';
+import { mkdir, readFile, writeFile } from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+import { afterEach, describe, expect, it } from 'vitest';
+import { clearFeatureOverridesCache, refreshFeatureOverridesCache } from '../src/lib/runtime-features.js';
+import { buildLikesFeatures, buildSearchFeatures } from '../src/lib/twitter-client-features.js';
+
+describe('runtime-features', () => {
+  afterEach(() => {
+    delete process.env.BIRD_FEATURES_JSON;
+    delete process.env.BIRD_FEATURES_CACHE;
+    delete process.env.BIRD_FEATURES_PATH;
+    clearFeatureOverridesCache();
+  });
+
+  it('applies global and set overrides from env json', () => {
+    process.env.BIRD_FEATURES_JSON = JSON.stringify({
+      global: {
+        global_flag: true,
+        ignored: 'nope',
+      },
+      sets: {
+        search: {
+          global_flag: false,
+          search_only: true,
+          bad: 1,
+        },
+        likes: {
+          likes_only: true,
+        },
+      },
+    });
+
+    clearFeatureOverridesCache();
+    const search = buildSearchFeatures();
+    expect(search.global_flag).toBe(false);
+    expect(search.search_only).toBe(true);
+    expect(search.bad).toBeUndefined();
+
+    const likes = buildLikesFeatures();
+    expect(likes.global_flag).toBe(true);
+    expect(likes.likes_only).toBe(true);
+  });
+
+  it('refresh merges defaults with existing cache', async () => {
+    const cacheDir = path.join(os.tmpdir(), `bird-test-${randomUUID()}`);
+    await mkdir(cacheDir, { recursive: true });
+    const cachePath = path.join(cacheDir, 'features.json');
+
+    await writeFile(
+      cachePath,
+      JSON.stringify(
+        {
+          global: {
+            existing_flag: true,
+          },
+          sets: {
+            search: {
+              existing_search: false,
+            },
+          },
+        },
+        null,
+        2,
+      ),
+    );
+
+    process.env.BIRD_FEATURES_PATH = cachePath;
+    await refreshFeatureOverridesCache();
+
+    const raw = await readFile(cachePath, 'utf8');
+    const parsed = JSON.parse(raw) as {
+      global?: Record<string, boolean>;
+      sets?: Record<string, Record<string, boolean>>;
+    };
+
+    expect(parsed.global?.existing_flag).toBe(true);
+    expect(parsed.global?.responsive_web_grok_annotations_enabled).toBe(false);
+    expect(parsed.sets?.search?.existing_search).toBe(false);
+  });
+
+  it('applies overrides from cache file', async () => {
+    const cacheDir = path.join(os.tmpdir(), `bird-test-${randomUUID()}`);
+    await mkdir(cacheDir, { recursive: true });
+    const cachePath = path.join(cacheDir, 'features.json');
+
+    await writeFile(
+      cachePath,
+      JSON.stringify(
+        {
+          global: {
+            file_flag: true,
+          },
+          sets: {
+            search: {
+              file_search: true,
+            },
+          },
+        },
+        null,
+        2,
+      ),
+    );
+
+    process.env.BIRD_FEATURES_PATH = cachePath;
+    clearFeatureOverridesCache();
+
+    const search = buildSearchFeatures();
+    expect(search.file_flag).toBe(true);
+    expect(search.file_search).toBe(true);
+  });
+});