feat: add @tower/config package with env validation

packages/config/src/index.test.ts

@@ -0,0 +1,40 @@
+import { validateEnv } from './index';
+
+const validEnv = {
+  NODE_ENV: 'development',
+  DATABASE_URL: 'postgresql://tower:tower_dev@localhost:5432/tower_dev',
+  REDIS_URL: 'redis://localhost:6379',
+  JWT_SECRET: 'a_super_secret_key_that_is_at_least_32_chars_long',
+} as unknown as NodeJS.ProcessEnv;
+
+describe('validateEnv', () => {
+  it('returns parsed config for valid env', () => {
+    const result = validateEnv(validEnv);
+    expect(result.NODE_ENV).toBe('development');
+    expect(result.API_PORT).toBe(3001);
+  });
+
+  it('applies default API_PORT of 3001 when not set', () => {
+    const result = validateEnv(validEnv);
+    expect(result.API_PORT).toBe(3001);
+  });
+
+  it('throws when DATABASE_URL is missing', () => {
+    const { DATABASE_URL, ...withoutDb } = validEnv as Record<string, string>;
+    expect(() =>
+      validateEnv(withoutDb as unknown as NodeJS.ProcessEnv),
+    ).toThrow('Invalid environment variables');
+  });
+
+  it('throws when JWT_SECRET is shorter than 32 chars', () => {
+    expect(() =>
+      validateEnv({ ...validEnv, JWT_SECRET: 'tooshort' } as unknown as NodeJS.ProcessEnv),
+    ).toThrow('Invalid environment variables');
+  });
+
+  it('throws when DATABASE_URL is not a valid URL', () => {
+    expect(() =>
+      validateEnv({ ...validEnv, DATABASE_URL: 'not-a-url' } as unknown as NodeJS.ProcessEnv),
+    ).toThrow('Invalid environment variables');
+  });
+});