CODE PATTERNS

export async function POST(req: NextRequest) {
  const body = schema.parse(await req.json())
  const result = await service.create(body)
  return NextResponse.json(result)
}

export class ProjectService {
  async create(data: CreateInput): Promise<Project> {
    // ownership check, validation, persist
  }
}

export function ProjectList({ projects }: Props) {
  if (!projects) return <Skeleton />
  if (projects.length === 0) return <Empty />
  return <ul role="list">...</ul>
}

export function withAuth(handler: Handler) {
  return async (req: NextRequest) => {
    const session = await getSession(req)
    if (!session) return unauthorized()
    return handler(req, session)
  }
}

export class ApiError extends Error {
  constructor(
    public code: ErrorCode,
    message: string,
    public status: number = 500
  ) { super(message) }
}

export async function processJob(job: Job) {
  if (await isProcessed(job.id)) return // idempotent
  try { await execute(job) }
  catch { await retry(job) }
}

export function scopedQuery<T>(workspace: string) {
  return db.query<T>()
    .where('workspace_id', workspace)
    // tenant isolation enforced
}

export function GET(req: NextRequest) {
  const stream = new ReadableStream({
    start(controller) {
      const send = (data: string) =>
        controller.enqueue(`data: ${data}\n\n`)
    }
  })
}

type ScriptState = 'loading' | 'ready' | 'error';

function loadScript(src: string) {
  const el = document.createElement('script');
  el.onload = () => state = 'ready';
  el.onerror = () => state = 'error';
}

function useCombobox<T>(options: ComboboxOptions<T>) {
  const [isOpen, setIsOpen] = useState(false)
  const [query, setQuery] = useState("")
  // Two value sources: display vs search
}

const tokenColor = (role) => `var(--vf-color-${role.replace(/[.\s]+/g, '-')})`
// component references SEMANTIC tokens only — never a hex, never a pixel literal
style = { background: tokenColor('accent'), color: tokenColor('text.on-accent') }

export function classify(err: NormalizedError): ErrorCategory {
  if (err.isNetworkError) return 'network'
  if (QUOTA_CODES.has((err.code ?? '').toLowerCase())) return 'quota'
  switch (err.status) { case 402: return 'quota'; case 401: return 'auth'; /* ... */ }
}

export function ProfileScreen() {
  const insets = useSafeAreaInsets()
  const { data, error, loading } = useProfile()
  if (loading) return <ScreenSkeleton />
}

export class OfflineService {
  async read(id: string) {
    return localStore.get(id) ?? await api.fetch(id)
  }
}

class GameLoop {
  tick(dt: number) {
    this.accumulator += dt
    while (this.accumulator >= STEP) {
      this.update(STEP)
    }
  }
}

class StateMachine {
  transition(to: string) {
    this.current.exit()
    this.current = this.states[to]
    this.current.enter()
  }
}

class World {
  createEntity(): number {
    return this.nextId++
  }
  addComponent<T>(entity: number, type: string, data: T) {
    this.stores[type].set(entity, data)
  }
}

interface AdPlatformAdapter {
  createCampaign(config: CampaignConfig): Promise<Campaign>
  getCampaignMetrics(id: string): Promise<Metrics>
  pauseCampaign(id: string): Promise<void>
}

type Cents = number & { __brand: "cents" };
function toCents(dollars: number): Cents {
  return Math.round(dollars * 100) as Cents;
}

class Daemon {
  async start() {
    this.writePid();
    this.startSocket();
    this.scheduleJobs();
    process.on("SIGTERM", () => this.shutdown());
  }
}

interface RevenueAdapter {
  getTransactions(since: Date): Promise<Transaction[]>
  getBalance(): Promise<Cents>
  getSubscriptionMRR(): Promise<Cents>
}

class TokenManager {
  async getToken(): Promise<string> {
    if (this.shouldRefresh()) await this.refresh();
    return this.accessToken;
  }
}

class RateLimiter {
  async acquire(): Promise<void> {
    while (this.tokens <= 0) {
      await this.waitForRefill();
    }
    this.tokens--;
  }
}

// Safe column add: nullable first, backfill, constrain
await db.schema.alterTable('users', (t) => {
  t.string('email_verified').nullable();
});
await batchUpdate('users', setDefault);

const pipeline = new Pipeline([
  extract(source),
  validate(schema),
  transform(normalize),
  load(destination),
]);
await pipeline.run({ checkpoint: true });

const engine = new BacktestEngine(strategy);
const result = await engine.run(historicalData, {
  slippage: 0.001,
  commission: 0.0005,
});
console.log(result.sharpeRatio);

const order = validateOrder({
  symbol: 'BTC/USDT',
  side: 'buy',
  size: 0.1,
}, exchangeRules);
await executor.submit(order);

test('homepage loads and is accessible', async ({ page }) => {
  await page.goto('/');
  await expect(page.getByRole('heading')).toBeVisible();
  const results = await new AxeBuilder({ page }).analyze();
  expect(results.violations).toHaveLength(0);
});

async function browserReview(page: Page) {
  const errors: string[] = [];
  page.on('console', m => {
    if (m.type() === 'error') errors.push(m.text());
  });
  await page.goto('/');
  return { errors, screenshot: await page.screenshot() };
}

interface StablecoinAdapter {
  getBalance(): Promise<BalanceCents>;
  initiateOfframp(amount: Cents): Promise<Transfer>;
  getTransferStatus(id: string): Promise<TransferState>;
}

type BillingCapability =
  | 'FULLY_FUNDABLE'
  | 'MONITORED_ONLY'
  | 'UNSUPPORTED';

interface AdBillingAdapter {
  classifyBilling(): Promise<BillingCapability>;
  getInvoices(): Promise<Invoice[]>;
}

type FundingPlanState =
  | 'DRAFT' | 'APPROVED'
  | 'EXECUTING' | 'SETTLED' | 'FAILED';

interface FundingPlan {
  id: string;
  state: FundingPlanState;
  amountCents: Cents;
  reason: string;
}

interface KongoClientConfig {
  apiKey: string;     // ke_live_ prefix, vault-sourced
  baseUrl?: string;   // Default: https://kongo.io/api/v1
  rateLimitPerMinute?: number;
}

// Pattern 2: sentinel + JSONB tag
await writeSystemAudit(db, {
  action: 'retention.sweep',
  resource_type: 'job',
  resource_id: jobId,
  decisions: { reason: 'scheduled' },
});

// CI step before wrangler/vercel/firebase:
// - run: npx tsx docs/patterns/deploy-preflight.ts ./dist
// Exits non-zero on any hit. Never auto-filters.

await preOrgResolutionScope(async () => {
  const session = await db.query('SELECT org_id FROM sessions WHERE token = $1', [token]);
  return withTenant(session.org_id, () => handler(session));
});

test('writes by org A never appear in reads by org B', async () => {
  await fc.assert(fc.asyncProperty(
    fc.constantFrom(...readEndpoints),
    randomPayload(),
    async (endpoint, payload) => { /* leak check */ },
  ));
});

# Cloudflare Flexible: edge does HTTPS, this hop is HTTP.
# NO `return 301 https://...` here — it would loop.
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
location ^~ /.well-known/acme-challenge/ { root /var/www/acme; try_files $uri =404; }
proxy_set_header X-Forwarded-Proto https;

# DEPLOY_URL=https://example.com bash docs/patterns/post-deploy-probe.sh
# Probes a denylist against the LIVE deploy. Exits non-zero on any 200.
# LEAK  200  -> https://example.com/.env    ← rollback and fix the surface
# ok    404  -> https://example.com/.git/config

@pytest_asyncio.fixture
async def db_as_app(db):
    await db.execute("SAVEPOINT rls_test")
    try:
        await db.execute(f"SET LOCAL ROLE {APP_ROLE_NAME}")
        yield db
    finally:
        await db.execute("ROLLBACK TO SAVEPOINT rls_test")

@pytest.mark.parametrize("form", POSITIVE_FORMS)
def test_sentinel_catches_fail_open_form(form: str) -> None:
    """Every known fail-open variant must trip the sentinel."""
    assert policy_is_fail_open(form), \
        f"SENTINEL GAP: form did not trip — '{form}'"

async function agentLoop(messages: Message[]) {
  for (let i = 0; i < MAX_ITERATIONS; i++) {
    const response = await model.complete(messages);
    if (response.stopReason === 'end_turn') return;
    // Execute tool calls, append results
  }
}

async function classify(input: string) {
  const { label, confidence } = await model.classify(input);
  if (confidence > 0.9) return autoAct(label);
  if (confidence > 0.7) return softAct(label);
  return humanReview(input);
}

const intents = ['create_order', 'check_status', 'cancel'] as const;

async function route(input: string) {
  const intent = await detectIntent(input, intents);
  return handlers[intent](input);
}

const template = new PromptTemplate({
  version: '1.2',
  text: 'Classify this {{category}}: {{input}}',
  variables: ['category', 'input'],
});

const suite = new EvalSuite('classifier-v2', [
  { input: 'refund please', expected: 'refund' },
  { input: 'where is my order', expected: 'status' },
]);
await suite.run(classifyFn);

const searchTool = defineTool({
  name: 'search',
  description: 'Search the knowledge base',
  parameters: z.object({ query: z.string() }),
  execute: async ({ query }) => search(query),
});

const AUTHORITY: InstructionTextControl = {
  type: 'instruction',
  text: 'Only execute approved commands.',
  defeatedBy: ['prompt injection', 'novel approval markers'],
};

const APPROVED: AllowlistConstraint = {
  type: 'constraint',
  enforcement: 'allowlist',
};

// LLM emitted id varies across cycles for the same operation
// Dedup on content hash instead:
const key = shellCommandHash(proposal.command); // sha256 of canonical form
if (seen.has(key)) skipApproval();

## Verification Gate

**Fixture:** <data set or scenario>
**Can the gate FAIL under this fixture?** <yes/no + algebraic rationale>
**Fixture-bindability proof:** <one sentence>
**Rehearsed at:** <commit-sha or "not yet">

# Commit plan (one per entity + scaffold + cleanup)
| # | Commit | Cumulative LOC |
|---|--------|----------------|
| 1 | scaffold | 1861 |
| 2 | extract people | 1694 |
| 8 | cleanup | 597 |

Is the action on the forbidden list (D)?  -> log + alert, STOP
Has an approved runbook (B)?              -> execute runbook, log, STOP
Reversible + low blast + pre-authorized?  -> Bucket A: execute, log
otherwise                                 -> Bucket C: propose, wait

# Hygiene procedure
1. Run the codemod on a clean tree.
2. Separate semantic hunks from reformatting hunks.
3. Revert incidental hunks (git checkout -p), re-apply only the semantic change.
4. OR run the formatter scoped to changed files BEFORE the codemod.