import { sql } from 'kysely';
import { pendingMigrations } from '../db/migrator';
import type { AppDeps } from './context';

export type CheckState = 'ok' | 'error' | 'pending';

/**
 * Liveness: the process is up and the event loop is turning. Never touches the
 * database, so a database blip does not get the container killed.
 */
export function liveness(draining: boolean): { ok: boolean } {
  return { ok: !draining };
}

/**
 * Readiness: this replica can serve traffic. Checked by the orchestrator and flipped
 * to not-ready as soon as SIGTERM arrives, so the load balancer stops sending work
 * while in flight requests drain.
 */
export async function readiness(
  deps: AppDeps,
  draining: boolean,
): Promise<{ ok: boolean; checks: Record<string, CheckState> }> {
  if (draining) return { ok: false, checks: { draining: 'error' } };

  const checks: Record<string, CheckState> = {};

  try {
    await sql`select 1`.execute(deps.handle.db);
    checks['database'] = 'ok';
  } catch {
    checks['database'] = 'error';
  }

  if (checks['database'] === 'ok') {
    try {
      checks['migrations'] = (await pendingMigrations(deps.handle)).length === 0 ? 'ok' : 'pending';
    } catch {
      checks['migrations'] = 'error';
    }
  } else {
    checks['migrations'] = 'error';
  }

  try {
    await deps.storage.check();
    checks['storage'] = 'ok';
  } catch {
    checks['storage'] = 'error';
  }

  return { ok: Object.values(checks).every((state) => state === 'ok'), checks };
}