import { EngineStatus } from '../../engine/interfaces/whatsapp-engine.interface';
import type { IngressRouteDescriptor } from './ingress.service';

export type PreflightRejection = { status: number; body: string };

/**
 * Evaluates a route's host-side preflight checks. Returns null to PASS (proceed to dedup + ack + enqueue),
 * or a `{status, body}` to REJECT synchronously. Runs AFTER signature verify and BEFORE the dedup persist
 * (see IngressService.handle) — a rejection therefore writes no dedup row, so a provider retry on the 5xx
 * is treated as new (this is what avoids the dedup trap).
 *
 * `session-alive`: skipped for wildcard (null/'*') scopes and when sessionStatus is unwired; rejects 503
 * only when the concrete session has no live engine or is EngineStatus.FAILED. Recoverable statuses and
 * READY pass through to the normal 202+enqueue path so the worker can fail fast and the delivery stays durable.
 */
export function evaluatePreflight(
  route: IngressRouteDescriptor,
  sessionScope: string | null,
  sessionStatus: ((scope: string) => EngineStatus | undefined) | undefined,
): PreflightRejection | null {
  const checks = route.response?.preflight;
  if (!checks?.length) return null;
  for (const check of checks) {
    if (check.type === 'session-alive') {
      if (!sessionScope || sessionScope === '*') continue; // wildcard: no single session to probe
      if (!sessionStatus) continue; // unwired (pure unit mode): skip rather than false-reject
      const status = sessionStatus(sessionScope);
      if (status === undefined || status === EngineStatus.FAILED) {
        return { status: 503, body: 'session not ready' };
      }
    }
  }
  return null;
}