atomic-design-poc/libs/shared/src/infrastructure/api-error.ts

import { ProblemDetails } from './api-client';

/**
 * Extract a human-readable message from a rejected API call. A 4xx/5xx with a
 * ProblemDetails body (RFC 7807) is thrown by the generated client as the parsed
 * object; anything else falls back to the given message.
 */
export function problemDetail(e: unknown, fallback: string): string {
  if (e && typeof e === 'object' && 'detail' in e) {
    const detail = (e as ProblemDetails).detail;
    if (typeof detail === 'string' && detail) return detail;
  }
  return fallback;
}

/**
 * SEAM (G4): map a server validation envelope to field-level errors.
 *
 * ASP.NET's ValidationProblemDetails carries `errors: { field: string[] }`. The
 * backend today returns only `detail` (one banner message), so this returns `{}`.
 * When the backend starts sending `errors`, a machine's `SubmitFailed` handler can
 * merge this into its own `errors` map — the field-keyed shape the wizards already
 * render — so a rejection shows inline per field, not just as a banner. The
 * consumer hook is the only thing left to wire; the contract boundary lives here.
 */
export function problemFieldErrors(e: unknown): Record<string, string> {
  if (!e || typeof e !== 'object' || !('errors' in e)) return {};
  const errors = (e as { errors?: unknown }).errors;
  if (!errors || typeof errors !== 'object') return {};
  const out: Record<string, string> = {};
  for (const [field, msgs] of Object.entries(errors as Record<string, unknown>)) {
    const first = Array.isArray(msgs) ? msgs[0] : msgs;
    if (typeof first === 'string') out[field] = first;
  }
  return out;
}