const API_BASE = process.env.NEXT_PUBLIC_CORE_API_BASE ?? "";

export class ApiError extends Error {}

async function req<T>(path: string, init?: RequestInit): Promise<T> {
  const res = await fetch(`${API_BASE}${path}`, {
    credentials: "include",
    headers: init?.body ? { "Content-Type": "application/json" } : undefined,
    ...init,
  });
  const data = await res.json().catch(() => ({}));
  if (!res.ok) {
    throw new ApiError(data.error ?? data.message ?? "Unbekannter Fehler");
  }
  return data as T;
}

export interface Preference {
  TenantSlug: string;
  UserID: string;
  EventType: string;
  Channel: string;
  Enabled: boolean;
}

// Bekannte Ereignistypen/Kanäle — das Backend erzwingt keine feste Liste
// (jedes Modul kann eigene event_type-Werte an EnqueueIfAllowed übergeben),
// diese Liste ist der aktuell bekannte Stand fürs Frontend-Formular.
export const KNOWN_EVENT_TYPES = ["welcome", "invoice_ready", "password_reset", "security_alert"] as const;
export const KNOWN_CHANNELS = ["email", "in_app"] as const;

export function fetchMyPreferences(): Promise<Preference[]> {
  return req("/notifications/preferences");
}

export function setPreference(eventType: string, channel: string, enabled: boolean): Promise<void> {
  return req("/notifications/preferences", {
    method: "POST",
    body: JSON.stringify({ event_type: eventType, channel, enabled }),
  });
}

export function fetchTenantOverview(): Promise<Preference[]> {
  return req("/notifications/preferences/tenant");
}