import type { StoreCapabilities } from 'brainerce';

/**
 * Fallback used until `getStoreCapabilities()` resolves, and whenever the call
 * fails. Matches the platform default (`SalesChannel.lowStockThreshold`), so a
 * store that never reaches the endpoint behaves exactly as it did before
 * capabilities were wired in — it never renders a broken or empty badge.
 */
export const DEFAULT_LOW_STOCK_THRESHOLD = 5;

/**
 * The subset of {@link StoreCapabilities} the storefront actually renders from.
 * Operational channel state (granted API scopes, sandbox payment flags,
 * reservation strategy) is deliberately dropped: it tells a reader how the
 * merchant's channel is provisioned and has no role in what a shopper sees.
 *
 * Uses indexed access on `StoreCapabilities` for nested types so this stays in
 * step with the SDK without restating its shapes.
 */
export interface PublicStoreCapabilities {
  /** Whether to call out low stock at all. False means the merchant switched the urgency messaging off. */
  lowStockWarning: boolean;
  /** Units at or below which stock counts as low. */
  lowStockThreshold: number;
  /** Whether "email me when this is back" should be offered on sold-out items. */
  stockAlertsEnabled: boolean;
  /** Minutes a checkout reservation is held before it expires. */
  reservationTimeout: number;
  /** Which optional features the merchant enabled — coupons, loyalty, shipping zones, and so on. */
  features: StoreCapabilities['features'];
}

/**
 * Project a raw capabilities response onto {@link PublicStoreCapabilities}.
 * Add a field here only after confirming it is non-sensitive and that a
 * storefront component actually needs it.
 */
export function pickPublicCapabilities(raw: StoreCapabilities): PublicStoreCapabilities {
  return {
    lowStockWarning: raw.connection.lowStockWarning,
    lowStockThreshold: raw.connection.lowStockThreshold,
    stockAlertsEnabled: raw.connection.stockAlertsEnabled,
    reservationTimeout: raw.connection.reservationTimeout,
    features: raw.features,
  };
}

/**
 * Resolve the low-stock threshold a badge should use.
 *
 * Three cases, in order:
 *  1. Capabilities not loaded yet, or the fetch failed (`null`) — fall back to
 *     {@link DEFAULT_LOW_STOCK_THRESHOLD} so the first paint is correct.
 *  2. The merchant turned the low-stock warning off — return `0`. Stock counts
 *     as low only at or below the threshold, and an in-stock item always has at
 *     least one unit, so nothing is ever flagged low. The item still renders its
 *     normal in-stock label; no string is left blank.
 *  3. Otherwise, the merchant's configured threshold.
 */
export function resolveLowStockThreshold(
  capabilities: PublicStoreCapabilities | null | undefined
): number {
  if (!capabilities) return DEFAULT_LOW_STOCK_THRESHOLD;
  return capabilities.lowStockWarning ? capabilities.lowStockThreshold : 0;
}