import { callbackKind, str } from './callback-fields';

/**
 * Framework-free callback routing for a DIRECT SELLER. Your route handler:
 *
 *   1. parse the body (PayMe POSTs application/x-www-form-urlencoded)
 *   2. const decision = decideSellerCallback(body)
 *   3. record the event; for 'verify-by-query', look the record up by the id
 *      YOU stored, query PayMe and apply only what it confirms:
 *      sale -> get-transactions -> verifySaleAgainstTransactions()
 *      subscription -> get-subscriptions -> verifySubscriptionAgainstQuery()
 *   4. answer HTTP 200 for every decision you recorded
 *
 * A direct seller cannot check `payme_signature` (it is computed with partner
 * credentials), and subscription callbacks carry none at all, so no callback
 * body is ever trusted on its own.
 *
 * Reference: https://docs.payme.io/payments/getting-started/callbacks
 */

export type SellerCallbackKind = 'sale' | 'subscription' | 'partner' | 'unknown';

export type SellerCallbackDecision =
  /** Confirm with get-transactions, then apply PayMe's answer — never the body. */
  | { action: 'verify-by-query'; kind: 'sale'; paymeSaleId: string; reason: string }
  /** Confirm with get-subscriptions, then apply PayMe's answer — never the body. */
  | { action: 'verify-by-query'; kind: 'subscription'; subPaymeId: string; reason: string }
  /** Record it; change nothing because of it. */
  | { action: 'record'; kind: SellerCallbackKind; reason: string };

export function decideSellerCallback(
  body: Record<string, unknown>,
): SellerCallbackDecision {
  const kind = callbackKind(body);

  switch (kind) {
    case 'sale': {
      const paymeSaleId = str(body.payme_sale_id);
      return paymeSaleId
        ? {
            action: 'verify-by-query',
            kind,
            paymeSaleId,
            reason: 'Sale callback: confirm with get-transactions before acting.',
          }
        : {
            action: 'record',
            kind,
            reason: 'Sale callback without payme_sale_id: nothing to look up.',
          };
    }

    case 'subscription': {
      const subPaymeId = str(body.sub_payme_id);
      return subPaymeId
        ? {
            action: 'verify-by-query',
            kind,
            subPaymeId,
            reason: 'Subscription callback: confirm with get-subscriptions before acting.',
          }
        : {
            action: 'record',
            kind,
            reason: 'Subscription callback without sub_payme_id: nothing to look up.',
          };
    }

    case 'seller':
    case 'withdrawal':
      // PayMe sends these to the partner's callback URL, not to a seller's.
      return {
        action: 'record',
        kind: 'partner',
        reason: 'Seller and payout notifications are sent to partners; not expected here.',
      };

    default:
      return {
        action: 'record',
        kind,
        reason: `Unknown notify_type ${JSON.stringify(body.notify_type ?? null)}.`,
      };
  }
}