// Return policy rules stored in database and evaluated programmatically
interface ReturnPolicy {
  id: string;
  name: string;
  priority: number;           // higher = evaluated first
  conditions: {
    productTags?: string[];   // match any of these tags
    customerTags?: string[];  // match any of these customer tags
    orderTags?: string[];     // e.g., ['final-sale']
  };
  windowDays: number;         // 0 = no returns allowed
  restockingFeePct: number;   // 0–100
  autoApprove: boolean;
}

async function evaluateReturnEligibility(params: {
  orderId: string;
  productId: string;
  customerId: string;
  returnReason: string;
  deliveredAt: Date;
}): Promise<{
  eligible: boolean;
  policy: ReturnPolicy | null;
  restockingFeeCents: number;
  requiresManualReview: boolean;
  daysRemaining: number;
  reason?: string;
}> {
  const order = await db.orders.findById(params.orderId);
  const product = await db.products.findById(params.productId, { include: ['tags'] });
  const customer = await db.customers.findById(params.customerId, { include: ['tags'] });

  // Find highest-priority matching policy
  const policies = await db.returnPolicies.findAll({ is_active: true }, { orderBy: ['priority', 'desc'] });
  const policy = policies.find(p => {
    const productMatch = !p.conditions.productTags?.length ||
      p.conditions.productTags.some(tag => product.tags.includes(tag));
    const customerMatch = !p.conditions.customerTags?.length ||
      p.conditions.customerTags.some(tag => customer.tags.includes(tag));
    const orderMatch = !p.conditions.orderTags?.length ||
      p.conditions.orderTags.some(tag => order.tags?.includes(tag));
    return productMatch && customerMatch && orderMatch;
  }) ?? null;

  if (!policy || policy.windowDays === 0) {
    return { eligible: false, policy, restockingFeeCents: 0, requiresManualReview: false, daysRemaining: 0, reason: 'FINAL_SALE_OR_NO_POLICY' };
  }

  // Calculate days since delivery
  const daysSinceDelivery = Math.floor((Date.now() - params.deliveredAt.getTime()) / 86400000);
  const daysRemaining = policy.windowDays - daysSinceDelivery;

  if (daysRemaining < 0) {
    return { eligible: false, policy, restockingFeeCents: 0, requiresManualReview: false, daysRemaining: 0, reason: 'WINDOW_EXPIRED' };
  }

  // Calculate restocking fee on the item's original price
  const orderLine = await db.orderLines.findOne({ order_id: params.orderId, product_id: params.productId });
  const itemValueCents = orderLine.unit_price_cents * orderLine.quantity;
  const restockingFeeCents = Math.round(itemValueCents * (policy.restockingFeePct / 100));

  return {
    eligible: true,
    policy,
    restockingFeeCents,
    requiresManualReview: !policy.autoApprove,
    daysRemaining,
  };
}