/**
 * @rajeev02/payments — Cards & Subscriptions
 * Card tokenization (RBI compliant), saved cards, recurring billing
 */

export interface CardInfo {
  /** Tokenized card reference (never store raw card numbers) */
  tokenRef: string;
  /** Last 4 digits for display */
  last4: string;
  /** Card network */
  network: "visa" | "mastercard" | "rupay" | "amex" | "dinersclub";
  /** Card type */
  type: "credit" | "debit" | "prepaid";
  /** Issuing bank name */
  issuerBank?: string;
  /** Expiry month */
  expiryMonth: number;
  /** Expiry year */
  expiryYear: number;
  /** Cardholder name */
  holderName?: string;
  /** Whether card supports recurring/mandate */
  supportsRecurring: boolean;
}

export interface SubscriptionPlan {
  id: string;
  name: string;
  description?: string;
  amount: number;
  currency: string;
  interval: "daily" | "weekly" | "monthly" | "quarterly" | "yearly";
  intervalCount: number;
  trialDays?: number;
  features?: string[];
}

export interface Subscription {
  id: string;
  planId: string;
  customerId: string;
  status:
    | "active"
    | "paused"
    | "cancelled"
    | "past_due"
    | "trialing"
    | "expired";
  currentPeriodStart: string;
  currentPeriodEnd: string;
  cancelledAt?: string;
  paymentMethod: "card" | "upi_mandate" | "emandate";
  tokenRef?: string;
  nextBillingDate: string;
  amount: number;
}

/**
 * Detect card network from number prefix (first 6 digits)
 */
export function detectCardNetwork(
  cardNumber: string,
): CardInfo["network"] | null {
  const digits = cardNumber.replace(/\s/g, "");
  if (digits.startsWith("4")) return "visa";
  if (/^5[1-5]/.test(digits) || /^2[2-7]/.test(digits)) return "mastercard";
  if (/^6(0|5|52[12]|53[89]|5[4-9]|[6-9])/.test(digits)) return "rupay";
  if (/^3[47]/.test(digits)) return "amex";
  if (/^3(0[0-5]|[68])/.test(digits)) return "dinersclub";
  return null;
}

/**
 * Format card number with spaces: 4111111111111111 → 4111 1111 1111 1111
 */
export function formatCardNumber(cardNumber: string): string {
  const digits = cardNumber.replace(/\D/g, "");
  if (detectCardNetwork(digits) === "amex") {
    return digits.replace(/(\d{4})(\d{6})(\d{5})/, "$1 $2 $3");
  }
  return digits.replace(/(\d{4})/g, "$1 ").trim();
}

/**
 * Validate card number using Luhn algorithm
 */
export function validateCardNumber(cardNumber: string): boolean {
  const digits = cardNumber.replace(/\D/g, "");
  if (digits.length < 13 || digits.length > 19) return false;

  let sum = 0;
  let isEven = false;
  for (let i = digits.length - 1; i >= 0; i--) {
    let d = parseInt(digits[i], 10);
    if (isEven) {
      d *= 2;
      if (d > 9) d -= 9;
    }
    sum += d;
    isEven = !isEven;
  }
  return sum % 10 === 0;
}

/**
 * Calculate subscription renewal dates
 */
export function getNextBillingDate(
  plan: SubscriptionPlan,
  currentDate: Date = new Date(),
): Date {
  const next = new Date(currentDate);
  switch (plan.interval) {
    case "daily":
      next.setDate(next.getDate() + plan.intervalCount);
      break;
    case "weekly":
      next.setDate(next.getDate() + 7 * plan.intervalCount);
      break;
    case "monthly":
      next.setMonth(next.getMonth() + plan.intervalCount);
      break;
    case "quarterly":
      next.setMonth(next.getMonth() + 3 * plan.intervalCount);
      break;
    case "yearly":
      next.setFullYear(next.getFullYear() + plan.intervalCount);
      break;
  }
  return next;
}