export type PaymentLineKind = 'BOOKING' | 'SUPPLEMENTARY';

export interface PaymentLine {
  kind: PaymentLineKind;
  /** Human label — "Original booking", "Reschedule", "Excess baggage". */
  label: string;
  /** Raw reason for supplementary lines (RESCHEDULE, UNDERPAYMENT, …); null for the booking line. */
  reason: string | null;
  /** Always true minor units, whatever the source column stored. */
  amountMinor: number;
  currency: string;
  status: string;
  paidAt: string | null;
  /** Whether this line represents money actually collected. */
  settled: boolean;
}

export interface PaymentBreakdown {
  lines: PaymentLine[];
  /** Sum of settled lines, or null when they are not all in one currency. */
  totalPaidMinor: number | null;
  totalPaidCurrency: string | null;
  /** True when something is still owed (a charge raised but not yet paid). */
  hasOutstanding: boolean;
  outstandingMinor: number;
}

/** `PaymentIntent.amountMinor` is a Float in major units — bring it onto the minor-unit scale. */
export function intentAmountToMinor(amount: number | null | undefined): number {
  if (amount == null) return 0;
  return Math.round(amount * 100);
}

const SUPPLEMENTARY_LABELS: Record<string, string> = {
  RESCHEDULE: 'Reschedule',
  UNDERPAYMENT: 'Underpayment',
  FARE_CORRECTION: 'Fare correction',
  EXCESS_BAGGAGE: 'Excess baggage',
};

function labelFor(reason: string): string {
  return (
    SUPPLEMENTARY_LABELS[reason] ??
    // "SOME_OTHER_REASON" → "Some other reason"
    reason.charAt(0).toUpperCase() + reason.slice(1).toLowerCase().replace(/_/g, ' ')
  );
}

export function buildPaymentBreakdown(
  paymentIntent: { status?: string | null; amountMinor?: number | null; currency?: string | null } | null | undefined,
  supplementaryCharges: Array<{
    reason: string;
    amountMinor: number;
    currency: string;
    status: string;
    paidAt: Date | string | null;
  }> = [],
): PaymentBreakdown {
  const lines: PaymentLine[] = [];

  if (paymentIntent) {
    lines.push({
      kind: 'BOOKING',
      label: 'Original booking',
      reason: null,
      amountMinor: intentAmountToMinor(paymentIntent.amountMinor),
      currency: paymentIntent.currency ?? 'ETB',
      status: paymentIntent.status ?? 'UNKNOWN',
      paidAt: null,
      settled: paymentIntent.status === 'SUCCEEDED',
    });
  }

  for (const charge of supplementaryCharges) {
    if (charge.status === 'WAIVED' || charge.status === 'EXPIRED') continue;
    lines.push({
      kind: 'SUPPLEMENTARY',
      label: labelFor(charge.reason),
      reason: charge.reason,
      amountMinor: charge.amountMinor,
      currency: charge.currency ?? 'ETB',
      status: charge.status,
      paidAt: charge.paidAt ? new Date(charge.paidAt).toISOString() : null,
      settled: charge.status === 'PAID',
    });
  }

  const settled = lines.filter((l) => l.settled);
  const currencies = new Set(settled.map((l) => l.currency));
  const singleCurrency = currencies.size === 1 ? [...currencies][0] : null;

  const outstanding = lines.filter((l) => l.status === 'PENDING');

  return {
    lines,
    totalPaidMinor: singleCurrency ? settled.reduce((sum, l) => sum + l.amountMinor, 0) : null,
    totalPaidCurrency: singleCurrency,
    hasOutstanding: outstanding.length > 0,
    outstandingMinor: outstanding.reduce((sum, l) => sum + l.amountMinor, 0),
  };
}