Assist_Design/packages/domain/src/entities/billing.ts

/**
 * Billing Domain Entities
 * 
 * Business entities for billing calculations and summaries
 */

export interface BillingSummaryData {
  totalOutstanding: number;
  totalOverdue: number;
  totalPaid: number;
  currency: string;
  currencySymbol?: string;
  invoiceCount: {
    total: number;
    unpaid: number;
    overdue: number;
    paid: number;
  };
}

// Money representation (business concept)
export interface Money {
  amount: number;
  currency: string;
}

// Currency formatting options (business rules)
export interface CurrencyFormatOptions {
  currency?: string;
  locale?: string;
  minimumFractionDigits?: number;
  maximumFractionDigits?: number;
}

// Business logic for billing calculations
export function calculateBillingSummary(invoices: Array<{
  total: number;
  status: string;
  dueDate?: string;
  paidDate?: string;
}>): Omit<BillingSummaryData, 'currency' | 'currencySymbol'> {
  const now = new Date();
  
  return invoices.reduce((summary, invoice) => {
    const isOverdue = invoice.dueDate && new Date(invoice.dueDate) < now && !invoice.paidDate;
    const isPaid = !!invoice.paidDate;
    const isUnpaid = !isPaid;

    return {
      totalOutstanding: summary.totalOutstanding + (isUnpaid ? invoice.total : 0),
      totalOverdue: summary.totalOverdue + (isOverdue ? invoice.total : 0),
      totalPaid: summary.totalPaid + (isPaid ? invoice.total : 0),
      invoiceCount: {
        total: summary.invoiceCount.total + 1,
        unpaid: summary.invoiceCount.unpaid + (isUnpaid ? 1 : 0),
        overdue: summary.invoiceCount.overdue + (isOverdue ? 1 : 0),
        paid: summary.invoiceCount.paid + (isPaid ? 1 : 0),
      },
    };
  }, {
    totalOutstanding: 0,
    totalOverdue: 0,
    totalPaid: 0,
    invoiceCount: {
      total: 0,
      unpaid: 0,
      overdue: 0,
      paid: 0,
    },
  });
}