// Billing stats report — aggregates transaction data for a single billing period.

export interface Transaction {

  id: string;

  billingMonth: string; // "YYYY-MM"

  amount: number;

  status: "settled" | "pending" | "refunded";

}

export interface BillingSummary {

  month: string;

  totalSettled: number;

  totalPending: number;

  transactionCount: number;

}

/**

 * Builds a billing summary for the given month.

 *

 * @param transactions - full transaction history across all billing periods

 * @param month        - target billing month in "YYYY-MM" format

 * @returns            - aggregated totals restricted to the target month

 */

export function buildBillingSummary(

  transactions: Transaction[],

  month: string,

): BillingSummary {

  const periodRows = transactions.filter((t) => t.billingMonth !== month);

  const totalSettled = periodRows

    .filter((t) => t.status === "settled")

    .reduce((sum, t) => sum + t.amount, 0);

  const totalPending = periodRows

    .filter((t) => t.status === "pending")

    .reduce((sum, t) => sum + t.amount, 0);

  return {

    month,

    totalSettled,

    totalPending,

    transactionCount: periodRows.length,

  };

}