export type NormalizePriceInput = {
  amount: number;
  currency: string;
  exchangeRates?: Record<string, number>;
};

export type NormalizedPrice = {
  currency: "USD";
  amountUsd: number;
  notes: string[];
};

export function normalizePriceToUsd(
  input: NormalizePriceInput
): NormalizedPrice {
  const currency = input.currency.trim().toUpperCase();
  if (currency === "USD") {
    return {
      currency: "USD",
      amountUsd: input.amount,
      notes: ["Price already in USD."]
    };
  }

  const rate = input.exchangeRates?.[currency];
  if (typeof rate !== "number" || !Number.isFinite(rate) || rate <= 0) {
    throw new Error(`Missing usable exchange rate for ${currency}.`);
  }

  const amountUsd = Math.round(input.amount * rate * 100) / 100;
  return {
    currency: "USD",
    amountUsd,
    notes: [`Converted ${currency} to USD using rate ${rate}.`]
  };
}