import { EventEmitter } from "../event-emitter.js";

/**
 * Events emitted by our Rates Adapters
 */
export type RatesEventMap = {
  rateUpdated: {
    numeratorUnitCode: string;
    denominatorUnitCode: string;
    price: number;
  };
};

export abstract class BaseRates<
  T extends RatesEventMap = RatesEventMap,
> extends EventEmitter<T> {
  /** Starts the given rates adapter so that it will emit events on price updates. */
  public abstract start(): Promise<void>;

  /** Stops the given rates adapter so that it will stop checking for price updates. */
  public abstract stop(): Promise<void>;

  /**
   * List all available market products (pairs).
   * @returns A set of strings in the format "NUMERATOR/DENOMINATOR"
   */
  public abstract listPairs(): Promise<Set<string>>;

  // TODO: Consider whether we actually want the below.
  //       Ideally, we will want to replace this with something like the Units class:
  //       See: https://gitlab.com/GeneralProtocols/xo/stack/-/issues/44
  /**
   * Format the amount in the target currency to the correct number of decimal places.
   *
   * @param {number} amount - The amount to format.
   * @param {string} targetCurrency - The target currency.
   *
   * @returns The formatted amount.
   */
  public formatCurrency(amount: number, targetCurrency: string): string {
    const normalizedCurrency = targetCurrency.toUpperCase();
    const minimumFractionDigitsMap: { [currency: string]: number } = {
      AUD: 2,
      BCH: 8,
      USD: 2,
    };
    const minimumFractionDigits =
      minimumFractionDigitsMap[normalizedCurrency] ?? 2;
    const maximumFractionDigits = Math.max(minimumFractionDigits, 8);

    try {
      const formatter = new Intl.NumberFormat("en-US", {
        style: "currency",
        currency: normalizedCurrency,
        currencyDisplay: "narrowSymbol",
        minimumFractionDigits,
        maximumFractionDigits,
      });

      return formatter.format(amount);
    } catch {
      // Some numerator symbols from oracle pairs (e.g. DOGE/BCH) are not ISO-4217
      // fiat currency codes, so Intl currency formatting will throw a RangeError.
      // In that case we still return a human-readable formatted value.
      const numericFormatter = new Intl.NumberFormat("en-US", {
        minimumFractionDigits,
        maximumFractionDigits,
      });
      return `${numericFormatter.format(amount)} ${normalizedCurrency}`;
    }
  }
}