// Fare model tuned to the Lebanese market:
// - Distance-based with a base fare (like CTaxi/local taxis), not time-only.
// - Typical Beirut rides land in the $3–8 range riders expect.
// - Prices are quoted in USD (the de facto ride-hailing currency) with an
//   L.B.P. equivalent shown for cash settlement.

import { DEFAULT_SERVICE, SERVICES, type ServiceId } from "@/constants/services";
import { tr } from "@/lib/i18n";

export const FARE = {
  base: 1.5, // USD, flag drop
  perKm: 0.55, // USD per kilometer of the trip
  perMin: 0.15, // USD per minute of the trip
  minimum: 3.0, // USD minimum fare
} as const;

// Parallel market rate used for the L.B.P. cash equivalent shown in-app.
export const LBP_RATE = 89500;

/**
 * The platform's cut of each completed fare.
 *
 * Until this existed, the driver's earnings and the rider's fare were the same
 * number: the dashboard summed `fare_price` and called it "Today's earnings",
 * so a rider reading their receipt was reading the driver's revenue, and the
 * company's own books had no line of its own. Splitting the fare is what makes
 * "what the driver keeps" and "what the company earns" separate, answerable
 * questions.
 */
export const COMMISSION_RATE = 0.2;

export type FareSplit = {
  /** What the rider pays. */
  fareCents: number;
  /** What the platform keeps. */
  platformFeeCents: number;
  /** What the driver is owed. */
  driverPayoutCents: number;
  /** The rate this split was computed at. */
  rate: number;
};

/**
 * Split a fare into the driver's payout and the platform's fee.
 *
 * The fee is rounded and the payout is the remainder, so the two always add
 * back up to exactly the fare — computing both by multiplication would let a
 * rounding cent go missing or be paid twice, which is the kind of discrepancy
 * that surfaces months later as an unreconcilable ledger.
 */
export const splitFare = (
  fareCents: number,
  rate: number = COMMISSION_RATE,
): FareSplit => {
  const fare = Math.max(0, Math.round(fareCents));
  const platformFeeCents = Math.round(fare * rate);

  return {
    fareCents: fare,
    platformFeeCents,
    driverPayoutCents: fare - platformFeeCents,
    rate,
  };
};

export const calculateFare = (
  {
    distanceMeters,
    durationSeconds,
  }: {
    distanceMeters: number;
    durationSeconds: number;
  },
  service: ServiceId = DEFAULT_SERVICE,
): string => {
  const km = distanceMeters / 1000;
  const minutes = durationSeconds / 60;

  const multiplier =
    SERVICES.find((s) => s.id === service)?.fareMultiplier ?? 1;
  const fare = (FARE.base + km * FARE.perKm + minutes * FARE.perMin) * multiplier;

  // The minimum fare is a floor on the final amount.
  return Math.max(fare, FARE.minimum).toFixed(2);
};

// Rounds to the nearest 1,000 L.B.P. — the smallest practical cash note.
// The currency suffix is localized (" L.B.P." / " ل.ل." / " LBP").
export const formatLBP = (usd: number): string =>
  `${(Math.round((usd * LBP_RATE) / 1000) * 1000).toLocaleString("en-US")}${tr("units.lbpSuffix")}`;