/**
 * Money is always integer minor units (cents). Never floats — 0.1 + 0.2 problems
 * become customer support tickets when they happen to someone's payout.
 */

export type Cents = number;

export class MoneyError extends Error {}

export function assertCents(value: number, label = 'amount'): asserts value is Cents {
  if (!Number.isInteger(value)) throw new MoneyError(`${label} must be an integer, got ${value}`);
  if (value < 0) throw new MoneyError(`${label} must not be negative, got ${value}`);
  if (!Number.isSafeInteger(value)) throw new MoneyError(`${label} exceeds safe integer range`);
}

/** Basis points: 1500 bps = 15%. */
export type Bps = number;

/**
 * Platform commission. Rounds half-up so the platform never takes a fraction of a
 * cent more than stated, and the pro's share absorbs the remainder.
 */
export function platformFee(amount: Cents, feeBps: Bps): Cents {
  assertCents(amount);
  if (!Number.isInteger(feeBps) || feeBps < 0 || feeBps > 10_000) {
    throw new MoneyError(`feeBps must be an integer in [0, 10000], got ${feeBps}`);
  }
  return Math.round((amount * feeBps) / 10_000);
}

/** What actually lands in the pro's connected account. */
export function proPayout(amount: Cents, feeBps: Bps): Cents {
  return amount - platformFee(amount, feeBps);
}

/** Split a charge into its parts. The two always sum back to `amount`. */
export function splitCharge(amount: Cents, feeBps: Bps): { fee: Cents; payout: Cents } {
  const fee = platformFee(amount, feeBps);
  return { fee, payout: amount - fee };
}

export function formatCents(amount: Cents, currency = 'EUR', locale = 'en-IE'): string {
  return new Intl.NumberFormat(locale, { style: 'currency', currency }).format(amount / 100);
}

export function parseAmountToCents(input: string): Cents {
  const normalised = input.replace(/[^0-9.,-]/g, '').replace(',', '.');
  const parsed = Number.parseFloat(normalised);
  if (Number.isNaN(parsed)) throw new MoneyError(`Cannot parse "${input}" as an amount`);
  return Math.round(parsed * 100);
}