/**
 * Money handling for PayMe.
 *
 * INTEGRATION RULE #1: PayMe amounts are ALWAYS integers in the currency's
 * minor unit — agorot for ILS, cents for USD/EUR. Never send a decimal amount
 * to the API. `sale_price: 5075` means 50.75.
 *
 * This is the most common source of a working-but-wrong integration. On
 * generate-sale PayMe does not reject a decimal `sale_price`: it rounds it to a
 * whole number before the range check. `50.75` becomes 51 and fails that check,
 * but `600.75` becomes 601 and charges 6.01. An amount sent in whole currency
 * units is also accepted when it is in range, and charges a hundredth of what
 * you meant: `600` charges 6.00, not 600.00. Keep money as integer minor units
 * everywhere in your own code and convert only at the display edge — that is
 * what this file exists to enforce.
 *
 * The default range for `sale_price` is 500 to 4000000 minor units, in every
 * currency; PayMe can set different limits per account. Outside it PayMe returns
 * error 352. Token sales are exempt, because PayMe sets their price itself.
 *
 * Reference: https://docs.payme.io/payments/hosted-payment-page/post-generate-sale
 */

/** PayMe's default minimum amount, in minor units (5.00). */
export const PAYME_MIN_AMOUNT_MINOR = 500;

/** Common currencies. PayMe accepts any 3-letter ISO 4217 code your account is enabled for. */
export const SUPPORTED_CURRENCIES = ['ILS', 'USD', 'EUR'] as const;
export type Currency = (typeof SUPPORTED_CURRENCIES)[number];

/**
 * Convert a human-entered decimal amount ("50.75") to PayMe minor units (5075).
 *
 * A minor-unit amount has at most two decimal places, so more are rejected
 * rather than rounded: float rounding of a third decimal is unreliable (1.005 *
 * 100 is 100.49999999999999). Within two decimals it rounds away float noise,
 * so 19.99 -> 1999, never 1998.
 */
export function toMinorUnits(amount: number | string): number {
  const text = typeof amount === 'string' ? amount.trim() : String(amount);
  // Plain non-negative decimals only. Number() alone would also accept
  // "1e3", "0x10" and "-5", and ports to other languages would differ.
  if (!/^\d+(\.\d+)?$/.test(text)) {
    throw new Error(`Cannot convert "${amount}" to minor units`);
  }
  if (/\.\d{3,}$/.test(text)) {
    throw new Error(`"${amount}" has more than two decimal places`);
  }
  const minor = Math.round(Number(text) * 100);
  if (!Number.isSafeInteger(minor)) {
    throw new Error(`"${amount}" is too large to represent exactly`);
  }
  return minor;
}

/** Convert PayMe minor units (5075) back to a decimal number (50.75) for display. */
export function fromMinorUnits(minor: number): number {
  return minor / 100;
}

/** Format minor units for humans: 5075, 'ILS' -> "₪50.75". */
export function formatMinorUnits(minor: number, currency: string): string {
  return new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency,
  }).format(fromMinorUnits(minor));
}