import BN from 'bn.js';

import { Opaque, Option } from '../utils/types';
import { assert } from '../utils/assert';

export type BigNumber = Opaque<BN, 'BigNumber'>;
export type BigNumberValues =
  | number
  | string
  | number[]
  | Uint8Array
  | Buffer
  | BN;

export const toBigNumber = (
  value: BigNumberValues,
  endian?: BN.Endianness
): BigNumber => {
  return new BN(value, endian) as BigNumber;
};

export const toOptionBigNumber = (
  value: Option<BigNumberValues>
): Option<BigNumber> => {
  return value === null ? null : toBigNumber(value);
};

export const isBigNumber = (value: any): value is BigNumber => {
  return value?.__opaque__ === 'BigNumber';
};

export function assertBigNumber(value: any): asserts value is BigNumber {
  assert(isBigNumber(value), 'Expected BigNumber type');
}

export type Fraction = {
  mantissa: BN;
  decimals: number;
};

export const toFractional = (mantissa: BN | number, decimals = 0): Fraction => {
  if (typeof mantissa === 'number') {
    mantissa = new BN(mantissa);
  }

  return { mantissa: mantissa as BN, decimals };
};