import Decimal from 'decimal.js'

const CURRENCY_SYMBOL: Record<string, string> = {
  RUB: '₽',
  USD: '$',
  EUR: '€',
}

const DEFAULT_FORMAT: string = '{amount} {currency}'
const CURRENCY_FORMAT: Record<string, string> = {
  USD: '{currency}{amount}',
  RUB: '{amount}{currency}',
  EUR: '{currency}{amount}',
}

const DEFAULT_EXPONENT: number = 2
const CURRENCY_EXPONENT: Record<string, number> = {
  BTC: 6,
  USDT: 2,
}

function getSymbol(currency: string): string {
  return CURRENCY_SYMBOL[currency] ?? currency
}

function getFormat(currency: string): string {
  return CURRENCY_FORMAT[currency] ?? DEFAULT_FORMAT
}

function getExponent(currency: string): number {
  return CURRENCY_EXPONENT[currency] ?? DEFAULT_EXPONENT
}

function format(value: Decimal.Value, currency: string): string {
  const exponent = getExponent(currency)

  try {
    return new Decimal(value).toFixed(exponent)
  }
  catch {
    return new Decimal(0).toFixed(exponent)
  }
}

function fullFormat(value: Decimal.Value, currency: string, showCurrency = true, approximately = false): string {
  let result = ''
  let decimalValue: Decimal.Instance
  const exponent = getExponent(currency)

  try {
    decimalValue = new Decimal(value)
  }
  catch {
    decimalValue = new Decimal(0)
  }

  value = decimalValue.toFixed(exponent)

  if (approximately && !decimalValue.isZero())
    result = '~'

  if (showCurrency) {
    const symbol = getSymbol(currency)
    const format = getFormat(currency)

    result += format.replace('{amount}', value).replace('{currency}', symbol)
  }
  else {
    result += value
  }

  return result
}

function convert(amount: Decimal.Value, rate: Decimal.Value, isTurnRate = true) {
  if (isTurnRate)
    return Decimal.mul(amount, rate)
  else
    return Decimal.div(amount, rate)
}

export const $money = {
  getSymbol,
  getFormat,
  getExponent,
  format,
  fullFormat,
  convert,
}