const WEI_DECIMALS = 18n

export function formatWeiAsEth(value: string, fractionDigits = 4): string {
  try {
    const normalizedDigits = Math.max(0, Math.min(18, fractionDigits))
    const wei = BigInt(value)
    const divisor = 10n ** WEI_DECIMALS
    const whole = wei / divisor
    const fraction = wei % divisor

    if (normalizedDigits === 0) {
      return `${whole.toString()} ETH`
    }

    const scale = 10n ** (WEI_DECIMALS - BigInt(normalizedDigits))
    const truncatedFraction = fraction / scale
    const paddedFraction = truncatedFraction
      .toString()
      .padStart(normalizedDigits, '0')
      .replace(/0+$/, '')

    if (!paddedFraction) {
      return `${whole.toString()} ETH`
    }

    return `${whole.toString()}.${paddedFraction} ETH`
  } catch {
    return '0 ETH'
  }
}