export interface ParseBigIntOptions {
  /**
   * The number of digits starting from the right of the returned bigint to consider as decimal
   * places.
   *
   * @default 18n
   */
  precision?: bigint | undefined
  /**
   * If true, requires exact match (no commas, no extra whitespace)
   *
   * @default false
   */
  strict?: boolean | undefined
}

/**
 * Like `parseNumber()`, but returns a bigint instead of a number. Decimals to the right of
 * `precision` are truncated.
 *
 * @param value - The string to parse as a bigint.
 * @param options - Parsing options.
 * @returns The bigint representation of `value`, or `null` if we failed to parse it.
 */
export function parseBigInt(value: string, options?: ParseBigIntOptions) {
  const { precision = 18n, strict = false } = options ?? {}
  if (precision < 0n) {
    throw new Error(`[parseBigInt] \`precision\` must be positive, got ${precision}`)
  }

  const originalValue = value
  const cleanedValue = value.replace(/,/g, '').trim()

  if (strict && cleanedValue !== originalValue) return null
  if (cleanedValue === '' || cleanedValue === '-' || cleanedValue === '.' || cleanedValue === '-.')
    return null

  const [integerPart, decimalPart = '', somethingAfterDecimalPart] = cleanedValue.split('.')
  if (integerPart!.trim() !== integerPart) return null
  if (decimalPart.trim() !== decimalPart) return null
  if (somethingAfterDecimalPart !== undefined) return null

  try {
    const precisionNumber = Number(precision)
    return BigInt(
      `${integerPart}${decimalPart.slice(0, precisionNumber).padEnd(precisionNumber, '0')}`,
    )
  } catch {
    return null
  }
}