export function inet_pton(a: string): string | false {
  //      discuss at: https://locutus.io/php/inet_pton/
  // parity verified: PHP 8.3
  //     original by: Theriault (https://github.com/Theriault)
  //     improved by: alromh87 and JamieSlome
  //       example 1: inet_pton('::')
  //       returns 1: '\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0'
  //       example 2: inet_pton('127.0.0.1')
  //       returns 2: '\x7F\x00\x00\x01'

  const f = String.fromCharCode

  // IPv4
  const ipv4Match = a.match(/^(?:\d{1,3}(?:\.|$)){4}/)
  if (ipv4Match) {
    const octets = ipv4Match[0]
      .split('.')
      .slice(0, 4)
      .map((part) => Number.parseInt(part, 10))
    const [a0, a1, a2, a3] = octets
    if (
      a0 === undefined ||
      a1 === undefined ||
      a2 === undefined ||
      a3 === undefined ||
      octets.some((octet) => Number.isNaN(octet) || octet < 0 || octet > 255)
    ) {
      return false
    }
    const packed = f(a0, a1, a2, a3)
    // Return if 4 bytes, otherwise false.
    return packed.length === 4 ? packed : false
  }

  // IPv6
  if (a.length > 39) {
    return false
  }

  const segments = a.split('::')

  if (segments.length > 2) {
    return false
  } // :: can't be used more than once in IPv6.

  const reHexDigits = /^[\da-f]{1,4}$/i

  const packedSegments: string[] = []
  for (const segment of segments) {
    if (segment.length === 0) {
      packedSegments.push('')
      continue
    }
    const hextets = segment.split(':')
    let packed = ''
    for (const hextetSource of hextets) {
      const hextet = hextetSource
      // check if valid hex string up to 4 chars
      if (!reHexDigits.test(hextet)) {
        return false
      }

      const parsedHextet = parseInt(hextet, 16)

      // Would be NaN if it was blank, return false.
      if (Number.isNaN(parsedHextet)) {
        // Invalid IP.
        return false
      }
      packed += f(parsedHextet >> 8, parsedHextet & 0xff)
    }
    packedSegments.push(packed)
  }

  const bytesLength = packedSegments.reduce((total, part) => total + part.length, 0)
  if (bytesLength > 16) {
    return false
  }

  if (segments.length === 1 && bytesLength !== 16) {
    return false
  }

  return packedSegments.join('\x00'.repeat(16 - bytesLength))
}