RosettaCodeData/Task/Parse-an-IP-Address/FreeBASIC/parse-an-ip-address.basic

Function isNumericString(s As String) As Boolean
    For i As Integer = 1 To Len(s)
        Dim c As String = Mid(s, i, 1)
        If c < "0" Or c > "9" Then Return False
    Next
    Return True
End Function

Function isHexString(s As String) As Boolean
    For i As Integer = 1 To Len(s)
        Dim c As String = Mid(s, i, 1)
        If Not ((c >= "0" And c <= "9") Or (c >= "a" And c <= "f") Or (c >= "A" And c <= "F")) Then Return False
    Next
    Return True
End Function

Function Split(text As String, delimiter As String, arr() As String) As Integer
    If Len(text) = 0 Then Return 0

    Dim As Integer cnt = 0, posic = 0, lastPos = 0
    Redim arr(8)  ' Pre-allocate array with sufficient size

    Do
        posic = Instr(lastPos + 1, text, delimiter)
        If posic = 0 Then
            If lastPos < Len(text) Then
                arr(cnt) = Mid(text, lastPos + 1)
                cnt += 1
            End If
            Exit Do
        End If

        arr(cnt) = Mid(text, lastPos + 1, posic - lastPos - 1)
        cnt += 1
        lastPos = posic
    Loop

    Return cnt
End Function

Function parseIP(addr As String) As String
    Dim As String result = "IP address   : " & addr & !"\n"
    Dim As String parts(8), ipParts(8)
    Dim As Integer cnt, i
    Dim As String port = "not specified"

    ' Check if it's an IPv4 address
    cnt = Split(addr, ":", parts())

    ' IPv4 processing
    cnt = Split(parts(0), ".", ipParts())
    If cnt = 4 Then
        Dim As String hexa = ""
        Dim As Boolean valid = True

        For i = 0 To 3
            Dim As Integer value = Valint(ipParts(i))
            If value >= 0 Andalso value <= 255 Then
                hexa &= Right("0" & Hex(value), 2)
            Else
                valid = False
                Exit For
            End If
        Next

        If valid Then
            result &= "Address      : " & hexa & !"\n"
            result &= "Address Space: IPv4" & !"\n"
            If Len(parts(1)) > 0 Then
                Dim As Integer portVal = Valint(parts(1))
                If portVal >= 0 Andalso portVal <= 65535 Then
                    result &= "Port         : " & parts(1) & !"\n"
                End If
            Else
                result &= "Port         : not specified" & !"\n"
            End If
            Return result
        End If
    End If

    ' Check if it's an IPv6 address
    If Instr(addr, ":") > 0 Then
        Dim As String ipv6Addr = addr

        If Left(addr, 1) = "[" Then
            Dim As Integer endBracket = Instr(addr, "]")
            If endBracket > 0 Then
                ipv6Addr = Mid(addr, 2, endBracket - 2)
                If endBracket < Len(addr) Then
                    port = Mid(addr, endBracket + 2)
                End If
            End If
        End If

        ' Special handling for IPv4-mapped IPv6 addresses
        If Instr(ipv6Addr, "::ffff:") > 0 Then
            Dim As String ipv4Part = Mid(ipv6Addr, Instr(ipv6Addr, "::ffff:") + 7)
            cnt = Split(ipv4Part, ".", ipParts())

            If cnt = 4 Then
                Dim As String hexa = "FFFF"
                Dim As Boolean valid = True

                For i = 0 To 3
                    Dim As Integer value = Valint(ipParts(i))
                    If value >= 0 Andalso value <= 255 Then
                        hexa &= Right("0" & Hex(value), 2)
                    Else
                        valid = False
                        Exit For
                    End If
                Next

                If valid Then
                    result &= "Address      : " & hexa & !"\n"
                    result &= "Address Space: IPv6" & !"\n"
                    result &= "Port         : " & port & !"\n"
                    Return result
                End If
            End If
            ' If IPv4 part is invalid, return invalid address
            Return result & "Address      : Invalid Address" & !"\n"
        End If

        cnt = Split(ipv6Addr, ":", ipParts())
        If cnt > 0 Then
            Dim As String hexa = ""
            Dim As Integer emptyIndex = -1

            ' Find :: position
            For i = 0 To cnt - 1
                If Len(ipParts(i)) = 0 Then
                    emptyIndex = i
                    Exit For
                End If
            Next

            ' Process parts before ::
            For i = 0 To emptyIndex - 1
                hexa &= Right("0000" & ipParts(i), 4)
            Next

            ' Fill middle with zeros
            If emptyIndex >= 0 Then
                Dim As Integer zerosNeeded = 8 - (cnt - 1)
                hexa &= String(zerosNeeded * 4, "0")
            End If

            ' Process parts after ::
            For i = emptyIndex + 1 To cnt - 1
                hexa &= Right("0000" & ipParts(i), 4)
            Next

            result &= "Address      : " & hexa & !"\n"
            result &= "Address Space: IPv6" & !"\n"
            result &= "Port         : " & port & !"\n"
            Return result
        End If
    End If

    Return result & "Address      : Invalid Address" & !"\n"
End Function

' Test cases
Dim As String ipAddresses(0 To ...) = { _
"127.0.0.1", "127.0.0.1:80", "::1", "[::1]:80", "2605:2700:0:3::4713:93e3", _
"[2605:2700:0:3::4713:93e3]:80", "::ffff:192.168.173.22", _
"[::ffff:192.168.173.22]:80", _
"1::", "::", "256.0.0.0", "::ffff:127.0.0.0.1", "RosettaCode" }

For i As Byte = 0 To Ubound(ipAddresses)
    Print parseIP(ipAddresses(i))
Next

Sleep