Converts a string to an RFC 4122 compatible UUID.

ConvertTo-Guid.ps1

function SwapBytes {
    <#
        .SYNOPSIS
            Simply switches two bytes in an array of bytes
    #>
    param(
        [Parameter(Mandatory)]
        [byte[]]$Guid,
        [Parameter(Mandatory)]
        [int]$Left,
        [Parameter(Mandatory)]
        [int]$Right
    )
    $Guid[$Left], $Guid[$Right] = $Guid[$Right], $Guid[$Left]
}

function SwapByteOrder {
    <#
        .SYNOPSIS
            Convert between Local and Network order
    #>
    param(
        [byte[]]$Guid
    )
    SwapBytes $Guid 0 3
    SwapBytes $Guid 1 2
    SwapBytes $Guid 4 5
    SwapBytes $Guid 6 7
}

function ConvertTo-Guid {
    <#
        .Synopsis
            Converts a string (or bytes) into a deterministic GUID, based on a specific namespace

        .Link
            https://www.ietf.org/rfc/rfc4122.txt
            RFC

        .Link
            https://github.com/Faithlife/FaithlifeUtility/blob/master/src/Faithlife.Utility/GuidUtility.cs
            Original by Bradley Grainger

        .Example
            ConvertTo-Guid 'env.CCR_Api_Key'
    #>
    [CmdletBinding(DefaultParameterSetName="FromString")]
    param(
        [Parameter(Mandatory, Position=0, ParameterSetName = "FromString")]
        [string]$String,

        [Parameter(Mandatory, ParameterSetName = "FromBytes")]
        [byte[]]$Bytes = $([System.Text.Encoding]::UTF8.GetBytes($String)), 

        [ValidateSet(
            "6ba7b810-9dad-11d1-80b4-00c04fd430c8",  # DnsNamespace
            "6ba7b811-9dad-11d1-80b4-00c04fd430c8",  # UrlNamespace
            "6ba7b812-9dad-11d1-80b4-00c04fd430c8",  # IsoOidNamespace
            "361E6D51-FAEC-444A-9079-341386DA8E2E"   # Ansible, should be v5
        )]
        [guid]$NamespaceId = "361E6D51-FAEC-444A-9079-341386DA8E2E",

        [ValidateSet(3,5)]
        $Version = 5
    )
    process {
        # Convert the namespace UUID to network order (step 3)
        $NamespaceBytes = $NamespaceId.ToByteArray()
        SwapByteOrder $NamespaceBytes

        # Compute the hash of the namespace ID concatenated with the name (step 4)
        $Data = $NamespaceBytes + $Bytes
        [byte[]]$Hash = switch ($Version) {
            3 { [System.Security.Cryptography.MD5]::Create().ComputeHash($Data) }
            5 { [System.Security.Cryptography.SHA1]::Create().ComputeHash($Data) }
        }

        $NewGuid = [byte[]]$Hash[0..15]

        # Set the four most significant bits (bits 12 through 15) of the time_hi_and_version field
        # to the appropriate 4-bit version number from Section 4.1.3 (step 8)
        $NewGuid[6] = $NewGuid[6] -band 0x0F -bor $Version -shl 4

        # Set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to
        # zero and one, respectively (step 10)
        $NewGuid[8] = $NewGuid[8] -band 0x3F -bor 0x80

        SwapByteOrder($NewGuid)

        [Guid]$NewGuid
    }
}