Add-DbaAgListener.ps1

function Add-DbaAgListener {
    <#
    .SYNOPSIS
        Adds a listener to an availability group on a SQL Server instance.

    .DESCRIPTION
        Adds a listener to an availability group on a SQL Server instance.

    .PARAMETER SqlInstance
        The target SQL Server instance or instances. Server version must be SQL Server version 2012 or higher.

    .PARAMETER SqlCredential
        Login to the SqlInstance instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential)

    .PARAMETER AvailabilityGroup
        The Availability Group to which a listener will be bestowed upon.

    .PARAMETER Name
        The name of the listener. If one is not specified, the Availability Group name will be used.

        Note that Name cannot be used with Multiple Ags.

    .PARAMETER IPAddress
        Sets the IP address(es) of the availability group listener.

    .PARAMETER SubnetIP
        Sets the Subnet IP address(es) of the availability group listener.

    .PARAMETER SubnetMask
        Sets the subnet IP mask(s) of the availability group listener. Defaults to 255.255.255.0.

    .PARAMETER Port
        Sets the port number used to communicate with the availability group. Defaults to 1433.

    .PARAMETER Dhcp
        Indicates whether the listener uses DHCP.

    .PARAMETER Passthru
        Don't create the listener, just pass thru an object that can be further customized before creation.

    .PARAMETER InputObject
        Enables piping from Get-DbaAvailabilityGroup

    .PARAMETER WhatIf
        Shows what would happen if the command were to run. No actions are actually performed.

    .PARAMETER Confirm
        Prompts you for confirmation before executing any changing operations within the command.

    .PARAMETER EnableException
        By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
        This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting.
        Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch.

    .NOTES
        Tags: AG, HA
        Author: Chrissy LeMaire (@cl), netnerds.net

        Website: https://dbatools.io
        Copyright: (c) 2018 by dbatools, licensed under MIT
        License: MIT https://opensource.org/licenses/MIT

    .LINK
        https://dbatools.io/Add-DbaAgListener

    .EXAMPLE
        PS C:\> Add-DbaAgListener -SqlInstance sql2017 -AvailabilityGroup SharePoint -IPAddress 10.0.20.20

        Creates a listener on 10.0.20.20 port 1433 for the SharePoint availability group on sql2017.

    .EXAMPLE
        PS C:\> Get-DbaAvailabilityGroup -SqlInstance sql2017 -AvailabilityGroup availabilitygroup1 | Add-DbaAgListener -Dhcp

        Creates a listener on port 1433 with a dynamic IP for the group1 availability group on sql2017.

    .EXAMPLE
        PS C:\> Add-DbaAgListener -SqlInstance sql2017 -AvailabilityGroup SharePoint -IPAddress 10.0.20.20,10.1.77.77 -SubnetMask 255.255.252.0

        Creates a multi-subnet listener with 10.0.20.20 and 10.1.77.77, on two /22 subnets, on port 1433 for the SharePoint availability group on sql2017.
    #>
    [CmdletBinding(SupportsShouldProcess, ConfirmImpact = 'Low')]
    param (
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]$SqlCredential,
        [string[]]$AvailabilityGroup,
        [string]$Name,
        [ipaddress[]]$IPAddress,
        [ipaddress[]]$SubnetIP,
        [ipaddress[]]$SubnetMask = "255.255.255.0",
        [int]$Port = 1433,
        [switch]$Dhcp,
        [switch]$Passthru,
        [parameter(ValueFromPipeline)]
        [Microsoft.SqlServer.Management.Smo.AvailabilityGroup[]]$InputObject,
        [switch]$EnableException
    )
    process {
        if (Test-Bound -Not SqlInstance, InputObject) {
            Stop-Function -Message "You must supply either -SqlInstance or an Input Object"
            return
        }

        if ((Test-Bound -ParameterName SqlInstance) -and (Test-Bound -Not -ParameterName AvailabilityGroup)) {
            Stop-Function -Message "You must specify one or more databases and one or more Availability Groups when using the SqlInstance parameter."
            return
        }

        if ($Dhcp) {
            if (Test-Bound -ParameterName IPAddress) {
                Stop-Function -Message "You cannot specify both an IP address and the Dhcp switch."
                return
            }

            if ($SubnetMask.Count -gt 1 -or $SubnetIP.Count -gt 1) {
                Stop-Function -Message "You can only specify a single subnet when using Dhcp."
                return
            }
        }

        if ($SqlInstance) {
            $InputObject += Get-DbaAvailabilityGroup -SqlInstance $SqlInstance -SqlCredential $SqlCredential -AvailabilityGroup $AvailabilityGroup
        }

        if (Test-Bound -ParameterName IPAddress) {
            if ($IPAddress.Count -ne $SubnetMask.Count) {
                if ($SubnetMask.Count -eq 1) {
                    # If one subnet mask is supplied, let's assume we want to use the same one for every IP
                    $SubnetMask = $SubnetMask * $IPAddress.Count
                } else {
                    Stop-Function -Message "When specifying multiple IP addresses, the number of subnet masks must match, or give one mask to be used for all IP addresses."
                    return
                }
            }

            if (Test-Bound -Not -ParameterName SubnetIP) {
                # No subnets (subnet IPs) were supplied but we can calculate them with the netmask
                $SubnetIP = for ($ipIndex = 0 ; $ipIndex -lt $IPAddress.Count ; $ipIndex++) {
                    ($IPAddress[$ipIndex].Address -band $SubnetMask[$ipIndex].Address) -as [ipaddress]
                }
            } else {
                if ($IPAddress.Count -ne $SubnetIP.Count) {
                    if ($SubnetIP.Count -eq 1) {
                        # If one subnet IP is supplied, let's assume we want to use the same subnet for every IP
                        $SubnetIP = $SubnetIP * $IPAddress.Count
                    } else {
                        Stop-Function -Message "When specifying subnet IPs explicitly, the number of subnets must match the number of IPs, or use one subnet to be applied to all IPs."
                        return
                    }
                }
            }
        }

        foreach ($ag in $InputObject) {
            if ((Test-Bound -Not -ParameterName Name)) {
                $Name = $ag.Name
            }
            if ($Pscmdlet.ShouldProcess($ag.Parent.Name, "Adding $($IPAddress.IPAddressToString) to $($ag.Name)")) {
                try {
                    $aglistener = New-Object Microsoft.SqlServer.Management.Smo.AvailabilityGroupListener -ArgumentList $ag, $Name
                    $aglistener.PortNumber = $Port

                    $ipIndex = 0
                    do {
                        # add the IPs
                        $listenerip = New-Object Microsoft.SqlServer.Management.Smo.AvailabilityGroupListenerIPAddress -ArgumentList $aglistener

                        if (Test-Bound -ParameterName IPAddress) {
                            $listenerip.IPAddress = $IPAddress[$ipIndex]
                        }

                        if ($SubnetIP) {
                            $listenerip.SubnetMask = $SubnetMask[$ipIndex]
                            $listenerip.SubnetIP = $SubnetIP[$ipIndex]
                        }

                        $listenerip.IsDHCP = $Dhcp
                        $aglistener.AvailabilityGroupListenerIPAddresses.Add($listenerip)
                    } while ((++$ipIndex) -lt $IPAddress.Count)

                    if ($Passthru) {
                        return $aglistener
                    } else {
                        # something is up with .net create(), force a stop
                        Invoke-Create -Object $aglistener
                    }
                } catch {
                    Stop-Function -Message "Failure" -ErrorRecord $_
                }
                Get-DbaAgListener -SqlInstance $ag.Parent -AvailabilityGroup $ag.Name -Listener $Name
            }
        }
    }
}