functions/Get-DbaAvailabilityGroup.ps1

function Get-DbaAvailabilityGroup {
<#
    .SYNOPSIS
        Outputs the Availability Group(s) object found on the server.
 
    .DESCRIPTION
        Default view provides most common set of properties for information on the Availability Group(s).
 
    .PARAMETER SqlInstance
        The target SQL Server instance or instances. You must have sysadmin access and server version must be SQL Server version 2012 or higher.
 
    .PARAMETER SqlCredential
        Login to the target instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential)
 
    .PARAMETER AvailabilityGroup
        Specifies the Availability Group name that you want to get information on.
 
    .PARAMETER IsPrimary
        If this switch is enabled, a boolean indicating whether SqlInstance is the Primary replica in the AG is returned.
 
    .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: Hadr, HA, AG, AvailabilityGroup
        Author: Shawn Melton (@wsmelton) | Chrissy LeMaire (@ctrlb)
 
        Website: https://dbatools.io
        Copyright: (c) 2018 by dbatools, licensed under MIT
        License: MIT https://opensource.org/licenses/MIT
 
    .LINK
        https://dbatools.io/Get-DbaAvailabilityGroup
 
    .EXAMPLE
        PS C:\> Get-DbaAvailabilityGroup -SqlInstance sqlserver2014a
 
        Returns basic information on all the Availability Group(s) found on sqlserver2014a.
 
    .EXAMPLE
        PS C:\> Get-DbaAvailabilityGroup -SqlInstance sqlserver2014a -AvailabilityGroup AG-a
 
        Shows basic information on the Availability Group AG-a on sqlserver2014a.
 
    .EXAMPLE
        PS C:\> Get-DbaAvailabilityGroup -SqlInstance sqlserver2014a | Select *
 
        Returns full object properties on all Availability Group(s) on sqlserver2014a.
 
    .EXAMPLE
        PS C:\> Get-DbaAvailabilityGroup -SqlInstance sqlserver2014a -AvailabilityGroup AG-a -IsPrimary
 
        Returns true/false if the server, sqlserver2014a, is the primary replica for AG-a Availability Group.
 
#>

    [CmdletBinding()]
    param (
        [parameter(Mandatory, ValueFromPipeline)]
        [Alias("ServerInstance", "SqlServer")]
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]$SqlCredential,
        [object[]]$AvailabilityGroup,
        [switch]$IsPrimary,
        [Alias('Silent')]
        [switch]$EnableException
    )

    process {
        foreach ($serverName in $SqlInstance) {
            try {
                $server = Connect-SqlInstance -SqlInstance $serverName -SqlCredential $SqlCredential -MinimumVersion 11
            }
            catch {
                Stop-Function -Message "Failure." -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue
            }

            if ($server.IsHadrEnabled -eq $false) {
                Stop-Function -Message "Availability Group (HADR) is not configured for the instance: $serverName." -Target $serverName -Continue
            }

            $ags = $server.AvailabilityGroups
            if ($AvailabilityGroup) {
                $ags = $ags | Where-Object Name -in $AvailabilityGroup
            }

            foreach ($ag in $ags) {
                Add-Member -Force -InputObject $ag -MemberType NoteProperty -Name ComputerName -value $server.ComputerName
                Add-Member -Force -InputObject $ag -MemberType NoteProperty -Name InstanceName -value $server.ServiceName
                Add-Member -Force -InputObject $ag -MemberType NoteProperty -Name SqlInstance -value $server.DomainInstanceName

                if ($IsPrimary) {
                    $defaults = 'ComputerName', 'InstanceName', 'SqlInstance', 'Name as AvailabilityGroup', 'IsPrimary'
                    $value = $false
                    if ($ag.PrimaryReplicaServerName -eq $server.Name) {
                        $value = $true
                    }
                    Add-Member -Force -InputObject $ag -MemberType NoteProperty -Name IsPrimary -Value $value
                    Select-DefaultView -InputObject $ag -Property $defaults
                }
                else {
                    $defaults = 'ComputerName', 'InstanceName', 'SqlInstance', 'LocalReplicaRole', 'Name as AvailabilityGroup', 'PrimaryReplicaServerName as PrimaryReplica', 'AutomatedBackupPreference', 'AvailabilityReplicas', 'AvailabilityDatabases', 'AvailabilityGroupListeners'
                    Select-DefaultView -InputObject $ag -Property $defaults
                }
            }
        }
    }
}