function Get-HostnamesByEnvironmentName {

<#

.SYNOPSIS
    Retrieves the hostnames for a specified environment.

.PARAMETER EnvironmentName
    [string] The moniker associated with the environment (e.g. 'Smith', '16.1')

.PARAMETER EnvironmentType
    [string] The type associated with the environment (e.g. 'prod', 'dr').

.PARAMETER IncludeOffline
    [switch] Flag indicating whether or not to retrieve hostnames of offline instances.

.PARAMETER ProfileName
    [string] AWS profile name to use in the query.

.PARAMETER Region
    [string] AWS region to use in the query.

.EXAMPLE
    Get-HostnamesByEnvironmentName -EnvironmentName '16' -EnvironmentType 'DR' -Region 'us-west-2' -IncludeOffline -Verbose

VERBOSE: [Get-HostnamesByEnvironmentName] : Using environment value 'DR'
[Get-DesignationTagNameByEnvironment] : Checking designation value for environment DR
VERBOSE: [Get-HostnamesByEnvironmentName] : Designation value resolved to 'pod'
APP32101109
APP326418
MIC3210483
MIC327179
WEB3229114
WEB323468

.EXAMPLE
    Get-HostnamesByEnvironmentName -EnvironmentName 16 -Verbose

VERBOSE: [Get-HostnamesByEnvironmentName] : Environment type not specified; attempting to determine value.
[Get-Environment] : Environment determined to be prod based on the alk:env tag value
VERBOSE: [Get-HostnamesByEnvironmentName] : Using environment value 'prod'
[Get-DesignationTagNameByEnvironment] : Checking designation value for environment prod
VERBOSE: [Get-HostnamesByEnvironmentName] : Designation value resolved to 'pod'
APP16107240
APP1611088
APP1612031
APP16121149
APP16122255
MIC16106199
MIC16108100
MIC16117162
MIC1612736
MIC1665169
WEB162253
WEB1623247
WEB163753
WEB1647241
WEB165798
WEB166072
#>

    [OutputType([string[]])]
    [CmdletBinding()]
    param(
        [Parameter (Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [string]$EnvironmentName,

        [Parameter (Mandatory = $false)]
        [string]$EnvironmentType = $null,

        [Parameter(Mandatory = $false)]
        [switch]$IncludeOffline,

        [Parameter(Mandatory = $false)]
        [string]$ProfileName = $null,

        [Parameter(Mandatory = $false)]
        [string]$Region = $null
    )

    $logLead = (Get-LogLeadName)

    if ( [string]::IsNullOrEmpty( $EnvironmentType ) ) {
        Write-Verbose "$logLead : Environment type not specified; attempting to determine value."
        [string] $EnvironmentType = ( Get-Environment )
    }

    Write-Verbose "$logLead : Using environment value '$EnvironmentType'"

    [string] $designation = ( Get-DesignationTagNameByEnvironment $environmentType )
    Write-Verbose "$logLead : Designation value resolved to '$designation'"

    $designationTag = ( "alk:{0}" -f $designation )

    $searchTags = @{
        $designationTag                 = $EnvironmentName
        $Global:AlkamiTagKeyEnvironment = $EnvironmentType.ToLowerInvariant()
    }

    [Amazon.EC2.Model.Instance[]] $Instances = Get-InstancesByTag -tags $searchTags -IncludeOffline:$IncludeOffline -ProfileName $ProfileName -Region $Region

    [string[]] $hostNames = @()
    foreach ( $instance in $instances ) {

        $hostname = Get-InstanceHostname $instance

        if ( ! [string]::IsNullOrEmpty( $hostname ) ) {
            $hostNames += $hostname
        }
    }

    [Array]::Sort($hostNames)
    return $hostNames
}