Trying to respond to a Slack PM with a response including buttons

Invoke-ExampleSlackBot

Function Invoke-ExampleSlackBot {
    [cmdletbinding()]
    Param(
        [Parameter(Mandatory=$true,ValueFromPipelineByPropertyName=$true)]
            [ValidateNotNullOrEmpty()]
            [string]$BotName,
        [Parameter(Mandatory=$false,ValueFromPipelineByPropertyName=$true)]
            [ValidateNotNullOrEmpty()]
            [securestring]$Token = $(Read-Host -Prompt "API Key" -AsSecureString)
    )
    
    
    $ClearToken = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto(
        [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR(
            $Token
        )
    )

    #Web API call starts the session and gets a websocket URL to use.
    $RTMSession = Invoke-RestMethod -Uri https://slack.com/api/rtm.start -Body @{token="$ClearToken"}
    Write-Verbose "I am $($RTMSession.self.name)"

    Try{
        Do{
            $WS = New-Object System.Net.WebSockets.ClientWebSocket                                                
            $CT = New-Object System.Threading.CancellationToken                                                   

            $Conn = $WS.ConnectAsync($RTMSession.URL, $CT)                                                  
            While (!$Conn.IsCompleted) { Start-Sleep -Milliseconds 100 }

           Write-Verbose "Connected to $($RTMSession.URL)"

            $Size = 1024
            $Array = [byte[]] @(,0) * $Size
            $Recv = New-Object System.ArraySegment[byte] -ArgumentList @(,$Array)

            While ($WS.State -eq 'Open') {

                $RTM = ""

                Do {
                    $Conn = $WS.ReceiveAsync($Recv, $CT)
                    While (!$Conn.IsCompleted) { Start-Sleep -Milliseconds 100 }

                    $Recv.Array[0..($Conn.Result.Count - 1)] | ForEach-Object { $RTM = $RTM + [char]$_ }

                } Until ($Conn.Result.Count -lt $Size)

                Write-Verbose "$RTM"

                If ($RTM){
                    $RTM = ($RTM | convertfrom-json)

                    Switch ($RTM){
                        {($_.type -eq 'message') -and (!$_.reply_to)} { 

                            If ( ($_.text -Match "<@$($RTMSession.self.id)>") -or $_.channel.StartsWith('D') ){
                                #A message was sent to the bot

                                $MessageCommand = @{
                                    BotName = $BotName
                                    Message = "$($_.text)".ToLower()
                                    Channel = $RTM.Channel
                                }

                                if ($MessageCommand.Message){
                                    
                                    $ID = (get-date).ticks
                                    $Timeout = 30

                                    $Prop = @{
                                        'id'      = $ID;
                                        'type'    = 'message';
                                        'text'    = 'Would you like to play a game?';
                                        'channel' = $MessageCommand.Channel
                                        'attachments' = @(
                                            @{
                                                "text" =  "Choose a game to play"
                                                "fallback" = "You are unable to choose a game"
                                                "callback_id" = "wopr_game"
                                                "color" = "#3AA3E3"
                                                "attachment_type" = "default"
                                                "actions" =  @(
                                                    @{
                                                        "name" = "game"
                                                        "text" = "Chess"
                                                        "type" = "button"
                                                        "value" = "chess"
                                                    },
                                                    @{
                                                        "name" = "game"
                                                        "text" = "Falken's Maze"
                                                        "type" = "button"
                                                        "value" = "maze"
                                                    },
                                                    @{
                                                        "name" = "game"
                                                        "text" = "Thermonuclear War"
                                                        "style" = "danger"
                                                        "type" = "button"
                                                        "value" = "war"
                                                        "confirm" = @{
                                                            "title" = "Are you sure?"
                                                            "text" = "Wouldn't you prefer a good game of chess?"
                                                            "ok_text" = "Yes"
                                                            "dismiss_text" = "No"
                                                        }
                                                    }
                                                )
                                            }
                                        )
                                    }
    
                                    $Msg = (New-Object –TypeName PSObject –Prop $Prop) | ConvertTo-Json -Depth 5


									$Array = @()
									$Msg.ToCharArray() | ForEach-Object { $Array = $Array + [byte]$_ }
                                    
                                    Write-Verbose $msg

									$Msg = New-Object System.ArraySegment[byte]  -ArgumentList @(,$Array)
                                    
                                    Write-Verbose $msg

									$Conn = $WS.SendAsync($Msg, [System.Net.WebSockets.WebSocketMessageType]::Text, [System.Boolean]::TrueString, $CT)
									$ConnStart = Get-Date

									While (!$Conn.IsCompleted) { 
										$TimeTaken = ((get-date) - $ConnStart).Seconds
										If ($TimeTaken -gt $Timeout) {
											Write-Verbose -Level Error "Message $ID took longer than $Timeout seconds and may not have been sent."
											Return
										}
										Start-Sleep -Milliseconds 100 
									}
									
                                }

                            }Else{
                                Write-Verbose "Message ignored as it wasn't sent to @$($RTMSession.self.name) or in a DM channel"
                            }
                        }
                        {$_.type -eq 'reconnect_url'} { $RTMSession.URL = $RTM.url }

                        default { Write-Verbose "No action specified for $($RTM.type) event" }
                    }
                }
            }   
        } Until (!$Conn)

    }Finally{

        If ($WS) { 
            Write-Verbose "Closing websocket"
            $WS.Dispose()
        }

    }

}

Invoke-ExampleSlackBot -BotName ProtobotSlack

See:

• https://api.slack.com/interactive-messages
• https://github.com/markwragg/Powershell-SlackBot