function Get-ServerConfig {
    param(
        [string]$Path = ".\servers.json"
    )

    if (-not (Test-Path $Path)) {
        throw "Config-Datei nicht gefunden: $Path"
    }

    return Get-Content $Path -Raw | ConvertFrom-Json
}

function Get-ServerGroup {
    param(
        [Parameter(Mandatory)]
        [string]$Name
    )

    $config = Get-ServerConfig

    if (-not $config.groups.$Name) {
        throw "Gruppe '$Name' existiert nicht"
    }

    return $config.groups.$Name
}

function Invoke-ServerCommand {
    param(
        [Parameter(Mandatory)]
        [string]$Group,

        [Parameter(Mandatory)]
        [scriptblock]$ScriptBlock
    )

    $servers = Get-ServerGroup -Name $Group

    foreach ($server in $servers) {
        $name = $server.name

        Write-Host "[$name] Starte..." -ForegroundColor Cyan

        try {
            Invoke-Command -ComputerName $name -ScriptBlock $ScriptBlock -ErrorAction Stop
        }
        catch {
            Write-Warning "[$name] Fehler: $_"
        }
    }
}

function Invoke-ServerCommandParallel {
    param(
        [string]$Group,
        [scriptblock]$ScriptBlock
    )

    $servers = Get-ServerGroup -Name $Group

    $servers | ForEach-Object -Parallel {
        $name = $_.name

        try {
            Invoke-Command -ComputerName $name -ScriptBlock $using:ScriptBlock
        }
        catch {
            Write-Host "[$name] Fehler: $_"
        }
    }
}

Register-ArgumentCompleter -CommandName Get-ServerGroup, Invoke-ServerCommand -ParameterName Group -ScriptBlock {
    param($commandName, $parameterName, $wordToComplete)

    $config = Get-ServerConfig
    $config.groups.PSObject.Properties.Name |
        Where-Object { $_ -like "$wordToComplete*" } |
        ForEach-Object {
            [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_)
        }
}