$hetznerCredentials = Get-Credential

$nodeList = docker node ls --format '{{json .}}'| ConvertFrom-Json | ForEach-Object {
    docker node inspect $_.ID | ConvertFrom-Json
}
$onlineNodeList = $nodeList | Where-Object {$_.Spec.Availability -eq 'active'}

if (!($nodeList | Where-Object {$_.Spec.Availability -ne 'active'})) {
    Write-Output 'all hosts online, nothing to failover'
    exit
}

$failoverAddressList = (Invoke-RestMethod -Uri 'https://robot-ws.your-server.de/failover' -Authentication Basic -Credential $hetznerCredentials).failover
$onlineNodeAddressList = $onlineNodeList.Description.Hostname | ForEach-Object {
    dig +short $_
}
$offlineAddressList = $failoverAddressList | Where-Object active_server_ip -notin $onlineNodeAddressList

$maximumAddressCount = [Math]::Ceiling($failoverAddressList.Count / $onlineNodeList.Count)

$i = 0
$addressGroupList = $onlineNodeAddressList
| ForEach-Object {
    $nodeAddress = $_
    @{
        Count = [int]($addressGroupList | Where-Object {$_.Name -eq $nodeAddress}).Count
        NodeAddress = $nodeAddress
    }
}
| Sort-Object Count
$distributionTarget = :distribution foreach ($addressGroup in $addressGroupList) {
    $currentAddressCount = $addressGroup.Count - 1

    while ($currentAddressCount -lt $maximumAddressCount) {
        if (!$offlineAddressList[$i]) {
            # abort when all addresses are assigned
            break distribution
        }

        @{
            active_server_ip = $addressGroup.NodeAddress
            ip = $offlineAddressList[$i++].ip
            node = (dig +short -x $($addressGroup.NodeAddress)) -replace '\.$'
        }
        $currentAddressCount++
    }
}

# docker label updates must not run in parallel to prevent out-of-sequence errors
$distributionTarget | ForEach-Object {
    # first add the new labels and afterwards remove the old ones
    # this prevents situations where no host has the label anymore
    $labelName = 'link.lubi.ip.'+$_.ip

    $filter = 'node.label='+$labelName
    $cleanupNodeList = docker node ls --filter $filter --format '{{json .}}' | ConvertFrom-Json

    $label = $labelName+'=true'
    docker node update --label-add $label $($_.node)

    $cleanupNodeList | ForEach-Object {
        docker node update --label-rm $labelName $($_.ID)
    }
}
$distributionTarget | ForEach-Object -ThrottleLimit $failoverAddressList.Count -Parallel {
    Invoke-RestMethod -Method Post -Uri ('https://robot-ws.your-server.de/failover/{0}' -f $_.ip) -Authentication Basic -Credential $using:hetznerCredentials -Body @{active_server_ip=$_.active_server_ip}
}