Set-CloudflareDynamicIpAddress.ps1

[CmdletBinding()]
param(
    [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
    [string[]]$Hostname,

    [Parameter()]
    [string]$CloudflareEmail = "$env:CLOUDFLARE_EMAIL",

    [Parameter()]
    [string]$CloudflareApiKey = "$env:CLOUDFLARE_APIKEY"
)

Begin {
    if ([string]::IsNullOrWhiteSpace($CloudflareEmail)) {
        Write-Error "You must provide a Cloudflare email address" -ErrorAction Stop
    }
    
    if ([string]::IsNullOrWhiteSpace($CloudflareApiKey)) {
        Write-Error "You must provide a Cloudflare API key" -ErrorAction Stop
    }

    $headers = @{
        'X-Auth-Email' = $CloudflareEmail;
        'X-Auth-Key' = $CloudflareApiKey;
        'Content-Type' = 'application/json'
    }

    $cloudflaseBaseUri = 'https://api.cloudflare.com/client/v4'
}

Process {
    foreach ($h in $Hostname) {
        $parts = $h.Split('.')
        $zoneName = "{0}.{1}" -f $parts[-2], $parts[-1]

        # lookup dns zone
        $response = Invoke-RestMethod -Method Get -Headers $headers -Uri "$cloudflaseBaseUri/zones?name=$([uri]::EscapeDataString($zoneName))" -ErrorAction Stop

        if ($response.result_info.count -ne 1) {
            Write-Error "Unable to find a DNS zone for '$zoneName'" -ErrorAction Stop
        }
        $zone = $response.result

        # lookup dns record for hostname
        $dnsRecordsUri = "$cloudflaseBaseUri/zones/$($zone.id)/dns_records"

        $response = Invoke-RestMethod -Method Get -Headers $headers -Uri $dnsRecordsUri

        $record = $response.result | Where-Object name -eq $h
        if ($null -eq $record) {
            Write-Error "Unable to find record for '$h'" -ErrorAction Stop
        }

        if ($record.type -ne 'A') {
            Write-Error "'$h' must point to an 'A' record." -ErrorAction Stop
        }

        $ip = Invoke-RestMethod https://diagnostic.opendns.com/myip
        if ($record.content -eq $ip) {
            Write-Host "IP address for '$h' has not changed [$ip]"
        } else {
            Write-Host "IP address for '$h' has changed from '$($record.content)' to '$ip'."

            $body = @{
                "type" = $record.type;
                "name" = $record.name;
                "content" = $ip;
            } | ConvertTo-Json

            $response = Invoke-RestMethod -Method PUT -Headers $headers -Uri "$dnsRecordsUri/$($record.id)" -Body $body
            if (-not $response.success) {
                Write-Error "There was an error updating the IP address for '$h'`n`n$($response | ConvertTo-Json)"
            }
        }
    }
}