Sitecore Powershell Script to replace existing rendering with a new rendering

Replace-ReferencedRendering-Header.ps1

Set-Location master:

function Get-ItemBasedOnTemplate {
    param(
        [string]$TemplateId
    )

    $queue = New-Object System.Collections.Queue
    $processedLookup = New-Object System.Collections.Generic.HashSet[string]
    if(-not(Test-Path -Path "master:$($TemplateId)")) { return }
    $processedLookup.Add($TemplateId) > $null  
    Get-ItemReferrer -Id $TemplateId -ItemLink | 
        Where-Object { $_.SourceItemID } | 
        ForEach-Object { $queue.Enqueue($_.SourceItemID) }

    $database = Get-Database -Name "master"
    while($queue.Count -and ($referrerId = $queue.Dequeue())) {
        if($processedLookup.Contains($referrerId)) { continue }
        $processedLookup.Add($referrerId) > $null
        $referrer = $database.GetItem($referrerId)
        if(!$referrer) { continue }
        if($referrer.Paths.FullPath.StartsWith("/sitecore/templates")) { 
            if($referrer.Name -eq "__Standard values") { continue }
            foreach($referrerItemLink in Get-ItemReferrer -Id $referrerId -ItemLink | Where-Object { $_.SourceItemID }) {
                $queue.Enqueue($referrerItemLink.SourceItemID)
            }
            $itemTemplate = [Sitecore.Data.Managers.TemplateManager]::GetTemplate($referrerId, $database)
        } else {
            $itemTemplate = [Sitecore.Data.Managers.TemplateManager]::GetTemplate($referrer)
        }

        if ($itemTemplate -and $itemTemplate.DescendsFromOrEquals($TemplateId)) {
            $referrer
        }
    }
}

$baseTemplateId = "{68165A40-EE21-4D71-866D-4C0373FFA95E}"
$items = Get-ItemBasedOnTemplate -TemplateId $baseTemplateId

# 3 existing datasource options for the reference header
$rrHeaderId = "{7EA088EF-195D-469B-BE5F-3E5C47087F65}"
$rrHeaderTransparentId = "{14A7A8E1-24D2-4B1E-AAEC-F76DA4AD9AA9}"
$rrHeaderTransparentNoSearchId = "{A94FAE44-775D-453B-8C67-CCBA4F5D8AAE}"

$rrHeader = gi master:// -id $rrHeaderId
$rrHeaderTransparent = gi master:// -id $rrHeaderTransparentId
$rrHeaderTransparentNoSearch = gi master:// -id $rrHeaderTransparentNoSearchId

# 3 new datasource options for the new header
$newHeader = gi master:// -id "{F80A4E6D-A356-4709-8E68-4AB54F1E7C1A}"
$newHeaderTransparent = gi master:// -id "{A5390E81-6AC4-44C5-9E90-8FA255B13AA2}"
$newHeaderTransparentNoSearch = gi master:// -id "{7A84AE40-1118-427B-AE20-35187220963E}"

# rendering to use in place of existing
$newHeaderRendering = gi -Path master:\layout\Renderings\SITE\Project\Website\Sublayouts\Header | New-Rendering -Placeholder "header"
# rendering to get rid of
$referencedRendering = gi -Path "master:\layout\Renderings\SITE\Project\Website\Reference Renderings\Header Reference Rendering"

$counter = 0

foreach($i in $items){
    Write-Host "Updating " $i.Paths.Path
    $existingRendering = Get-Rendering -Item $i -Rendering $referencedRendering
    if($null -ne $existingRendering){
        $existingDatasource = $existingRendering.Datasource

        if($null -ne $existingDatasource){
           $newDatasource = switch($existingDatasource){
               $rrHeaderId { $newHeader }
               $rrHeaderTransparentId { $newHeaderTransparent }
               $rrHeaderTransparentNoSearchId { $newHeaderTransparentNoSearch }
           }
           
           # Remove the existing Header Reference Rendering
           Remove-Rendering -Item $i -Rendering $referencedRendering
           
           # Add the new header rendering to the "header" placeholder
           Add-Rendering -Item $i -Rendering $newHeaderRendering -Placeholder "header" -Datasource $newDatasource.Paths.Path
           $counter++
        }        
    }
}

Write-Host "Done! Replaced renderings on " $counter " items"