[CmdletBinding(SupportsShouldProcess = $true)]
param(
    [Parameter(Mandatory = $true)]
    [string]$SiteUrl,

    [Parameter(Mandatory = $true)]
    [string]$ListTitle,

    [Parameter(Mandatory = $true)]
    [string]$ExpiryFieldInternalName,

    [Guid]$FieldCustomizerComponentId = 'a555f4fc-d6a6-4421-8189-457449d9bbde',

    [switch]$RemoveClassicWebScriptLink
)

$isapiPath = Join-Path ([Environment]::GetFolderPath('CommonProgramFiles')) 'microsoft shared\Web Server Extensions\16\ISAPI'
Add-Type -Path (Join-Path $isapiPath 'Microsoft.SharePoint.Client.Runtime.dll')
Add-Type -Path (Join-Path $isapiPath 'Microsoft.SharePoint.Client.dll')

function Expand-ExpiryIndicatorBindings {
    param([object]$Value)

    if ($null -eq $Value) { return }
    if ($Value -is [System.Array]) {
        foreach ($item in $Value) {
            Expand-ExpiryIndicatorBindings -Value $item
        }
        return
    }
    if ($Value.PSObject.Properties['webUrl'] -and
        $Value.PSObject.Properties['listId'] -and
        $Value.PSObject.Properties['fieldInternalName']) {
        Write-Output $Value
    }
}

$context = New-Object Microsoft.SharePoint.Client.ClientContext($SiteUrl)
$context.Credentials = [System.Net.CredentialCache]::DefaultNetworkCredentials

try {
    $list = $context.Web.Lists.GetByTitle($ListTitle)
    $field = $list.Fields.GetByInternalNameOrTitle($ExpiryFieldInternalName)
    $rootWeb = $context.Site.RootWeb
    $customActions = $list.UserCustomActions
    $webCustomActions = $context.Web.UserCustomActions
    $context.Load($list)
    $context.Load($field)
    $context.Load($context.Web)
    $context.Load($rootWeb)
    $context.Load($rootWeb.AllProperties)
    $context.Load($customActions)
    $context.Load($webCustomActions)
    $context.ExecuteQuery()

    if ($field.ClientSideComponentId -ne $FieldCustomizerComponentId) {
        throw "Das Feld '$($field.InternalName)' ist nicht mit dem erwarteten ExpiryIndicator-Field-Customizer verbunden."
    }

    if ($PSCmdlet.ShouldProcess("$($list.Title)/$($field.InternalName)", 'Field-Customizer-Verknüpfung entfernen')) {
        $field.ClientSideComponentId = [Guid]::Empty
        $field.ClientSideComponentProperties = ''
        $field.Update()

        $bindingsKey = 'PortalSettings.ExpiryIndicator.Bindings'
        $bindings = @()
        $existingBindingsJson = [string]$rootWeb.AllProperties[$bindingsKey]
        if (-not [string]::IsNullOrWhiteSpace($existingBindingsJson)) {
            try {
                $parsedBindings = $existingBindingsJson | ConvertFrom-Json
                $bindings = @(Expand-ExpiryIndicatorBindings -Value $parsedBindings)
            }
            catch {
                $bindings = @()
            }
        }
        $webUrl = $context.Web.Url.TrimEnd('/')
        $listId = $list.Id.ToString('D')
        $bindings = @($bindings | Where-Object {
            -not (
                ([string]$_.webUrl).TrimEnd('/').Equals($webUrl, [StringComparison]::OrdinalIgnoreCase) -and
                ([string]$_.listId).Equals($listId, [StringComparison]::OrdinalIgnoreCase)
            )
        })
        $rootWeb.AllProperties[$bindingsKey] = (ConvertTo-Json -InputObject @($bindings) -Compress -Depth 5)
        $rootWeb.Update()

        $customActions | Where-Object {
            $_.Name -eq 'ExpiryIndicator.Classic.ScriptLink' -or
            $_.Name -eq 'ExpiryIndicator.Classic.Ribbon'
        } | ForEach-Object {
            $_.DeleteObject()
        }

        if ($RemoveClassicWebScriptLink) {
            $webCustomActions | Where-Object {
                $_.Name -eq 'ExpiryIndicator.Classic.ScriptLink'
            } | ForEach-Object {
                $_.DeleteObject()
            }
        }

        $context.ExecuteQuery()
        Write-Host 'ExpiryIndicator-Verknüpfung und listenspezifische Classic-Registrierungen wurden entfernt. Feld und Daten bleiben unverändert.'
        if (-not $RemoveClassicWebScriptLink) {
            Write-Host 'Der gemeinsam verwendete Classic-Web-ScriptLink bleibt bestehen. Verwende -RemoveClassicWebScriptLink, wenn keine weitere Liste ihn benötigt.'
        }
    }
}
finally {
    $context.Dispose()
}