param(
    [Parameter(Mandatory = $true)]
    [Alias('WebUrl')]
    [string]$SiteUrl,

    [string]$CssPath = '',

    [string[]]$AllowedCssHost = @(),

    [switch]$EnableDebug,

    [switch]$Disable,

    [switch]$ResetConfiguration,

    [string]$ClassicScriptUrl = '',

    [switch]$RemoveClassicScriptLink,

    [string]$Description = 'MSFT-Custom-Solution:CustomBranding'
)

if (-not (Get-Command -Name Get-SPSite -ErrorAction SilentlyContinue)) {
    if (Get-Module -ListAvailable -Name Microsoft.SharePoint.PowerShell) {
        Import-Module Microsoft.SharePoint.PowerShell -DisableNameChecking
    }
    elseif (Get-PSSnapin -Registered -Name Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue) {
        Add-PSSnapin Microsoft.SharePoint.PowerShell
    }
    else {
        throw 'Die SharePoint PowerShell-Komponenten wurden nicht gefunden. Bitte in der SharePoint Management Shell ausfuehren.'
    }
}

$componentId = [Guid]'035ba968-6488-4d42-86b3-0470ffcc95b9'
$componentIdText = $componentId.ToString().ToLowerInvariant()
$componentLocation = 'ClientSideExtension.ApplicationCustomizer'
$componentName = 'CustomBranding'
$componentTitle = 'Custom Branding Application Customizer'
$classicActionName = 'CustomBranding.Classic.ScriptLink'

function New-DefaultCustomBrandingConfiguration {
    return @{
        schemaVersion = 2
        enabled = $true
        debug = $false
        allowedCssHosts = @()
        cssfiles = @()
        placeholdertop = @{ elements = @() }
        placeholderbottom = @{ elements = @() }
    }
}

function ConvertTo-Hashtable {
    param([object]$InputObject)
    if ($null -eq $InputObject) { return $null }
    if ($InputObject -is [System.Collections.IDictionary]) {
        $result = @{}
        foreach ($key in $InputObject.Keys) { $result[$key] = ConvertTo-Hashtable $InputObject[$key] }
        return $result
    }
    if ($InputObject -is [System.Collections.IEnumerable] -and -not ($InputObject -is [string])) {
        return @($InputObject | ForEach-Object { ConvertTo-Hashtable $_ })
    }
    if ($InputObject.PSObject -and $InputObject.PSObject.Properties.Count -gt 0 -and
        -not ($InputObject -is [string]) -and -not ($InputObject.GetType().IsPrimitive)) {
        $result = @{}
        foreach ($property in $InputObject.PSObject.Properties) { $result[$property.Name] = ConvertTo-Hashtable $property.Value }
        return $result
    }
    return $InputObject
}

function Get-ExistingConfiguration {
    param([Microsoft.SharePoint.SPUserCustomAction]$Action)
    if ($ResetConfiguration -or -not $Action -or [string]::IsNullOrWhiteSpace($Action.ClientSideComponentProperties)) {
        return New-DefaultCustomBrandingConfiguration
    }
    try {
        $parsed = $Action.ClientSideComponentProperties | ConvertFrom-Json
        $configuration = ConvertTo-Hashtable $parsed
        if (-not $configuration) { return New-DefaultCustomBrandingConfiguration }
        return $configuration
    }
    catch {
        Write-Warning 'Vorhandene ClientSideComponentProperties waren ungueltig und werden durch Standardwerte ersetzt.'
        return New-DefaultCustomBrandingConfiguration
    }
}

function Remove-WebScopedComponentActions {
    param([Microsoft.SharePoint.SPSite]$CurrentSite)
    $removed = 0
    foreach ($web in $CurrentSite.AllWebs) {
        try {
            $actions = @($web.UserCustomActions | Where-Object {
                $_.Location -eq $componentLocation -and
                $_.ClientSideComponentId -and
                $_.ClientSideComponentId.ToString().ToLowerInvariant() -eq $componentIdText
            })
            foreach ($action in $actions) {
                $action.Delete()
                $removed++
            }
            if ($actions.Count -gt 0) { $web.Update() }
        }
        finally {
            $web.Dispose()
        }
    }
    return $removed
}

$site = Get-SPSite -Identity $SiteUrl
try {
    $siteActions = @($site.UserCustomActions | Where-Object {
        $_.Location -eq $componentLocation -and
        $_.ClientSideComponentId -and
        $_.ClientSideComponentId.ToString().ToLowerInvariant() -eq $componentIdText
    })
    $action = $siteActions | Select-Object -First 1
    $configuration = Get-ExistingConfiguration -Action $action

    $configuration.schemaVersion = 2
    if (-not $configuration.ContainsKey('placeholdertop')) { $configuration.placeholdertop = @{ elements = @() } }
    if (-not $configuration.ContainsKey('placeholderbottom')) { $configuration.placeholderbottom = @{ elements = @() } }
    if (-not $configuration.ContainsKey('cssfiles')) { $configuration.cssfiles = @() }
    if (-not $configuration.ContainsKey('allowedCssHosts')) { $configuration.allowedCssHosts = @() }
    if ($PSBoundParameters.ContainsKey('EnableDebug')) { $configuration.debug = [bool]$EnableDebug.IsPresent }
    if ($PSBoundParameters.ContainsKey('Disable')) { $configuration.enabled = -not [bool]$Disable.IsPresent }

    if (-not [string]::IsNullOrWhiteSpace($CssPath)) {
        $trimmedPath = $CssPath.Trim()
        $existingPaths = @($configuration.cssfiles | ForEach-Object {
            if ($_ -is [System.Collections.IDictionary]) { [string]$_['path'] } else { [string]$_.path }
        })
        if ($existingPaths -notcontains $trimmedPath) {
            $configuration.cssfiles = @($configuration.cssfiles) + @(@{ path = $trimmedPath; media = 'all' })
        }
    }
    if ($AllowedCssHost.Count -gt 0) {
        $configuration.allowedCssHosts = @($AllowedCssHost | ForEach-Object { $_.Trim().ToLowerInvariant() } | Where-Object { $_ } | Select-Object -Unique)
    }

    if (-not $action) {
        $action = $site.UserCustomActions.Add()
        Write-Host 'Erstelle zentrale CustomBranding Site-Collection-Action...' -ForegroundColor Yellow
    }
    else {
        Write-Host 'Aktualisiere zentrale CustomBranding Site-Collection-Action...' -ForegroundColor Yellow
    }
    $action.Name = $componentName
    $action.Title = $componentTitle
    $action.Description = $Description
    $action.Location = $componentLocation
    $action.Sequence = 100
    $action.ClientSideComponentId = $componentId
    $action.ClientSideComponentProperties = [string]($configuration | ConvertTo-Json -Depth 20 -Compress)
    $action.Update()

    @($siteActions | Select-Object -Skip 1) | ForEach-Object {
        Write-Host ('Entferne doppelte Site-Collection-Action: ' + $_.Id) -ForegroundColor Yellow
        $_.Delete()
    }
    $removedWebActions = Remove-WebScopedComponentActions -CurrentSite $site

    $classicActions = @($site.UserCustomActions | Where-Object {
        $_.Location -eq 'ScriptLink' -and $_.Name -eq $classicActionName
    })
    if ($RemoveClassicScriptLink) {
        foreach ($classicAction in $classicActions) { $classicAction.Delete() }
        Write-Host 'Classic ScriptLink wurde entfernt.' -ForegroundColor Yellow
    }
    elseif (-not [string]::IsNullOrWhiteSpace($ClassicScriptUrl)) {
        $classicAction = $classicActions | Select-Object -First 1
        if (-not $classicAction) { $classicAction = $site.UserCustomActions.Add() }
        $classicAction.Name = $classicActionName
        $classicAction.Title = 'CustomBranding Classic Runtime'
        $classicAction.Description = $Description
        $classicAction.Location = 'ScriptLink'
        $classicAction.Sequence = 101
        $classicAction.ScriptSrc = $ClassicScriptUrl.Trim()
        $classicAction.Update()
        @($classicActions | Select-Object -Skip 1) | ForEach-Object { $_.Delete() }
        Write-Host ('Classic ScriptLink: ' + $classicAction.ScriptSrc) -ForegroundColor Green
    }

    Write-Host 'CustomBranding wurde zentral fuer die Site Collection registriert.' -ForegroundColor Green
    Write-Host ('Entfernte web-scoped Actions: ' + $removedWebActions)
    Write-Host ('Properties: ' + $action.ClientSideComponentProperties)
}
finally {
    if ($site) { $site.Dispose() }
}