winutil/functions/private/Set-WinUtilUiTheme.ps1

function Set-WinUtilUITheme {
    <#
        .SYNOPSIS
            Sets the theme of the XAML file

        .PARAMETER inputXML
            A string representing the XAML object to modify

        .PARAMETER themeName
            The name of the theme to set the XAML to. Defaults to 'matrix'

        .EXAMPLE
            Set-WinUtilUITheme -inputXAML $inputXAML
    #>

    param
    (
         [Parameter(Mandatory, position=0)]
         [string] $inputXML,
         [Parameter(position=1)]
         [string] $themeName = 'matrix'
    )

    try {
        # Convert the JSON to a PowerShell object
        $themes = $sync.configs.themes
        # Select the specified theme
        $selectedTheme = $themes.$themeName

        if ($selectedTheme) {
            # Loop through all key-value pairs in the selected theme
            foreach ($property in $selectedTheme.PSObject.Properties) {
                $key = $property.Name
                $value = $property.Value
                # Add curly braces around the key
                $formattedKey = "{$key}"
                # Replace the key with the value in the input XML
                $inputXML = $inputXML.Replace($formattedKey, $value)
            }
        }
        else {
            Write-Host "Theme '$themeName' not found."
        }

    }
    catch {
        Write-Warning "Unable to apply theme"
        Write-Warning $psitem.Exception.StackTrace
    }

    return $inputXML;
}