AbsolutePathCssRewriteUrlTransform.cs

using System;
using System.Text.RegularExpressions;
using System.Web;
using System.Web.Optimization;

namespace Web.Extensions
{
    /// <summary>
    /// ref: http://aspnetoptimization.codeplex.com/workitem/83
    /// </summary>
    public class AbsolutePathCssRewriteUrlTransform : IItemTransform
    {
        internal static string RebaseUrlToAbsolute(string baseUrl, string url)
        {
            if (string.IsNullOrWhiteSpace(url) || string.IsNullOrWhiteSpace(baseUrl) || url.StartsWith("/", StringComparison.OrdinalIgnoreCase))
                return url;
            if (!baseUrl.EndsWith("/", StringComparison.OrdinalIgnoreCase))
                baseUrl = baseUrl + "/";
            return VirtualPathUtility.ToAbsolute(baseUrl + url);
        }

        internal static string ConvertUrlsToAbsolute(string baseUrl, string content)
        {
            if (string.IsNullOrWhiteSpace(content))
                return content;
            else
                return new Regex("url\\(['\"]?(?<url>[^)]+?)['\"]?\\)").Replace(content, (MatchEvaluator)(match => "url(" + RebaseUrlToAbsolute(baseUrl, match.Groups["url"].Value) + ")"));
        }

        public string Process(string includedVirtualPath, string input)
        {
            if (includedVirtualPath == null)
                throw new ArgumentNullException("includedVirtualPath");
            else
                return ConvertUrlsToAbsolute(VirtualPathUtility.GetDirectory(includedVirtualPath), input);
        }
    }
}