using System;
using System.Web;

public class ReWriteModule : IHttpModule
{
    public ReWriteModule()
    {
    }
    public override string ToString()
    {
        return this.GetType().ToString();
    }

    void IHttpModule.Dispose()
    {
    }
    private static System.Xml.XmlDocument ruleDoc = null;
    private static System.Xml.XmlDocument GetRuleConfig(System.Web.HttpContext app)
    {
        if (ruleDoc == null)
        {
            ruleDoc = new System.Xml.XmlDocument();
            ruleDoc.Load(app.Server.MapPath("~/rule.xml"));
        }
        return ruleDoc;
    }
    public static string GetUrl(System.Web.HttpContext cxt, string path)
    {
        System.Xml.XmlDocument doc = GetRuleConfig(cxt);
        System.Xml.XmlNodeList lst = doc.GetElementsByTagName("RewriterRule");
        string pat = "";
        foreach (System.Xml.XmlNode nd in lst)
        {
            System.Xml.XmlNodeList sub = nd.ChildNodes[0].ChildNodes;
            foreach (System.Xml.XmlNode chk in sub)
            {
                pat = "^" + chk.InnerText + "$";
                System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex(pat, System.Text.RegularExpressions.RegexOptions.Compiled | System.Text.RegularExpressions.RegexOptions.IgnoreCase);
                if (reg.IsMatch(path))
                {
                    return reg.Replace(path, nd.ChildNodes[1].InnerText);
                }
            }
        }
        return null;
    }

    void IHttpModule.Init(HttpApplication context)
    {
        context.BeginRequest += delegate(object sender, EventArgs e)
        {
            System.Web.HttpContext cxt = context.Context;

            if (cxt.Request.ContentType != "image/pjpeg")
            {
                string type = cxt.Request.ContentType.ToLower();
                string path = cxt.Request.Path;
                string apppath = cxt.Request.ApplicationPath;
                path = path.Remove(0, apppath.Length);
                path = "~" + path;

                string newUrl = GetUrl(cxt, path.TrimEnd().TrimStart());
                if (newUrl != null)
                {
                    cxt.Response.Filter = new ResponseFilter(cxt.Response.Filter, cxt.Request.Path);
                    cxt.Response.Write("请求的路径:" + path);
                    cxt.Response.Write("");
                    cxt.Response.Write("转向的目的URL：" + newUrl);
                    cxt.Response.Write("");
                    cxt.RewritePath(newUrl);
                }
  //如果要求处理所有的请求时用到
                //else
                //{
                // cxt.Response.Write(cxt.Request.Path + "");
                // cxt.Response.Write("你请求的资源不存在或无权访问！");
                // cxt.Response.Flush();
                // cxt.Response.End();
                //}
            }
        };
    }
}