/* 
* 
* 防盗链IHttpHandler 
* 
* 
* 增加了对文件关键字的选择(即仅对文件名存在某些关键字或不存在某些关键字进行过滤) 
* 设置web.config中<appSettings>节以下值 
* string eWebapp_NoLink 如果文件名符合该正确表态式将进行过滤(不设置对所有进行过滤) 
* string eWebapp_AllowLink 如果文件名符合该正确表态式将不进行过滤(优先权高于AllowLink,不设置则服从AllowLink) 
* bool eWebapp_ AllowOnlyFile 如果为False,(默认true)则不允许用户直接对该文件进行访问建议为true 
* 
* 
* :)以下设置均可省略,设置只是为了增加灵活性与体验 
* eWebapp_NoLink_Message 错误信息提示:默认为Link From:域名 
* eWebapp_Error_Width 错误信息提示图片宽 
* eWebapp_Error_Height 错误信息提示图片高 
* 
* 
* 
* 垃圾猪 2005-9-11 创建 
* http://ewebapp.net 
*/

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Configuration;
using System.Text.RegularExpressions;

namespace eWebapp
{
    /// <summary> 
    /// 防盗链IHttpHandler 
    /// 参考http://www.softat.org/archiver/tid-52114.html 
    /// 垃圾猪 2005-9-12 修正 
    /// </summary> 
    public class NoLink : IHttpHandler
    {
        private string eWebapp_NoLink = string.Empty;
        private string eWebapp_AllowLink = string.Empty;
        private bool eWebapp_AllowOnlyFile = true;

        private string eWebapp_NoLink_Message = string.Empty;
        private bool error = false;

        public NoLink()
        {
            // 
            // TODO: 在此处添加构造函数逻辑 
            // 
        }

        public void ProcessRequest(HttpContext context)
        {
            eWebapp_NoLink_Message = ConfigurationSettings.AppSettings["eWebapp_NoLink_Message"];

            string myDomain = string.Empty;

            error = errorLink(context, out myDomain);

            if (Empty(eWebapp_NoLink_Message))
            {
                eWebapp_NoLink_Message = "Link from :" + myDomain;
            }

            if (error)
            {
                //Jpg(context.Response,eWebapp_NoLink_Message); 
                Jpg(context.Response, eWebapp_NoLink_Message);
            }
            else
            {
                Real(context.Response, context.Request);
            }

        }

        public bool IsReusable
        {
            get
            {
                return true;
            }
        }

        /// <summary> 
        /// 输出错误信息 
        /// </summary> 
        /// <param name="Response"></param> 
        /// <param name="_word"></param> 
        private void Jpg(HttpResponse Response, string _word)
        {

            int myErrorWidth = _word.Length * 15;
            int myErrorHeight = 16;
            try
            {
                int _myErrorWidth = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Width"]);
                if (_myErrorWidth > 0)
                {
                    myErrorWidth = _myErrorWidth;
                }

            }
            catch
            {

            }
            try
            {
                int _myErrorHeight = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Height"]);
                if (_myErrorHeight > 0)
                {
                    myErrorHeight = _myErrorHeight;
                }
            }
            catch
            {

            }
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            Img = new Bitmap(myErrorWidth, myErrorHeight);
            g = Graphics.FromImage(Img);
            g.Clear(Color.White);
            Font f = new Font("Arial", 9);
            SolidBrush s = new SolidBrush(Color.Red);
            g.DrawString(_word, f, s, 3, 3);
            ms = new MemoryStream();
            Img.Save(ms, ImageFormat.Jpeg);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());