/BlogEngine/BlogEngine.NET/App_Code/Controls/SearchOnSearch.cs

// --------------------------------------------------------------------------------------------------------------------

// <summary>

//   If the visitor arrives through a search engine, this control

//   will display an in-site search result based on the same search term.

// </summary>

// --------------------------------------------------------------------------------------------------------------------



namespace App_Code.Controls

{

    using System.Collections.Generic;

    using System.Text;

    using System.Text.RegularExpressions;

    using System.Web;

    using System.Web.UI;



    using BlogEngine.Core;



    /// <summary>

    /// If the visitor arrives through a search engine, this control

    ///     will display an in-site search result based on the same search term.

    /// </summary>

    public class SearchOnSearch : Control

    {

        #region Constants and Fields



        /// <summary>

        /// The rx search term.

        /// </summary>

        private static readonly Regex RxSearchTerm;



        #endregion



        #region Constructors and Destructors



        /// <summary>

        /// Initializes static members of the <see cref="SearchOnSearch"/> class.

        /// </summary>

        static SearchOnSearch()

        {

            // Matches the query string parameter "q" and its value.  Does not match if "q" is blank.

            RxSearchTerm = new Regex(

                "[?&]q=([^&#]+)", RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

        }



        #endregion



        #region Properties



        /// <summary>

        ///     Gets or sets the text of the headline.

        /// </summary>

        public string Headline { get; set; }



        /// <summary>

        ///     Gets or sets the maximum numbers of results to display.

        /// </summary>

        public int MaxResults { get; set; }



        /// <summary>

        ///     Gets or sets the text displayed below the headline.

        /// </summary>

        public string Text { get; set; }



        /// <summary>

        ///     Gets a value indicating whether the referrer is from a search engine.

        /// </summary>

        private bool IsSearch

        {

            get

            {

                if (this.Context.Request.UrlReferrer != null)

                {

                    var referrer = this.Context.Request.UrlReferrer.ToString().ToLowerInvariant();

                    return RxSearchTerm.IsMatch(referrer);

                }



                return false;

            }

        }



        #endregion



        #region Public Methods



        /// <summary>

        /// Renders the control as a script tag.

        /// </summary>

        /// <param name="writer">

        /// The writer.

        /// </param>

        public override void RenderControl(HtmlTextWriter writer)

        {

            var html = this.Html();

            if (html != null)

            {

                writer.Write(html);

            }

        }



        #endregion



        #region Methods



        /// <summary>

        /// Retrieves the search term from the specified referrer string.

        /// </summary>

        /// <param name="referrer">

        /// The referrer.

        /// </param>

        /// <returns>

        /// The get search term.

        /// </returns>

        private static string GetSearchTerm(string referrer)

        {

            var term = string.Empty;

            var match = RxSearchTerm.Match(referrer);



            if (match.Success)

            {

                term = match.Groups[1].Value;

            }



            return term.Replace("+", " ");

        }



        /// <summary>

        /// Checks the referrer to see if it qualifies as a search.

        /// </summary>

        /// <returns>

        /// The html string.

        /// </returns>

        private string Html()

        {

            if (this.Context.Request.UrlReferrer != null &&

                !this.Context.Request.UrlReferrer.ToString().Contains(Utils.AbsoluteWebRoot.ToString()) && this.IsSearch)

            {

                var referrer = this.Context.Request.UrlReferrer.ToString().ToLowerInvariant();

                var searchTerm = GetSearchTerm(referrer);

                var items = Search.Hits(searchTerm, false);

                return items.Count == 0 ? null : this.WriteHtml(items, searchTerm);

            }



            return null;

        }



        /// <summary>

        /// Writes the search results as HTML.

        /// </summary>

        /// <param name="items">

        /// The items.

        /// </param>

        /// <param name="searchTerm">

        /// The search Term.

        /// </param>

        /// <returns>

        /// The write html.

        /// </returns>

        private string WriteHtml(IList<IPublishable> items, string searchTerm)

        {

            var results = this.MaxResults < items.Count ? this.MaxResults : items.Count;

            var sb = new StringBuilder();

            sb.Append("<div id=\"searchonsearch\">");

            sb.AppendFormat(

                "<h3>{0} '{1}'</h3>", this.Headline, HttpUtility.HtmlEncode(HttpUtility.UrlDecode(searchTerm)));

            sb.AppendFormat("<p>{0}</p>", this.Text);

            sb.Append("<ol>");



            for (var i = 0; i < results; i++)

            {

                sb.AppendFormat("<li><a href=\"{0}\">{1}</a></li>", items[i].RelativeLink, items[i].Title);

            }



            sb.Append("</ol>");

            sb.Append("</div>");



            return sb.ToString();

        }



        #endregion

    }

}