RedirectProcessor.cs

﻿// --------------------------------------------------------------------------------------------------------------------
// <copyright file="Redirects.cs">
//   Copyright (C) 2012 by Alexander Davyduk. All rights reserved.
// </copyright>
// <summary>
//   Redirects class
// </summary>
// --------------------------------------------------------------------------------------------------------------------

using Sitecore.Diagnostics;
using Sitecore.Rules.Conditions;
using Sitecore.Shell.Applications.ContentEditor;
using Sitecore.StringExtensions;
using Sitecore.Web.UI.XamlSharp.Xaml.Extensions;

namespace Sitecore.SharedSource.RedirectManager
{
  using System.Collections;
  using System.Collections.Generic;
  using System.Diagnostics;
  using System.IO;
  using System.Linq;
  using System.Text.RegularExpressions;
  using System.Threading;
  using System.Web;
  using Newtonsoft.Json;
  using Sitecore.Configuration;
  using Data;
  using Data.Fields;
  using Data.Items;
  using Items;
  using Templates;
  using Utils;
  using LayoutField = Data.Fields.LayoutField;

  /// <summary>
  /// Redirects class 
  /// </summary>
  public static class RedirectProcessor
  {
    /// <summary>
    ///   Cache key for items redirects
    /// </summary>
    private const string ItemsCacheKey = "Sitecore.RedirectManager-Items " + ItemIDs.RedirectsFolderItem;

    /// <summary>
    ///   Cache key for sections redirects
    /// </summary>
    private const string SectionsCacheKey = "Sitecore.RedirectManager-Sections " + ItemIDs.RedirectsFolderItem;

    /// <summary>
    ///   Cache key for RegEx redirects
    /// </summary>
    private const string RegExCacheKey = "Sitecore.RedirectManager-RegEx " + ItemIDs.RedirectsFolderItem;

    private const string IndexesPath = "~/temp/";

    /// <summary>
    ///  local variable for synchronization
    /// </summary>
    private static readonly object SyncObject = new object();

    /// <summary>
    /// The multisites
    /// </summary>
    private static Dictionary<ID, string> multisites; 

    /// <summary>
    /// Initializes this instance.
    /// </summary>
    public static void Initialize()
    {
      UrlNormalizer.Initialize();
    }

    /// <summary>
    /// Gets the multisites.
    /// </summary>
    /// <value>
    /// The multisites.
    /// </value>
    public static Dictionary<ID, string> Multisites
    {
      get
      {
        if (multisites == null)
        {
          RebuildMultisites();
        }

        return multisites;
      }
    }

    /// <summary>
    /// Rebuilds the multisites.
    /// </summary>
    public static void RebuildMultisites()
    {
      var sitesFolder = Factory.GetDatabase(Configuration.Database).GetItem(ItemIDs.MultisitesFolderItem);
      if (sitesFolder == null)
      {
        LogManager.WriteError(string.Format("Forlder with multisites \"{0}\" not found", ItemIDs.RedirectsFolderItem));
        return;
      }

      if (multisites != null)
      {
        multisites.Clear();
      }
      else
      {
        multisites = new Dictionary<ID, string>();
      }

      foreach (var site in sitesFolder.Axes.GetDescendants().Where(x => x.TemplateID == Multisite.TemplateId).Select(x => new Multisite(x)).Where(site => !string.IsNullOrEmpty(site.MultisitePrefix.Value)))
      {
        multisites.Add(site.ID, site.MultisitePrefix.Value);
      }
    }

    /// <summary>
    /// Updates the last use in thread.
    /// </summary>
    /// <param name="id">The id.</param>
    public static void UpdateLastUseInThread(string id)
    {
      var newThread = new Thread(UpdateLastUse);
      newThread.Start(id);
    }

    /// <summary>
    /// Creates the list with redirects in thread.
    /// </summary>
    public static void CreateListOfRedirectsInThread()
    {
      var newThread = new Thread(CreateListOfRedirects);
      newThread.Start();
    }

    /// <summary>
    /// Finds the redirect.
    /// </summary>
    /// <param name="url">The requested URL.</param>
    /// <param name="redirectCode">The redirect code.</param>
    /// <param name="redirectId">The redirect id.</param>
    /// <returns>
    /// target url
    /// </returns>
    public static string FindRedirect(string url, out int redirectCode, out string redirectId)
    {
      redirectCode = Configuration.RedirectStatusCode;
      redirectId = string.Empty;

      var targetRedirect = FindItemToItemRedirect(url);
      if (targetRedirect != null)
      {
        /*if (!CheckVirtualFolder(targetRedirect.Multisites, targetRedirect.UseOnDefault))
        {
          LogManager.WriteInfo("Redirect {0} is found, but multisite {1} is not alloved".FormatWith(targetRedirect.ItemId, UrlNormalizer.EncodeUrl(UrlNormalizer.GetVirtualVolder())));
          return string.Empty;
        }*/

        redirectId = targetRedirect.ItemId.ToString();
        redirectCode = targetRedirect.RedirectCode;
        return PrepareRedirectUrl(targetRedirect);
      }

      targetRedirect = FindSectionToItemRedirect(url);
      if (targetRedirect != null)
      {
        /*if (!CheckVirtualFolder(targetRedirect.Multisites, targetRedirect.UseOnDefault))
        {
          LogManager.WriteInfo("Redirect {0} is found, but multisite {1} is not alloved".FormatWith(targetRedirect.ItemId, UrlNormalizer.EncodeUrl(UrlNormalizer.GetVirtualVolder())));
          return string.Empty;
        }*/

        redirectId = targetRedirect.ItemId.ToString();
        redirectCode = targetRedirect.RedirectCode;
        return PrepareRedirectUrl(targetRedirect);
      }

      var encodedUrl = UrlNormalizer.EncodeUrl(string.Format("{0}{1}", UrlNormalizer.GetVirtualVolder(), UrlNormalizer.RemovePageExtension(url)));
      var targetRegExRedirect = FindRegExRedirect(encodedUrl);
      if (targetRegExRedirect != null)
      {
        redirectId = targetRegExRedirect.ItemId.ToString();
        redirectCode = targetRegExRedirect.RedirectCode;
        return PrepareRedirectUrl(targetRegExRedirect, encodedUrl);
      }

      return string.Empty;
    }

    /// <summary>
    /// Gets the redirects.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <returns>List of redirects</returns>
    public static List<RedirectItem> GetRedirects(string cacheKey)
    {
      return HttpRuntime.Cache.Get(cacheKey) as List<RedirectItem>;
    }

    /// <summary>
    /// Gets the regex redirects.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <returns>
    /// The regex redirects.
    /// </returns>
    public static List<RegExItem> GetRegExRedirects(string cacheKey)
    {
      return HttpRuntime.Cache.Get(cacheKey) as List<RegExItem>;
    }

    /// <summary>
    /// Removes the redirect in thread.
    /// </summary>
    /// <param name="item">The item.</param>
    public static void RemoveRedirectInThread(Item item)
    {
      var thread = new Thread(RemoveRedirect);
      thread.Start(item);
    }

    /// <summary>
    /// Removes the redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    private static void RemoveRedirect(object item)
    {
      var itemToRemove = item as Item;
      if (itemToRemove == null)
      {
        return;
      }

      lock (SyncObject)
      {
        var sw = new Stopwatch();
        sw.Start();
        var itemsList = GetRedirects(ItemsCacheKey);
        var sectionsList = GetRedirects(SectionsCacheKey);
        var regExList = GetRegExRedirects(RegExCacheKey);

        CheckItemTypeAndRemove(itemToRemove, itemsList, sectionsList, regExList, out itemsList, out sectionsList, out regExList);

        SaveRedirects(ItemsCacheKey, itemsList);
        SaveRedirects(SectionsCacheKey, sectionsList);
        SaveRedirects(RegExCacheKey, regExList);
        sw.Stop();
        LogManager.WriteInfo(
          string.Format(
            "Redirect for the {0} item was removed: elapsed time - {1} milliseconds",
            itemToRemove.ID,
            sw.ElapsedMilliseconds));
      }
    }

    /// <summary>
    /// Creates the list of redirects.
    /// </summary>
    public static void CreateListOfRedirects()
    {
      CreateListOfRedirects(false);
    }

    /// <summary>
    /// Creates the list of redirects.
    /// </summary>
    /// <param name="readFromIndex">if set to <c>true</c> [read from index].</param>
    private static void CreateListOfRedirects(bool readFromIndex)
    {
      lock (SyncObject)
      {
        var sw = new Stopwatch();
        sw.Start();
        var redirectForlder = Factory.GetDatabase(Configuration.Database).GetItem(ItemIDs.RedirectsFolderItem);
        if (redirectForlder == null)
        {
          LogManager.WriteError(string.Format("Forlder with redirects \"{0}\" not found", ItemIDs.RedirectsFolderItem));
          return;
        }

        var itemsRedirectsList = new List<RedirectItem>();
        var sectionsRedirectList = new List<RedirectItem>();
        var regExRedirectList = new List<RegExItem>();

        if (readFromIndex)
        {
          itemsRedirectsList = GetRedirectsFromIndexFile(ItemsCacheKey);
          sectionsRedirectList = GetRedirectsFromIndexFile(SectionsCacheKey);
          regExRedirectList = GetRegExRedirectsFromIndexFile(RegExCacheKey);
        }

        if (itemsRedirectsList.Count == 0 && sectionsRedirectList.Count == 0 && regExRedirectList.Count == 0)
        {
          ProcessChildren(
            redirectForlder, 
            itemsRedirectsList, 
            sectionsRedirectList, 
            regExRedirectList,
            out itemsRedirectsList,
            out sectionsRedirectList, 
            out regExRedirectList);

          SaveRedirects(ItemsCacheKey, itemsRedirectsList);
          SaveRedirects(SectionsCacheKey, sectionsRedirectList);
          SaveRedirects(RegExCacheKey, regExRedirectList);
        }

        SaveRedirects(ItemsCacheKey, itemsRedirectsList, !readFromIndex);
        SaveRedirects(SectionsCacheKey, sectionsRedirectList, !readFromIndex);
        SaveRedirects(RegExCacheKey, regExRedirectList, !readFromIndex);

        sw.Stop();
        LogManager.WriteInfo(
          string.Format(
            "Lists with redirects were created: total number of redirects - {0}, elapsed time - {1}",
            itemsRedirectsList.Count + sectionsRedirectList.Count + regExRedirectList.Count,
            sw.Elapsed));
      }
    }

    /// <summary>
    /// Processes the children.
    /// </summary>
    /// <param name="rootItem">The root item.</param>
    /// <param name="itemsRedirectsList">The items redirects list.</param>
    /// <param name="sectionsRedirectList">The sections redirect list.</param>
    /// <param name="regExList">The reg ex list.</param>
    /// <param name="itemsRedirectsListOut">The items redirects list out.</param>
    /// <param name="sectionsRedirectListOut">The sections redirect list out.</param>
    /// <param name="regExListOut">The reg ex list out.</param>
    private static void ProcessChildren(Item rootItem,
      List<RedirectItem> itemsRedirectsList,
      List<RedirectItem> sectionsRedirectList,
      List<RegExItem> regExList,
      out List<RedirectItem> itemsRedirectsListOut,
      out List<RedirectItem> sectionsRedirectListOut,
      out List<RegExItem> regExListOut)
    {
      itemsRedirectsListOut = itemsRedirectsList;
      sectionsRedirectListOut = sectionsRedirectList;
      regExListOut = regExList;

      foreach (var item in rootItem.GetChildren().ToArray())
      {
        if (!item.Publishing.IsPublishable(System.DateTime.Now, true))
        {
          continue;
        }

        List<RedirectItem> bufItemsRedirectsList;
        List<RedirectItem> bufSectionsRedirectList;
        List<RegExItem> bufRegExRedirectList;

        CheckRedirectType(item, out bufItemsRedirectsList, out bufSectionsRedirectList, out bufRegExRedirectList);
        if (bufItemsRedirectsList != null)
        {
          itemsRedirectsListOut.AddRange(bufItemsRedirectsList);
        }

        if (bufSectionsRedirectList != null)
        {
          sectionsRedirectListOut.AddRange(bufSectionsRedirectList);
        }

        if (bufRegExRedirectList != null)
        {
          regExListOut.AddRange(bufRegExRedirectList);
        }

        ProcessChildren(item, itemsRedirectsList, sectionsRedirectList, regExList, out itemsRedirectsList, out sectionsRedirectList, out regExList);
      }
    }

    /// <summary>
    /// The check presentation.
    /// </summary>
    /// <param name="item">
    /// The item.
    /// </param>
    /// <returns>
    /// The <see cref="bool"/>.
    /// </returns>
    public static bool CheckPresentation(Item item)
    {
      if (!Configuration.CheckPresentation)
      {
        return true;
      }

      if (item == null)
      {
        return false;
      }

      LayoutField field = item.Fields[FieldIDs.LayoutField];
      return field != null && !string.IsNullOrEmpty(field.Value);
    }

    /// <summary>
    /// Updates the last use.
    /// </summary>
    /// <param name="id">The id.</param>
    private static void UpdateLastUse(object id)
    {
      var itemId = id.ToString();

      var item = Factory.GetDatabase(Configuration.Database).GetItem(itemId);
      if (item == null || !item.IsItemOfType(Templates.Settings.TemplateId))
      {
        return;
      }

      var settingItem = new Templates.Settings(item);
      settingItem.UpdateLastUseWithCurrentDate();
    }

    /// <summary>
    /// Converts the multisites.
    /// </summary>
    /// <param name="multisitesCollection">The multisites collection.</param>
    /// <returns></returns>
    public static string ConvertMultisites(MultilistField multisitesCollection)
    {
      if (Multisites == null || multisitesCollection == null)
      {
        return string.Empty;
      }

      var sites = (from site in multisitesCollection.GetItems()
                   where Multisites.ContainsKey(site.ID)
                   select Multisites[site.ID]).Aggregate(string.Empty, (current, prefix) => string.Format("{0}|{1}", current, prefix));

      return UrlNormalizer.DecodeUrl(sites.TrimStart('|').ToLower());
    }

    /// <summary>
    /// Checks the virtual folder.
    /// </summary>
    /// <param name="sites">The sites.</param>
    /// <param name="useOnDefault">if set to <c>true</c> [use on default].</param>
    /// <param name="virtualFolder">The virtual folder.</param>
    /// <returns>
    /// True is contains; false otherwise
    /// </returns>
    private static bool CheckVirtualFolder(string sites, bool useOnDefault, string virtualFolder)
    {
      if (!Configuration.EnableMultisites)
      {
        return true;
      }

      if (Context.Site != null && Context.Site.Name == "website")
      {
        return useOnDefault;
      }

      return sites.Contains(virtualFolder);
    }

    /// <summary>
    /// Prepares the redirect URL.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>
    /// The redirect URL.
    /// </returns>
    private static string PrepareRedirectUrl(RedirectItem item)
    {
      if (item == null)
      {
        return string.Empty;
      }

      var queryString = item.TargetQueryString;
      var targetUrl = item.Target;

      if (!string.IsNullOrEmpty(queryString))
      {
        targetUrl = !string.IsNullOrEmpty(Context.Request.QueryString.ToString()) ?
          string.Format("{0}?{1}&{2}", targetUrl, queryString, Context.Request.QueryString) :
          string.Format("{0}?{1}", targetUrl, queryString);
      }
      else
      {
        if (!string.IsNullOrEmpty(Context.Request.QueryString.ToString()))
        {
          targetUrl = string.Format("{0}?{1}", targetUrl, Context.Request.QueryString);
        }
      }

      if (!item.External)
      {
        targetUrl = string.Format("{0}{1}", UrlNormalizer.GetVirtualVolder(), targetUrl);
      }

      return UrlNormalizer.EncodeUrl(targetUrl);
    }

    /// <summary>
    /// Prepares the redirect URL.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="url">The URL.</param>
    /// <returns>
    /// The redirect URL.
    /// </returns>
    private static string PrepareRedirectUrl(RegExItem item, string url)
    {
      if (item == null)
      {
        return string.Empty;
      }

      var foundKey = item.Expression.ToString();
      var targetUrl = Regex.Replace(url, foundKey, string.Concat(item.Value, "$2"), RegexOptions.IgnoreCase);

      return UrlNormalizer.EncodeUrl(targetUrl);
    }

    /// <summary>
    /// Checks the item type and remove it.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="itemsList">The items list.</param>
    /// <param name="sectionsList">The sections list.</param>
    /// <param name="regExList">The regex list.</param>
    /// <param name="outputItemsList">The output items list.</param>
    /// <param name="outputSectionsList">The output sections list.</param>
    /// <param name="outputRegExList">The output regex list.</param>
    private static void CheckItemTypeAndRemove(
      Item item,
      List<RedirectItem> itemsList,
      List<RedirectItem> sectionsList,
      List<RegExItem> regExList,
      out List<RedirectItem> outputItemsList,
      out List<RedirectItem> outputSectionsList,
      out List<RegExItem> outputRegExList)
    {
      var templateId = item.TemplateID.ToString();
      switch (templateId)
      {
        case ItemToItem.TemplateId:
          itemsList = RemoveItemToItemRedirect(item, itemsList);
          break;

        case SectionToItem.TemplateId:
          sectionsList = RemoveSectionToItemRedirect(item, sectionsList);
          break;

        case SectionToSection.TemplateId:
          RemoveSectionToSectionRedirect(item, itemsList, sectionsList, out itemsList, out sectionsList);
          break;
        case RegExRedirect.TemplateId:
          regExList = RemoveRegExRedirect(item, regExList);
          break;
      }

      outputItemsList = itemsList;
      outputSectionsList = sectionsList;
      outputRegExList = regExList;
    }

    /// <summary>
    /// Removes the item to item redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="list">The list with items redirects.</param>
    /// <returns>List with removed Item redirect</returns>
    private static List<RedirectItem> RemoveItemToItemRedirect(Item item, List<RedirectItem> list)
    {
      if (list == null)
      {
        return null;
      }

      list.RemoveAll(x => x.ItemId == item.ID);
      return list;
    }

    /// <summary>
    /// Removes the regex redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="list">The list.</param>
    /// <returns>
    /// The regex redirect.
    /// </returns>
    private static List<RegExItem> RemoveRegExRedirect(Item item, List<RegExItem> list)
    {
      if (list == null)
      {
        return null;
      }

      list.RemoveAll(x => x.ItemId == item.ID);
      return list;
    }

    /// <summary>
    /// Removes the section to item redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="list">The list with sections redirects.</param>
    /// <returns>List with removed Section redirect</returns>
    private static List<RedirectItem> RemoveSectionToItemRedirect(Item item, List<RedirectItem> list)
    {
      if (list == null)
      {
        return null;
      }

      list.RemoveAll(x => x.ItemId == item.ID);
      return list;
    }

    /// <summary>
    /// Removes the section to section redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="itemsList">The items list.</param>
    /// <param name="sectionsList">The sections list.</param>
    /// <param name="outItemsList">The out items list.</param>
    /// <param name="outSectionsList">The out sections list.</param>
    private static void RemoveSectionToSectionRedirect(
      Item item,
      List<RedirectItem> itemsList,
      List<RedirectItem> sectionsList,
      out List<RedirectItem> outItemsList,
      out List<RedirectItem> outSectionsList)
    {
      sectionsList = RemoveSectionToItemRedirect(item, sectionsList);
      itemsList = RemoveItemToItemRedirect(item, itemsList);

      outSectionsList = sectionsList;
      outItemsList = itemsList;
    }

    /// <summary>
    /// Checks the redirect type.
    /// </summary>
    /// <param name="item">
    /// The item.
    /// </param>
    /// <param name="itemsRedirectsList">
    /// The items redirects list.
    /// </param>
    /// <param name="sectionsRedirectList">
    /// The sections redirect list.
    /// </param>
    /// <param name="regExList">
    /// The regex redirect list.
    /// </param>
    /// ///
    private static void CheckRedirectType(
      Item item, out List<RedirectItem> itemsRedirectsList, out List<RedirectItem> sectionsRedirectList, out List<RegExItem> regExList)
    {
      itemsRedirectsList = new List<RedirectItem>();
      sectionsRedirectList = new List<RedirectItem>();
      regExList = new List<RegExItem>();

      switch (item.TemplateID.ToString())
      {
        case ItemToItem.TemplateId:
          itemsRedirectsList = AddItemToList(AddItemToItemRedirect(item), itemsRedirectsList);
          break;

        case SectionToItem.TemplateId:
          sectionsRedirectList = AddItemToList(AddSectionToItemRedirect(item), sectionsRedirectList);
          break;

        case SectionToSection.TemplateId:
          itemsRedirectsList = AddItemsToList(AddSectionToSectionDescendants(item), itemsRedirectsList);
          sectionsRedirectList = AddItemToList(AddSectionToSectionRedirect(item), sectionsRedirectList);
          break;

        case RegExRedirect.TemplateId:
          regExList = AddItemToList(AddRegExRedirect(item), regExList);
          break;

        default:
          return;
      }
    }

    /// <summary>
    /// Adds the item to list.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="list">The list.</param>
    /// <returns>
    /// The list with added item.
    /// </returns>
    private static List<RedirectItem> AddItemToList(RedirectItem item, List<RedirectItem> list)
    {
      if (item != null)
      {
        if (!CheckDuplicates(item.Base, list))
        {
          list.Add(item);
        }
      }

      return list;
    }

    /// <summary>
    /// Adds the item to list.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <param name="list">The list.</param>
    /// <returns>
    /// The item to list.
    /// </returns>
    private static List<RegExItem> AddItemToList(RegExItem item, List<RegExItem> list)
    {
      if (item != null)
      {
        if (!CheckDuplicates(item.Expression, list))
        {
          list.Add(item);
        }
      }

      return list;
    }

    /// <summary>
    /// Adds the items to list.
    /// </summary>
    /// <param name="items">The items.</param>
    /// <param name="list">The list.</param>
    /// <returns>
    /// The list with added items.
    /// </returns>
    private static List<RedirectItem> AddItemsToList(IEnumerable<RedirectItem> items, List<RedirectItem> list)
    {
      if (items != null)
      {
        if (Configuration.CheckDuplicates)
        {
          foreach (var sectionItem in items)
          {
            if (!CheckDuplicates(sectionItem.Base, list))
            {
              list.Add(sectionItem);
            }
          }
        }
        else
        {
          list.AddRange(items);
        }
      }

      return list;
    }

    /// <summary>
    /// Adds the item to item redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>Redirect item</returns>
    private static RedirectItem AddItemToItemRedirect(Item item)
    {
      if (item == null)
      {
        return null;
      }

      var itemToItem = new ItemToItem(item);
      if ((string.IsNullOrEmpty(itemToItem.TargetItem.Url) && itemToItem.TargetItem.TargetItem == null)
        || string.IsNullOrEmpty(itemToItem.BaseItem.Value))
      {
        return null;
      }

      var external = true;
      var targetUrl = itemToItem.TargetItem.Url;
      if (itemToItem.TargetItem.IsInternal)
      {
        if (!CheckPresentation(itemToItem.TargetItem.TargetItem))
        {
          return null;
        }

        targetUrl = UrlNormalizer.GetItemUrl(itemToItem.TargetItem.TargetItem);
        external = false;
      }

      var redirectItem = new RedirectItem
      {
        ItemId = itemToItem.ID,
        Target = targetUrl,
        TargetQueryString = itemToItem.TargetItem.QueryString,
        Base = UrlNormalizer.CheckPageExtension(UrlNormalizer.Normalize(itemToItem.BaseItem.Value)),
        External = external,
        RedirectCode = itemToItem.RedirectCode,
        Multisites = ConvertMultisites(itemToItem.Multisites),
        UseOnDefault = itemToItem.UseOnDefault.Checked
      };

      return redirectItem;
    }

    /// <summary>
    /// Adds the section to item redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>Redirect item</returns>
    private static RedirectItem AddSectionToItemRedirect(Item item)
    {
      if (item == null)
      {
        return null;
      }

      var sectionToItem = new SectionToItem(item);
      if (string.IsNullOrEmpty(sectionToItem.BaseSection.Value)
        || (string.IsNullOrEmpty(sectionToItem.TargetItem.Url) && sectionToItem.TargetItem.TargetItem == null))
      {
        return null;
      }

      var external = true;
      var targetUrl = sectionToItem.TargetItem.Url;
      if (sectionToItem.TargetItem.IsInternal)
      {
        if (!CheckPresentation(sectionToItem.TargetItem.TargetItem))
        {
          return null;
        }

        targetUrl = UrlNormalizer.GetItemUrl(sectionToItem.TargetItem.TargetItem);
        external = false;
      }

      var redirectItem = new RedirectItem
      {
        ItemId = sectionToItem.ID,
        Target = targetUrl,
        TargetQueryString = sectionToItem.TargetItem.QueryString,
        Base = UrlNormalizer.RemovePageExtension(UrlNormalizer.Normalize(sectionToItem.BaseSection.Value)),
        External = external,
        RedirectCode = sectionToItem.RedirectCode,
        Multisites = ConvertMultisites(sectionToItem.Multisites),
        UseOnDefault = sectionToItem.UseOnDefault.Checked
      };

      return redirectItem;
    }

    /// <summary>
    /// Adds the section to section redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>Redirect item</returns>
    private static RedirectItem AddSectionToSectionRedirect(Item item)
    {
      if (item == null)
      {
        return null;
      }

      var sectionToSection = new SectionToSection(item);
      if (string.IsNullOrEmpty(sectionToSection.BaseSection.Value) || sectionToSection.TargetSection.TargetItem == null)
      {
        return null;
      }

      if (!CheckPresentation(sectionToSection.TargetSection.TargetItem))
      {
        return null;
      }

      var redirectItem = new RedirectItem
      {
        ItemId = sectionToSection.ID,
        Target = UrlNormalizer.GetItemUrl(sectionToSection.TargetSection.TargetItem),
        Base = UrlNormalizer.Normalize(sectionToSection.BaseSection.Value),
        RedirectCode = sectionToSection.RedirectCode,
        Multisites = ConvertMultisites(sectionToSection.Multisites),
        UseOnDefault = sectionToSection.UseOnDefault.Checked
      };

      return redirectItem;
    }

    /// <summary>
    /// Adds the section to section items.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>List with items redirects</returns>
    private static IEnumerable<RedirectItem> AddSectionToSectionDescendants(Item item)
    {
      if (item == null)
      {
        return null;
      }

      var sectionToSection = new SectionToSection(item);
      if (string.IsNullOrEmpty(sectionToSection.BaseSection.Value) || sectionToSection.TargetSection.TargetItem == null)
      {
        return null;
      }

      var list = AddSectionDescendants(
        sectionToSection.TargetSection.TargetItem.ID.ToString(),
        sectionToSection.BaseSection.Value,
        UrlNormalizer.GetItemUrl(sectionToSection.TargetSection.TargetItem),
        sectionToSection.ID,
        sectionToSection.RedirectCode,
        ConvertMultisites(sectionToSection.Multisites),
        sectionToSection.UseOnDefault.Checked);

      return list;
    }

    /// <summary>
    /// Adds the regex redirect.
    /// </summary>
    /// <param name="item">The item.</param>
    /// <returns>redirect item</returns>
    private static RegExItem AddRegExRedirect(Item item)
    {
      if (item == null)
      {
        return null;
      }

      var regExRedirect = new RegExRedirect(item);
      if (string.IsNullOrEmpty(regExRedirect.Expression.Value) || string.IsNullOrEmpty(regExRedirect.Value.Value))
      {
        return null;
      }

      var redirectItem = new RegExItem
      {
        ItemId = regExRedirect.ID,
        Value = new Regex(regExRedirect.Value.Value, RegexOptions.IgnoreCase),
        Expression = new Regex(regExRedirect.Expression.Value, RegexOptions.IgnoreCase),
        RedirectCode = regExRedirect.RedirectCode
      };

      return redirectItem;
    }

    /// <summary>
    /// Finds the item to item redirect.
    /// </summary>
    /// <param name="url">The URL.</param>
    /// <returns>Item target url</returns>
    private static RedirectItem FindItemToItemRedirect(string url)
    {
      var list = GetRedirects(ItemsCacheKey);

      if (list == null)
      {
        return null;
      }

      var found = list.AsParallel().Where(x => x.Base == url);
      if (!found.Any())
      {
        return null;
      }

      var virtualFolder = UrlNormalizer.GetVirtualVolder().TrimStart('/');
      var target =
        found.FirstOrDefault(
          x => CheckVirtualFolder(x.Multisites, x.UseOnDefault, virtualFolder));

      if (target == null)
      {
        LogManager.WriteInfo("Found {0} redirect(s) - {1} for {2} url, but neither is allowed for {3} site".FormatWith(found.Count(), Enumerable.Aggregate(found, string.Empty, (current, item) => current + "|" + item.ItemId).TrimStart('|'), url, virtualFolder));
      }


      return target;
    }

    /// <summary>
    /// Finds the section to item.
    /// </summary>
    /// <param name="url">The URL.</param>
    /// <returns>section target url</returns>
    private static RedirectItem FindSectionToItemRedirect(string url)
    {
      var list = GetRedirects(SectionsCacheKey);

      if (list == null)
      {
        return null;
      }

      var found = list.AsParallel().Where(x => url.StartsWith(x.Base));
      if (!found.Any())
      {
        return null;
      }

      var virtualFolder = UrlNormalizer.GetVirtualVolder().TrimStart('/');
      var target =
        found.AsParallel()
          .FirstOrDefault(
            x => CheckVirtualFolder(x.Multisites, x.UseOnDefault, virtualFolder));

      if (target == null)
      {
        LogManager.WriteInfo("Found {0} redirects - {1} for {2} url, but neither is allowed for {3} site".FormatWith(found.Count(), Enumerable.Aggregate(found, string.Empty, (current, item) => current + "|" + item.ItemId).TrimStart('|'), url, virtualFolder));
      }

      return target;
    }

    /// <summary>
    /// Finds the regex redirect.
    /// </summary>
    /// <param name="url">The URL.</param>
    /// <returns>
    /// The regex redirect.
    /// </returns>
    private static RegExItem FindRegExRedirect(string url)
    {
      var list = GetRegExRedirects(RegExCacheKey);

      if (list == null)
      {
        return null;
      }

      return list.AsParallel().FirstOrDefault(x => x.Expression.IsMatch(url));
    }

    /// <summary>
    /// Adds the section descendants.
    /// </summary>
    /// <param name="targetItemId">The target item id.</param>
    /// <param name="baseSectionUrl">The base section URL.</param>
    /// <param name="targetSectionUrl">The target section URL.</param>
    /// <param name="itemId">The item id.</param>
    /// <param name="redirectCode">The redirect code.</param>
    /// <param name="multisites">The multisites.</param>
    /// <param name="useOnDefaultSite">if set to <c>true</c> [use on default site].</param>
    /// <returns>
    /// list of items redirects
    /// </returns>
    private static IEnumerable<RedirectItem> AddSectionDescendants(
      string targetItemId, string baseSectionUrl, string targetSectionUrl, ID itemId, int redirectCode, string multisites, bool useOnDefaultSite)
    {
      var sectionItem = Factory.GetDatabase(Configuration.Database).GetItem(targetItemId);

      if (sectionItem == null)
      {
        return null;
      }

      var list = new List<RedirectItem>();

      if (CheckPresentation(sectionItem))
      {
        var sectionRedirectItem = new RedirectItem
        {
          ItemId = itemId,
          Target = targetSectionUrl,
          Base = UrlNormalizer.CheckPageExtension(baseSectionUrl),
          RedirectCode = redirectCode,
          Multisites = multisites,
          UseOnDefault = useOnDefaultSite
        };

        list.Add(sectionRedirectItem);
      }

      baseSectionUrl = UrlNormalizer.Normalize(baseSectionUrl);
      targetSectionUrl = UrlNormalizer.RemovePageExtension(targetSectionUrl);

      if (targetSectionUrl == "/")
      {
        list.AddRange(
          from item in sectionItem.Axes.GetDescendants().Where(CheckPresentation)
          select UrlNormalizer.GetItemUrl(item)
            into targetUrl
            let baseUrl = string.Format("{0}{1}", baseSectionUrl, targetUrl)
            select new RedirectItem
            {
              ItemId = itemId,
              Target = targetUrl,
              Base = baseUrl,
              External = false,
              RedirectCode = redirectCode,
              Multisites = multisites,
              UseOnDefault = useOnDefaultSite
            });
      }
      else
      {
        list.AddRange(
         from item in sectionItem.Axes.GetDescendants().Where(CheckPresentation)
         select UrlNormalizer.GetItemUrl(item)
           into targetUrl
           let baseUrl = targetUrl.Replace(targetSectionUrl, baseSectionUrl)
           select new RedirectItem
           {
             ItemId = itemId,
             Target = targetUrl,
             Base = baseUrl,
             External = false,
             RedirectCode = redirectCode,
             Multisites = multisites,
             UseOnDefault = useOnDefaultSite
           });
      }

      return list;
    }

    /// <summary>
    /// Saves the redirects.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <param name="redirectsList">The redirects list.</param>
    /// <param name="saveToIndex">if set to <c>true</c> [save to index].</param>
    private static void SaveRedirects(string cacheKey, ICollection redirectsList, bool saveToIndex = true)
    {
      HttpRuntime.Cache.Remove(cacheKey);
      HttpRuntime.Cache.Insert(cacheKey, redirectsList);
      if (saveToIndex)
      {
        SaveRedirectsToIndexFile(cacheKey, redirectsList);
      }
    }

    /// <summary>
    /// Saves to index file.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <param name="redirectsList">The redirects list.</param>
    private static void SaveRedirectsToIndexFile(string cacheKey, ICollection redirectsList)
    {
      lock (SyncObject)
      {
        var filePath =
          System.Web.Hosting.HostingEnvironment.MapPath(string.Format("{0}{1}.index", IndexesPath, cacheKey));

        if (filePath == null)
        {
          return;
        }

        if (File.Exists(filePath))
        {
          File.Delete(filePath);
        }

        var indexBody = JsonConvert.SerializeObject(redirectsList);
        File.WriteAllText(filePath, indexBody);
      }
    }

    /// <summary>
    /// Gets the index from file.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <returns>redirects list</returns>
    private static List<RedirectItem> GetRedirectsFromIndexFile(string cacheKey)
    {
      lock (SyncObject)
      {
        var filePath = HttpContext.Current.Request.MapPath(string.Format("{0}{1}.index", IndexesPath, cacheKey));

        if (!File.Exists(filePath))
        {
          return new List<RedirectItem>();
        }

        var body = File.ReadAllText(filePath);
        return !string.IsNullOrEmpty(body)
                 ? JsonConvert.DeserializeObject<List<RedirectItem>>(body)
                 : new List<RedirectItem>();
      }
    }

    /// <summary>
    /// Gets the reg ex redirects from index file.
    /// </summary>
    /// <param name="cacheKey">The cache key.</param>
    /// <returns>list with RegExItem redirects</returns>
    private static List<RegExItem> GetRegExRedirectsFromIndexFile(string cacheKey)
    {
      var filePath = HttpContext.Current.Request.MapPath(string.Format("{0}{1}.index", IndexesPath, cacheKey));

      if (!File.Exists(filePath))
      {
        return new List<RegExItem>();
      }

      var body = File.ReadAllText(filePath);
      return !string.IsNullOrEmpty(body) ? JsonConvert.DeserializeObject<List<RegExItem>>(body) : new List<RegExItem>();
    }

    /// <summary>
    /// Checks the duplicates.
    /// </summary>
    /// <param name="url">The URL.</param>
    /// <param name="redirectsList">The redirects list.</param>
    /// <returns>true if there are a duplicates, false otherwise</returns>
    private static bool CheckDuplicates(string url, IEnumerable<RedirectItem> redirectsList)
    {
      if (Configuration.CheckDuplicates)
      {
        if (redirectsList != null)
        {
          var found = redirectsList.AsParallel().Where(x => x.Base == url);
          var firstOrDefault = found.FirstOrDefault();
          if (firstOrDefault != null)
          {
            return true;
          }
        }
      }

      return false;
    }

    /// <summary>
    /// Checks the duplicates.
    /// </summary>
    /// <param name="expression">The expression.</param>
    /// <param name="redirectsList">The redirects list.</param>
    /// <returns>
    /// The duplicates.
    /// </returns>
    private static bool CheckDuplicates(Regex expression, IEnumerable<RegExItem> redirectsList)
    {
      if (Configuration.CheckDuplicates)
      {
        if (redirectsList != null)
        {
          var found = redirectsList.AsParallel().Where(x => x.Expression == expression);
          var firstOrDefault = found.FirstOrDefault();
          if (firstOrDefault != null)
          {
            return true;
          }
        }
      }

      return false;
    }
  }
}