using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Sitecore.Configuration;
using Sitecore.Data;
using Sitecore.Data.Items;
using Sitecore.Diagnostics;
using Sitecore.Pipelines.HttpRequest;

namespace Sitecore.Support.Pipelines.HttpRequest
{
  public class AliasResolver : HttpRequestProcessor
  {
    public override void Process(HttpRequestArgs args)
    {
      Assert.ArgumentNotNull(args, "args");
      if (!Settings.AliasesActive)
      {
        Tracer.Warning("Aliases are not active.");
        return;
      }
      Database database = Context.Database;
      if (database == null)
      {
        Tracer.Warning("There is no context database in AliasResover.");
        return;
      }

      Profiler.StartOperation("Resolve alias.");
      // Use the Context.Site.Name property to find the site specific aliases
      if (database.Aliases.Exists('/' + Context.Site.Name + args.LocalPath) && !this.ProcessItem(args))
      {
        this.ProcessExternalUrl(args);
      }
      Profiler.EndOperation();
    }

    private void ProcessExternalUrl(HttpRequestArgs args)
    {
      // Use the Context.Site.Name property to find the site specific aliases
      string targetUrl = Context.Database.Aliases.GetTargetUrl('/' + Context.Site.Name + args.LocalPath);
      if (targetUrl.Length > 0)
      {
        this.ProcessExternalUrl(targetUrl);
      }
    }

    private void ProcessExternalUrl(string path)
    {
      if (Context.Page.FilePath.Length > 0)
      {
        return;
      }
      Context.Page.FilePath = path;
    }

    private bool ProcessItem(HttpRequestArgs args)
    {
      // Use the Context.Site.Name property to find the site specific aliases
      ID targetID = Context.Database.Aliases.GetTargetID('/' + Context.Site.Name + args.LocalPath);
      if (!targetID.IsNull)
      {
        Item item = args.GetItem(targetID);
        if (item != null)
        {
          this.ProcessItem(args, item);
        }
        return true;
      }
      // Use the Context.Site.Name property to output porper information
      Tracer.Error("An alias for \"" + "/" + Context.Site.Name + args.LocalPath + "\" exists, but points to a non-existing item.");
      return false;
    }

    private void ProcessItem(HttpRequestArgs args, Item target)
    {
      if (Context.Item == null)
      {
        Context.Item = target;
        // Use the Context.Site.Name property to output proper information
        Tracer.Info(string.Concat(new object[]
				{
					"Using alias for \"",
                    "/",
                    Context.Site.Name,
					args.LocalPath,
					"\" which points to \"",
					target.ID,
					"\""
				}));
      }
    }
  }
}