Link Attributes Extension: Template Building Block

Earlier we talked about customizing an existing default popup in Tridion, and the post gave birth to the start of our Link Attributes GUI Extension.  As a recap, we were creating an extension that would allow us to add custom link attributes onto our hyperlinks added by the Hyperlink button.  We decided that the GUI Extension would add hash parameters to the link’s href attribute, and that’s pretty much where the post left off.  Today we will be adding a Template Building Block that will be responsible for stripping out the hash parameters that were added by the GUI Extension and converting them to attributes on the link element itself.

In another post we mentioned using HtmlAgilityPack in our Template Building Blocks, so although the regex for this task would be fairly simple, I’ll be using that library in our TBB.  If you are going to be using this extension and this TBB yourself, you’ll have to add the HtmlAgilityPack DLL to the GAC on your Tridion servers as well as reference it in your TBB project.

Next you will want to create a new class in your TBB project and add the following code:

using System;
using System;
using HtmlAgilityPack;
using Tridion.ContentManager.Templating;
using Tridion.ContentManager.Templating.Assembly;

namespace ContentBlooom.TemplateBuildingBlocks
{
    /// <summary>
    /// This TBB is responsible for converting the linkAttr- hash params created by the GUI Extension  into actual
    /// attributes on the link element that they've been placed.
    /// </summary>
    [TcmTemplateTitle("Link Attributes Converter")]
    public class LinkAttributesConverter : ITemplate
    {
        public void Transform(Engine engine, Package package)
        {
            bool outputModified = false;
            Item outputItem = package.GetByName(Package.OutputName);
            string outputString = outputItem.GetAsString();

            HtmlDocument doc = new HtmlDocument();
            doc.LoadHtml(outputString);
            doc.OptionOutputOriginalCase = true;

            var linksWithAttributes = doc.DocumentNode.SelectNodes("//a[contains(@href, 'linkAttr-')]");
            if (linksWithAttributes == null)
            {
                return;
            }
            
            foreach (var link in linksWithAttributes)
            {
                string url = link.Attributes["href"].Value;
                string hashString = url.Substring(url.IndexOf("#") + 1);
                string[] hashParams = hashString.Replace("&amp;", "&").Split('&');
                
                bool hasLinkAttributes = false;

                url = url.Substring(0, url.IndexOf("#"));
                hashString = String.Empty;

                foreach (string hashParam in hashParams)
                {
                    if (hashParam.StartsWith("linkAttr-"))
                    {
                        // If its a link attribute, add it as an attribute and then remove it from the hash string
                        hasLinkAttributes = true;
                        outputModified = true;

                        string[] rule = hashParam.Split('=');
                        string attributeKey = rule[0];
                        string attributeValue = rule[1];

                        link.Attributes.Add(attributeKey.Replace("linkAttr-", String.Empty), attributeValue);
                        url = url.Replace(hashParam, String.Empty);
                    }
                    else
                    {
                        // Keep any existing hash info there...
                        hashString += hashString.Length == 0 ? "#" : "&amp;";
                        hashString += hashParam;
                    }
                }
                if (hasLinkAttributes)
                {
                    link.Attributes["href"].Value = url + hashString;
                }
            }

            if (outputModified)
            {
                package.Remove(outputItem);
                outputItem.SetAsString(doc.DocumentNode.OuterHtml);
                package.PushItem(Package.OutputName, outputItem);
            }
        }
    }
}

Simple, no? You’ll want to put this TBB directly after your Building Block that provides the output (your DWT, Razor… whatever). Or even possibly as the first item in your Default Finish Actions. Make sure to create a component that has some links created with our modified Link popup from the earlier article, and run and execute.

Output prior to Link Attribute Converter:

<article>
    <p>Testing link attributes and what not and other stuff.</p>  
    <p>Should include a <a href="tcm:14-103941#linkAttr-newLink=test" title="a title">component link</a> as well as a normal <a href="http://www.example.com#linkAttr-custom=check" title="blah">http type of link</a>.</p>
    <p>We also need to see how it plays with <a href="http://www.test.com#blah=meh&amp;linkAttr-t=v">links with hashes</a> already.</p>
    <p><a href="mailto:e@mail.com#a=b&amp;c=d&amp;linkAttr-mailed=them" title="title">Multi hashed Link</a></p>
 </article>

And our output after our TBB:

 <article>
     <p>Testing link attributes and what not and other stuff.</p>  
     <p>Should include a <a href="tcm:14-103941" title="a title" newlink="test">component link</a> as well as a normal <a href="http://www.example.com" title="blah" custom="check">http type of link</a>.</p>
     <p>We also need to see how it plays with <a href="http://www.test.com#blah=meh" t="v">links with hashes</a> already.</p>
     <p><a href="mailto:e@mail.com#a=b&amp;c=d" title="title" mailed="them">Multi hashed Link</a></p>
 </article>

Not Quite Done

Our extension is not quite done just yet. Stay tuned once more as we add some enhancements and fixes to our little extension, such as the ability to add more than just one link attribute!