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Enforce Anchor Target TBB

This week's TBB is Enforce Anchor Target TBB. The functionality is to enforce a 'system-wide' anchor target policy. Namely, any fully qualified URLs should open in a new (_blank) target browser window. All other (relative) URLs should open in the same target. More specifically, if there is a target specified for a relative URL, remove it.

Name
Enforce Anchor Target TBB
Type
·    Template in .NET Assembly
Description
Used to:
·    Enforces a certain “target” attribute for the anchor tags depending on their “href” attribute value;
Notes:
This generic TBB expects an Item called “Output” in the Package.
It parses the Output looking for anchor <a> tags. If the anchor’s “href” attribute is a fully qualified URL (starts with “http://” or “https://”), then it adds/replaces “target” attribute with value “_blank”. Otherwise, it removes the “target” attribute, if present.
Finally the transformed Output is saved back into the Package.
Parameters
n/a
Applicable to
Any template where an Item called ‘Output’ exists in the Package

The Code

[TcmTemplateTitle("Enforce Anchor Target TBB")]
public class EnforceAnchorTarget : ITemplate {

    private const string ANCHOR_REG_EXP = "<a[^>]*>";
    private readonly Regex imgRegExp = new Regex(ANCHOR_REG_EXP, RegexOptions.IgnoreCase);
    private readonly TemplatingLogger log = TemplatingLogger.GetLogger(typeof(EnforceAnchorTarget));

    public void Transform(Engine engine, Package package) {
        GenericUtils utils = new GenericUtils();
        Item outputItem = package.GetByName(Package.OutputName);
        string xhtml = outputItem.GetAsString();

        foreach (Match match in GetAnchorTags(xhtml)) {
            string anchorHtmlTag = match.Value;
            string anchorHref = utils.GetHtmlTagAttributeValue("href", anchorHtmlTag);
            if (anchorHref == null) // anchor without an href
            {
                continue;
            }

            string target = anchorHref.ToLower();
            if (target.StartsWith("http://") || target.StartsWith("https://")) {
                utils.SetHtmlTagAttribute("target", "_blank", ref anchorHtmlTag);
            } else {
                utils.RemoveHtmlTagAttribute("target", ref anchorHtmlTag);
            }

            xhtml = xhtml.Replace(match.Value, anchorHtmlTag);
        }

        outputItem.SetAsString(xhtml);
    }

    private MatchCollection GetAnchorTags(string xhtml) {
        return imgRegExp.Matches(xhtml);
    }
}


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