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Resolve JS Images In Output TBB

Image
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The TBB of this week is Resolve JS Images In Output, originally written by my colleague Eric Huiza. Basically, the TBB does what the name says. It looks for certain images in the Output item and publishes them.

The images have to be in TcmUri or WebDAV format and they must appear in the url('path') format. This is the format that a CSS background selector uses, for example, only that it appears in JavaScript.

The TB transforms something like:

document.getElementById(openingTitleId).style.background=
    "url('/webdav/Content/Building Blocks/Assets/images/titlebar.gif') no-repeat";

into this:

document.getElementById(openingTitleId).style.background=
    "url('/assets/images/titlebar_tcm1-2.gif') no-repeat";

Description

Name
Resolve JS Images In Output TBB
Type
·    Template in .NET Assembly
Description
Used to:
·    Resolve references to Multimedia Components TcmUris or WebDAV URLs inside JS syntax;
·    Publishe the MMC and replaces the TcmUri/WebDAV reference with the resolved URL;
Notes:
This generic TBB uses the Output item to search for references to MMC TcmUris (or WebDav URLs) inside JavaScript references to CSS ‘background’ selectors.
If such MMC TcmUri is identified, the MMC is published (to the mapped Structure Group) and the returned URL replaces the TcmUri reference.
The Output item is rewritten with the resolved URLs.
Parameters
n/a
Applicable to
Any template where an Item called ‘Output’ exists in the Package

Code

[TcmTemplateTitle("Resolve JS Images In Output TBB")]
public class ResolveJsImagesInOutput : ITemplate {

    public const string JS_IMG_REG_EX = @"(url[\s]*\([\s]*(?<url>[^\)]*)[\s]*\))+";
    public readonly Regex cssBgRegEx = new Regex(JS_IMG_REG_EX, RegexOptions.IgnoreCase);

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

        foreach (Match match in GetUrlEntities(js)) {
            string uri = match.Groups["url"].Value.Replace("\"", string.Empty).Replace("'", string.Empty);
            string localUri = utils.LocalizeUri(engine, uri);
            Component imgComponent = engine.GetObject(localUri) as Component;
            if (imgComponent != null) {
                Binary binary = utils.PublishBinary(engine, package, imgComponent);
                js = js.Replace(uri, binary.Url);
            }
        }

        outputItem.SetAsString(js);
    }

    private IEnumerable<Match> GetUrlEntities(string js) {
        return cssBgRegEx.Matches(js).Cast<Match>().
            Where(w => w.Groups["url"].Value.StartsWith("\"/webdav") ||
                w.Groups["url"].Value.StartsWith("'/webdav") ||
                w.Groups["url"].Value.StartsWith("\"tcm:") ||
                w.Groups["url"].Value.StartsWith("'tcm:"));
    }
}

where the util.LocalizeUri method is the following:

public string LocalizeUri(Engine engine, string tcmUri) {
    if (TcmUri.IsValid(tcmUri)) {
        return engine.LocalizeUri(new TcmUri(tcmUri));
    } else {
        return tcmUri;
    }
}


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