Text::TOC – Reality Versus Theory

I released the first version of Text::TOC, so now we can revisit my earlier design in light of an actual implementation.

From a high level, what’s released is pretty similar to what I thought I would release. Here’s what I said the high level process looked like:

  • Process one or more documents for “interesting” nodes.
  • Assemble all the nodes into a table of contents.
  • Annotate the source documents with anchors as needed.
  • Produce a complete table of contents in the specified output format.

This is more or less exactly what the released code does. However, I was also wrong in some cases. I said that “adding anchors and generating a table of contents will also be roles”. In fact, this became one role, Text::TOC::Role::OutputHandler.

The output handler is responsible for iterating over the nodes that were deemed interesting. It adds anchors to the source document via the nodes themselves, which are assumed to somehow connect back to the source document. In the HTML case, I’m using HTML::DOM, so given any node in the document, I can alter the source document in place. At the same time, as it iterates over the nodes, the output handler generates a table of contents.

I still might go back and split these responsibilities up, but for now I wanted to get something released rather than futzing around to find the perfect architecture. Even if I do split them up, the OutputHandler abstraction is useful. In the future an OutputHandler could just delegate to an AnchorInserter and TOCBuilder.

I got some other parts right too. I said …

Different types of source documents will produce different types of nodes. For an HTML document, the node contents will probably be a DOM fragment representing the content of a given tag.

That is exactly how the released code works.

I also said that finding “interesting” nodes would be a role. It is, and in the HTML implementation there are sane defaults for single- and multi-document tables of contents.

I planned to have an API for managing the formatting of the TOC, but I punted on that for now. Your current choices are unordered or ordered lists. This is good enough for my needs, and therefore good enough for a first release.

Finally, the shortcut API I proposed was a bit off. I eventually realized that the key decision is whether we’re making a single- versus multi-document table of contents. That decision determines what is the sane default for a node filter, and a sane link generation strategy. In the multi-doc case you’ll always have to provide your own link generator, since I can’t know your URI space.

I also punted entirely on embedding the table of contents in the output document. You can do that yourself for now. The code is on CPAN or in my mercurial repo, so feel free to take a closer look. I hope this will be of use to others as well. I don’t know if there will ever be interest in working with non-HTML documents, but even as it is I think it’s more useful than the other HTML TOC tools that previously existed on CPAN.

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