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+permalink: "/{{ year }}/{{ month }}/{{ day }}/mdbook-toc-and-mermaid-preprocessors"
+title: "mdbook - ToC and Mermaid preprocessors"
+published_date: "2019-07-11 13:40:00 +0200"
+layout: post.liquid
+data:
+ route: blog
+---
+
+[mdbook][] is a tool to create (online) books from markdown files.
+It was created with Rust and is heavily used in the Rust community. Unsurprisingly the biggest and first user is [The Rust Programming Language Book](https://doc.rust-lang.org/book/).
+
+`mdbook` comes with most features you expect from it. It renders directly to HTML,
+but also has alternative backends allowing it to [create ePub files][epub] or do some [link checks on the content][linkcheck].
+
+However it lacks some more extensive features, which we required for some internal documentation.
+So a while back I sat down and added this functionality.
+Back then the only way to extend mdbook's rendering process with more elaborate features was by completely wrapping the mdbook code and add additional features.
+`mdbook` was merely a dependency of whatever additional preprocessor was built.
+This had multiple drawbacks:
+
+* Build multiple preprocessors into one tool or have one tool wrap other preprocessors
+* You need to update the preprocessor's dependencies to get a new mdbook
+* You need to use Rust to write the preprocessor
+
+As long as I controlled both the only usage and the code that was ok for our internal use,
+but the `mdbook` maintainers realised that this is not viable in the long run for them, so they build a new way to use external tools as preprocessors.
+This change should make it much easier to build and use multiple preprocessors.
+I even got a PR to update one of my tools.
+
+I just never got around to merge and release that and then do the same for the other tool.
+Until earlier this week a colleague asked me about the status of that tool, as he had similar requirements for their documentation.
+So during work hours and yesterday's Rust Hack'n'Learn I sat down and integrated the missing pieces to release 2 mdbook preprocessors for easy reuse by others.
+
+
+## mdbook-toc - add inline Table of Contents support
+
+`mdbook-toc` allows you to automatically create Table of Contents per chapter.
+This becomes very useful when you got some long chapters with a lot of little subparts (and you don't want to split it up across chapters/pages).
+
+It turns this markdown:
+
+```markdown
+
+
+# Header 1
+
+## Header 1.1
+```
+
+into this:
+
+```markdown
+* [Header 1](#header-1)
+ * [Header 1.1](#header-11)
+
+# Header 1
+
+## Header 1.1
+```
+
+which eventually becomes:
+
+```html
+
+
+
+
+
+```
+
+## mdbook-mermaid - add mermaid.js support
+
+`mdbook-mermaid` adds [mermaid.js][] support to your book.
+Diagrams and flowcharts are a wonderful thing to explain architecture & data in a much more concise and precise way than text would do.
+Mermaid makes it possible to describe these diagrams in ASCII text, making them easy to modify and track changes over time.
+
+It turns this:
+
+~~~
+```mermaid
+graph TD;
+ A-->B;
+ A-->C;
+ B-->D;
+ C-->D;
+```
+~~~
+
+into this:
+
+
+
+
+## How to use
+
+Usage is rather simple. First you need to install it:
+
+```
+cargo install mdbook-toc mdbook-mermaid
+```
+
+You can also use readily available binaries from the release pages:
+
+* [mdbook-toc release](https://github.com/badboy/mdbook-toc/releases)
+* [mdbook-mermaid releases](https://github.com/badboy/mdbook-mermaid/releases)
+
+You then need a little bit of configuration in your book's `book.toml` (the configuration file).
+
+For `mdbook-toc` this is as simple as:
+
+```toml
+[preprocessor.toc]
+command = "mdbook-toc"
+```
+
+For `mdbook-mermaid` this is slightly more involved:
+
+```toml
+[preprocessor.mermaid]
+command = "mdbook-mermaid"
+renderer = ["html"]
+
+[output.html]
+additional-css = ["mermaid.css"]
+additional-js = ["mermaid.min.js", "mermaid-init.js"]
+```
+
+Copy the files (`mermaid.css`, `mermaid.min.js`, `mermaid-init.js`) from the [`assets/`](https://github.com/badboy/mdbook-mermaid/tree/master/assets) directory in the repository into your source directory.
+
+Once everything is installed & configured, you can build your book as usual:
+
+```
+mdbook build path/to/your/book
+```
+
+And that's it!
+
+## Who uses it?
+
+* [Firefox Data Documentation](https://docs.telemetry.mozilla.org/introduction.html).
+ * I switched the Firefox Data Documentation to `mdbook` a while ago, because the previous tool (`gitbook`) was slow and not maintained anymore.
+ Relying on tooling that's used by the Rust project seemed to be a good bet.
+* [Documentation for Mozilla localizers](https://mozilla-l10n.github.io/localizer-documentation/index.html)
+ * Flod, one of the maintainers of the Localizer Documentation, poked me to ask about `mdbook-toc` earlier this week, because it was outdated and awkward to use.
+ So I went ahead and polished it ready for a release again.
+ It was [quickly integrated](https://github.com/mozilla-l10n/localizer-documentation/pull/157).
+
+[mdbook]: https://github.com/rust-lang-nursery/mdBook
+[epub]: https://github.com/Michael-F-Bryan/mdbook-epub
+[linkcheck]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
+[mdbook-toc]: https://github.com/badboy/mdbook-toc
+[mdbook-mermaid]: https://github.com/badboy/mdbook-mermaid
+[mermaid.js]: https://mermaidjs.github.io/