Generate Leanpub TOC from Asciidoc files

Posted at — Oct 9, 2020

I just released the first version of my Taming Thymeleaf book on leanpub. Since I am using Asciidoctor to generate the PDF, there is no automatic table of contents generation for the landing page. Luckily, leanpub allows to enter some HTML to manually create the TOC.

A perfect opportunity to use my rusty Groovy skills once more to generate this HTML.

I have my Asciidoc files all in a _chapters directory grouped per chapter:

chapter-01.adoc
chapter-02.adoc
chapter-03.adoc
chapter-04.adoc
chapter-05.adoc
...

Asciidoc uses == and === indicate chapter titles. This is an example from chapter-01.adoc:

== What are Spring Boot and Thymeleaf?

=== Spring Framework

Spring Boot is based upon the https://projects.spring.io/spring-framework/[Spring Framework], which is at its core
a dependency-injection container. Spring makes it easy to define everything in your application as loosely coupled
components which Spring will tie together at run time. Spring also has a programming model that allows you to make
abstractions from specific deployment environments.

This Groovy script loops over all files and searches for the level 1 (==) and level 2 (===) Asciidoc headings:

println('<ul class="toc no-parts">')
int chapterNumber = 1;
def files = new File('_chapters').listFiles(new FilenameFilter() {
    @Override
    boolean accept(File dir, String name) {
        return name.startsWith('chapter-')
    }
})
files.sort().each { File file ->
    def lines = file.readLines()
    println('<li>')
    int sectionNumber = 1;
    lines.forEach({ it ->
        if (it.startsWith("== ")) {
            println("<span class=\"section-number\">${chapterNumber++}. </span>${it - "== "}")
            println('<ul>')
        }
        if (it.startsWith("=== ")) {
            println("""
<li>
                <span class="section-number">${chapterNumber}.${sectionNumber++} </span>${it - "=== "}
            </li>
""")
        }
    }
    )
    println('</ul>')
    println('</li>')
}
println('</ul>')

The resulting HTML is something like:

<ul class="toc no-parts">
    <li>
        <span class="section-number">1. </span>What are Spring Boot and Thymeleaf?
        <ul>
            <li>
                <span class="section-number">2.1 </span>Spring Framework
            </li>
            <li>
                <span class="section-number">2.2 </span>Spring Boot
            </li>
            <li>
                <span class="section-number">2.3 </span>Thymeleaf
            </li>
        </ul>
    </li>
    <li>
        <span class="section-number">2. </span>Getting started
        <ul>
            <li>
                <span class="section-number">3.1 </span>Prerequisites
            </li>
            <li>
                <span class="section-number">3.2 </span>Spring Initializer
            </li>
            <li>
                <span class="section-number">3.3 </span>Summary
            </li>
        </ul>
    </li>
    ...
</ul>

See https://leanpub.com/taming-thymeleaf for the full generated Table of Contents.

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Wim Deblauwe

Wim Deblauwe

Generate Leanpub TOC from Asciidoc files