63 lines
2.6 KiB
Markdown
63 lines
2.6 KiB
Markdown
# Mermaid + Marp Pipeline Design
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**Date:** 2026-05-10
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**Status:** Approved
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## Goal
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Enable Mermaid diagrams in Marp presentations without any per-file manual steps for authors. A push to the repo triggers the existing webhook CI, which builds the slides and serves them at `slides.makerfloss.eu`.
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## Context
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- Webhook CI is live: `push → build-slides.sh → slides/` served at `slides.makerfloss.eu`
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- `build-slides.sh` already passes `--html` to marp (raw HTML in markdown is allowed)
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- Marp emits fenced mermaid blocks as `<pre><code class="language-mermaid">…</code></pre>`
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- A previous attempt (`2459b4c`) used a custom `marp.config.mjs` but failed: it overrode `rules.code` instead of `rules.fence`, so mermaid blocks were never transformed. That approach also required `npm install` on the server. It was reverted.
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## Approach: HTML post-processing in `build-slides.sh`
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After the marp build, loop over every `slides/*.html`. For each file that contains `class="language-mermaid"`, inject the following snippet before `</body>`:
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```html
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<script type="module">
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import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
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document.querySelectorAll('code.language-mermaid').forEach(el => {
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const div = document.createElement('div');
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div.className = 'mermaid';
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div.textContent = el.textContent;
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el.closest('pre').replaceWith(div);
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});
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mermaid.initialize({ startOnLoad: false, theme: 'dark' });
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await mermaid.run();
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</script>
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```
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Injection uses `python3` (reliable string replacement, avoids `sed` quoting issues; python3 is available on any Debian-based host).
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### Why this approach
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- Zero server changes required
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- Zero per-file authoring requirements — authors write normal ` ```mermaid ` fences
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- Works with all three build paths in `build-slides.sh` (npx / global marp / Docker)
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- Only injects into files that actually contain mermaid blocks
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### Constraints
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- Mermaid theme hardcoded to `'dark'` — all current presentations use the dark gaia theme
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- Requires browser with ES module support (all modern browsers qualify)
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- Mermaid rendering is client-side; diagrams will not appear in PDF exports
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## Changes
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| File | Change |
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|------|--------|
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| `build-slides.sh` | Add post-processing loop after marp build |
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| `docs/test-mermaid.md` | New test presentation with mermaid diagram |
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## Test plan
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1. Push `docs/test-mermaid.md` to `main`
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2. Webhook triggers; wait for build
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3. Verify `slides.makerfloss.eu/test-mermaid.html` is listed on the index
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4. Open the slide and confirm the mermaid diagram renders (not a code block)
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5. Verify existing slides (`messaging-presentation`, `SoMe-taxonomi`, `labdesign`) are unaffected
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