199 lines
9.2 KiB
Dart
199 lines
9.2 KiB
Dart
import 'dart:convert';
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import 'dart:typed_data';
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import 'package:flutter/services.dart' show rootBundle;
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import '../models/settings.dart';
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/// Builds a single, self-contained HTML file from a deck's Marp Markdown.
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///
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/// The output embeds (inlines) `marked` for Markdown, `highlight.js` for code,
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/// `MathJax` (tex-svg, so no external font files are needed) for math, and
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/// `mermaid` for diagrams — so the resulting `.html` renders fully offline.
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///
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/// Note: this is a Marp-*flavoured* deck rendered with `marked`, not Marp Core,
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/// so theme fidelity differs from the in-app preview / PDF / PPTX. The strength
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/// here is a portable, dependency-free presentation that opens in any browser.
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class MarpHtmlService {
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/// Reads a bundled text asset (defaults to the Flutter asset bundle).
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/// Injectable so the builder can be unit-tested against the on-disk files.
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final Future<String> Function(String asset) loadAsset;
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/// Reads a bundled binary asset (used to embed the EB Garamond font).
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final Future<Uint8List> Function(String asset) loadBytes;
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MarpHtmlService({
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Future<String> Function(String asset)? loadAsset,
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Future<Uint8List> Function(String asset)? loadBytes,
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}) : loadAsset = loadAsset ?? rootBundle.loadString,
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loadBytes =
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loadBytes ??
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((a) async => (await rootBundle.load(a)).buffer.asUint8List());
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static const _assetDir = 'assets/web_export';
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/// Builds the HTML. When [theme] is given, the slides take that profile's
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/// colours and font so the export matches the in-app / PDF look.
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Future<String> build(String deckMarkdown, {ThemeProfile? theme}) async {
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final marked = await loadAsset('$_assetDir/marked.min.js');
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final hljs = await loadAsset('$_assetDir/highlight.min.js');
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final hljsCss = await loadAsset('$_assetDir/highlight.css');
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final mathjax = await loadAsset('$_assetDir/tex-svg.js');
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final mermaid = await loadAsset('$_assetDir/mermaid.min.js');
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final css = theme == null ? _baseCss : await _themedCss(theme);
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final sections = StringBuffer();
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for (final slide in marpSlides(deckMarkdown)) {
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sections
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..write('<section class="slide"><script type="text/markdown">')
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..write(_guard(slide))
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..write('</script></section>');
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}
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String inline(String code) => '<script>${_guard(code)}</script>';
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return '<!doctype html>\n'
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'<html lang="nl"><head><meta charset="utf-8">'
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'<meta name="viewport" content="width=device-width, initial-scale=1">'
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'<title>OciDeck export</title>'
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'<style>$css\n$hljsCss</style>'
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'<script>$_mathjaxConfig</script>'
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'${inline(marked)}'
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'${inline(hljs)}'
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'${inline(mathjax)}'
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'${inline(mermaid)}'
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'</head><body>'
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'$sections'
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'${inline(_renderScript)}'
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'</body></html>';
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}
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/// Split Marp Markdown into per-slide Markdown chunks: drop the leading YAML
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/// front-matter, then break on lines that contain only `---`.
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static List<String> marpSlides(String markdown) {
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var text = markdown.replaceAll('\r\n', '\n');
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// Strip a leading YAML front-matter block: ---\n ... \n---\n
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if (text.startsWith('---\n')) {
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final close = text.indexOf('\n---', 4);
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if (close != -1) {
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final nl = text.indexOf('\n', close + 1);
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text = nl == -1 ? '' : text.substring(nl + 1);
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}
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}
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final slides = <String>[];
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final buf = StringBuffer();
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for (final line in text.split('\n')) {
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if (line.trim() == '---') {
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slides.add(buf.toString().trim());
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buf.clear();
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} else {
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buf.writeln(line);
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}
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}
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slides.add(buf.toString().trim());
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return slides.where((s) => s.isNotEmpty).toList();
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}
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/// Neutralise any `</script` inside inlined content so it can't break out of
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/// the surrounding <script> element. Safe for both JS (string contexts) and
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/// the embedded Markdown payloads.
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static String _guard(String s) => s
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.replaceAll('</script', r'<\/script')
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.replaceAll('</SCRIPT', r'<\/SCRIPT');
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/// CSS that mirrors the deck's [ThemeProfile]: slide background, text and
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/// accent colours, table colours and font. The EB Garamond font is embedded
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/// (base64) so it renders offline; other fonts resolve to system families.
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Future<String> _themedCss(ThemeProfile t) async {
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final fontFace = await _ebGaramondFontFace(t.fontFamily);
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final family = _cssFontStack(t.fontFamily);
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return '$fontFace\n'
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'*{box-sizing:border-box}'
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'html,body{margin:0;padding:0}'
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'body{background:#1e1e1e;font-family:$family;color:${t.textColor}}'
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'.slide{position:relative;width:1280px;min-height:720px;margin:24px auto;'
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'background:${t.slideBackgroundColor};color:${t.textColor};padding:60px;'
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'overflow:hidden;box-shadow:0 4px 24px rgba(0,0,0,.4);border-radius:4px;'
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'font-family:$family}'
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'.slide h1{font-size:48px;margin:.15em 0;color:${t.textColor}}'
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'.slide h2{font-size:34px;margin:.15em 0;color:${t.accentColor}}'
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'.slide a{color:${t.accentColor}}'
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'.slide p,.slide li{font-size:24px;line-height:1.45}'
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'.slide pre{background:#f6f8fa;border:1px solid #e1e4e8;border-radius:6px;'
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'padding:16px;overflow:auto;font-size:18px}'
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'.slide code{font-family:SFMono-Regular,Consolas,"Liberation Mono",monospace}'
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'.slide pre.mermaid{background:transparent;border:0;text-align:center}'
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'.slide img{max-width:100%}'
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'.slide blockquote{border-left:4px solid ${t.accentColor};margin:.5em 0;'
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'padding-left:16px;opacity:.85}'
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'.slide table{border-collapse:collapse}'
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'.slide th{background:${t.sectionBackgroundColor};color:${t.tableHeaderTextColor};'
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'border:1px solid #ccc;padding:6px 12px;font-size:20px}'
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'.slide td{color:${t.tableTextColor};border:1px solid #ccc;padding:6px 12px;font-size:20px}'
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'@media print{body{background:#fff}.slide{margin:0;box-shadow:none;'
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'border-radius:0;page-break-after:always;width:100%;min-height:100vh}}';
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}
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String _cssFontStack(String font) {
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if (font == 'EB Garamond') return "'EB Garamond', Georgia, serif";
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const serif = {'Georgia', 'Times New Roman'};
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final generic = serif.contains(font) ? 'serif' : 'sans-serif';
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return "'$font', $generic";
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}
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/// Embed the bundled EB Garamond variable font as base64 so it works offline.
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/// Returns an empty string for any other (system) font.
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Future<String> _ebGaramondFontFace(String font) async {
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if (font != 'EB Garamond') return '';
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try {
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final bytes = await loadBytes('assets/fonts/EBGaramond-Variable.ttf');
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final b64 = base64Encode(bytes);
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return "@font-face{font-family:'EB Garamond';font-weight:400 800;"
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"font-style:normal;src:url(data:font/ttf;base64,$b64) "
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"format('truetype');}";
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} catch (_) {
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return ''; // Fall back to the CSS font stack if the asset is missing.
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}
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}
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static const _mathjaxConfig =
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r'''window.MathJax={tex:{inlineMath:[['$','$']],displayMath:[['$$','$$']]},svg:{fontCache:'global'},startup:{typeset:false}};''';
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static const _baseCss = r'''
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*{box-sizing:border-box}
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html,body{margin:0;padding:0}
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body{background:#1e1e1e;font-family:-apple-system,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;color:#1a1a1a}
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.slide{position:relative;width:1280px;min-height:720px;margin:24px auto;background:#fff;padding:60px;overflow:hidden;box-shadow:0 4px 24px rgba(0,0,0,.4);border-radius:4px}
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.slide h1{font-size:48px;margin:.15em 0}
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.slide h2{font-size:34px;margin:.15em 0}
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.slide p,.slide li{font-size:24px;line-height:1.45}
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.slide pre{background:#f6f8fa;border:1px solid #e1e4e8;border-radius:6px;padding:16px;overflow:auto;font-size:18px}
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.slide code{font-family:SFMono-Regular,Consolas,"Liberation Mono",monospace}
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.slide pre.mermaid{background:transparent;border:0;text-align:center}
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.slide img{max-width:100%}
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.slide blockquote{border-left:4px solid #ccc;margin:.5em 0;padding-left:16px;color:#555}
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.slide table{border-collapse:collapse}.slide th,.slide td{border:1px solid #ccc;padding:6px 12px;font-size:20px}
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@media print{body{background:#fff}.slide{margin:0;box-shadow:none;border-radius:0;page-break-after:always;width:100%;min-height:100vh}}
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''';
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static const _renderScript = r'''
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(function(){
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if(window.marked&&marked.setOptions){marked.setOptions({gfm:true,breaks:false});}
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document.querySelectorAll('section.slide').forEach(function(sec){
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var holder=sec.querySelector('script[type="text/markdown"]');
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var src=holder?holder.textContent:'';
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var div=document.createElement('div');div.className='content';
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div.innerHTML=window.marked?marked.parse(src):src;
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sec.innerHTML='';sec.appendChild(div);
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});
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document.querySelectorAll('code.language-mermaid').forEach(function(code){
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var pre=code.closest('pre');if(!pre)return;
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var holder=document.createElement('pre');holder.className='mermaid';
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holder.textContent=code.textContent;pre.replaceWith(holder);
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});
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if(window.hljs){document.querySelectorAll('pre code').forEach(function(el){try{hljs.highlightElement(el);}catch(e){}});}
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if(window.mermaid){try{mermaid.initialize({startOnLoad:false});mermaid.run();}catch(e){}}
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if(window.MathJax&&MathJax.typesetPromise){MathJax.typesetPromise();}
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})();
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''';
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}
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