build_webstatic/src/MarkdownProcessor.cs

using Markdig;
using System.Text.RegularExpressions;

namespace GCBoK.WebStaticBuilder;

/// <summary>Markdown processing with Markdig and post-processing.</summary>
public static class MarkdownProcessor
{
    private static readonly Lazy<MarkdownPipeline> Pipeline = new(() =>
        new MarkdownPipelineBuilder().UseAdvancedExtensions().Build());

    public static string RenderMarkdown(string content)
    {
        var pipeline = Pipeline.Value;
        return Markdown.ToHtml(content, pipeline);
    }

    public static string MermaidPostprocess(string html)
    {
        var pattern1 = @"<pre><code class=""language-mermaid"">(.*?)</code></pre>";
        var regex1 = new Regex(pattern1, RegexOptions.Singleline);
        html = regex1.Replace(html, m =>
        {
            var code = m.Groups[1].Value
                .Replace("&lt;", "<").Replace("&gt;", ">").Replace("&amp;", "&");
            return $"<div class=\"mermaid\">{code}</div>";
        });

        var pattern2 = @"<pre class=""mermaid"">(.*?)</pre>";
        var regex2 = new Regex(pattern2, RegexOptions.Singleline);
        html = regex2.Replace(html, m =>
        {
            var code = m.Groups[1].Value
                .Replace("&lt;", "<").Replace("&gt;", ">").Replace("&amp;", "&");
            return $"<div class=\"mermaid\">{code}</div>";
        });

        return html;
    }

    public static string TablePostprocess(string html)
    {
        return html.Replace("<table>", "<table class=\"gc-table\">");
    }
}