using Ganss.Xss;
using Markdig;
using Markdig.Syntax;

namespace XFESystem.Documents;

/// <summary>The website's MarkdownService pipeline, independent of ASP.NET and host file access.</summary>
public sealed class MarkdownRenderer
{
    private readonly MarkdownPipeline _pipeline = new MarkdownPipelineBuilder()
        .UseAdvancedExtensions()
        .UseAutoIdentifiers()
        .Build();

    public string RenderHtml(string? markdown)
    {
        if (string.IsNullOrEmpty(markdown)) return string.Empty;
        // A sanitizer per call avoids sharing its mutable parser across concurrent document previews.
        var sanitizer = new HtmlSanitizer();
        sanitizer.AllowedTags.Remove("button");
        sanitizer.AllowedTags.Remove("script");
        sanitizer.AllowedTags.Remove("css");
        sanitizer.AllowedAttributes.Add("id");
        sanitizer.AllowedAttributes.Add("class");
        sanitizer.AllowedAttributes.Remove("script");
        return sanitizer.Sanitize(Markdown.ToHtml(markdown, _pipeline));
    }

    public MarkdownDocument Parse(string? markdown) => Markdown.Parse(markdown ?? string.Empty, _pipeline);
}