import React from 'react';
import katex from 'katex';
import 'katex/dist/katex.min.css';

type KaTeXProps = {
  /** Raw LaTeX source (without `$`/`$$` delimiters). */
  latex: string;
  /** Render as block (display) math when true, inline otherwise. */
  displayMode?: boolean;
};

/**
 * Lazily-loaded KaTeX renderer.
 *
 * This module statically imports `katex` and its stylesheet, so both only enter
 * the bundle via the dynamic `import()` of this file (see the `lazy()` wrapper
 * in `react-custom-html-parser.tsx`). They are therefore NOT part of the eager
 * import graph.
 *
 * We render with `throwOnError: false`, so KaTeX itself renders a parse error
 * inline (in its error colour) rather than throwing. The HTML returned by
 * `renderToString` is produced by our own trusted call from a fixed options
 * object — it is safe to inject via `dangerouslySetInnerHTML`.
 *
 * `maxSize`/`maxExpand` cap how large a single glyph (`\\rule`, etc.) or macro
 * expansion remote LaTeX can request, and `trust: false` disables commands
 * that can embed arbitrary HTML/URLs (e.g. `\\includegraphics`, `\\href`) —
 * without these a hostile `$$...$$` from a remote message can DoS or (via
 * `trust`) inject unsafe links (Gitea #65). `strict: 'ignore'` keeps unknown-
 * but-harmless LaTeX from spamming the console as before. Extremely long
 * source is rendered as plain text rather than handed to KaTeX at all.
 */
const MAX_LATEX_LENGTH = 5000;

export default function KaTeX({ latex, displayMode = false }: KaTeXProps) {
  if (latex.length > MAX_LATEX_LENGTH) {
    const Plain = displayMode ? 'div' : 'span';
    return <Plain>{latex}</Plain>;
  }

  const html = katex.renderToString(latex, {
    displayMode,
    throwOnError: false,
    output: 'htmlAndMathml',
    maxSize: 10,
    maxExpand: 100,
    trust: false,
    strict: 'ignore',
  });

  const Wrapper = displayMode ? 'div' : 'span';

  return (
    <Wrapper
      // KaTeX output is generated by our own render call (trusted-safe).

      dangerouslySetInnerHTML={{ __html: html }}
    />
  );
}