import { readFile } from "node:fs/promises";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";
import type { Integration, IntegrationContext } from "muddle/contracts";
import { renderMarkdown } from "muddle/markdown";
import katex from "katex";

export function renderLatex(source: string, displayMode = false): string {
	return katex.renderToString(source, { displayMode, throwOnError: false, trust: false });
}

export function renderMathMarkdown(source: string): string {
	const formulas: string[] = [];
	const body = source.replace(/\$\$([\s\S]+?)\$\$|(?<!\\)\$([^$\n]+?)\$/g, (_match, display, inline) => {
		formulas.push(renderLatex(display ?? inline, display !== undefined));
		return `MUDDLEMATH${formulas.length - 1}END`;
	});
	return renderMarkdown(body).replace(/MUDDLEMATH(\d+)END/g, (_match, index) => formulas[Number(index)] ?? "");
}

export interface LatexIntegrationOptions { route?: string }

export function latexIntegration(options: LatexIntegrationOptions = {}): Integration {
	const route = options.route ?? "/_muddle/katex.css";
	return {
		name: "latex",
		async setup(context: IntegrationContext) {
			const base = dirname(fileURLToPath(import.meta.resolve("katex/package.json")));
			const css = await readFile(join(base, "dist", "katex.min.css"), "utf8");
			context.loader("latex-markdown", {
				name: "latex-markdown",
				extensions: [".latex.md", ".latex.markdown"],
				load(file) { return { data: {}, content: renderMathMarkdown(file.source) }; },
			});
			context.route("GET", route, () => new Response(css, { headers: { "content-type": "text/css; charset=utf-8", "cache-control": "public, max-age=31536000, immutable" } }));
		},
	};
}