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",
						},
					}),
			);
		},
	};
}