import { readdir, readFile } from "node:fs/promises";
import { dirname, extname, join } from "node:path";
import { fileURLToPath } from "node:url";
import { compile } from "tailwindcss";
import type { Integration, IntegrationContext } from "muddle/contracts";

export interface TailwindOptions {
	route?: string;
	css?: string;
	content?: string[];
}

const SCANNED_EXTENSIONS = new Set([".ts", ".tsx", ".js", ".jsx", ".html", ".spug", ".mdx"]);

export async function tailwindCandidates(root: string, paths?: string[]): Promise<string[]> {
	const candidates = new Set<string>();
	const visit = async (dir: string): Promise<void> => {
		for (const entry of await readdir(dir, { withFileTypes: true })) {
			if (entry.name === "node_modules" || entry.name === "dist" || entry.name.startsWith(".")) continue;
			const path = join(dir, entry.name);
			if (entry.isDirectory()) { await visit(path); continue; }
			if (!SCANNED_EXTENSIONS.has(extname(entry.name))) continue;
			if (paths && !paths.some((value) => path.includes(value))) continue;
			const source = await readFile(path, "utf8");
			for (const match of source.matchAll(/(?:class|className)\s*=\s*["'`]([^"'`]+)["'`]/g)) {
				for (const value of (match[1] ?? "").split(/\s+/)) if (value) candidates.add(value);
			}
		}
	};
	await visit(root);
	return [...candidates];
}

export async function compileTailwind(css: string, candidates: string[] = []): Promise<string> {
	const tailwindCss = join(dirname(fileURLToPath(import.meta.resolve("tailwindcss/package.json"))), "index.css");
	const compiler = await compile(css, {
		base: process.cwd(),
		loadStylesheet: async (id) => {
			if (!["tailwindcss", "tailwindcss/theme.css", "tailwindcss/utilities.css"].includes(id)) throw new Error(`Unsupported Tailwind stylesheet "${id}"`);
			const path = id === "tailwindcss" ? tailwindCss : join(dirname(tailwindCss), id.split("/")[1]!);
			return { path, base: process.cwd(), content: await readFile(path, "utf8") };
		},
	});
	return compiler.build(candidates);
}

export function tailwindIntegration(options: TailwindOptions = {}): Integration {
	const route = options.route ?? "/_muddle/tailwind.css";
	const source = options.css ?? '@import "tailwindcss";';
	return {
		name: "tailwind",
		async setup(context: IntegrationContext) {
			const build = () => tailwindCandidates(context.config.root, options.content).then((candidates) => compileTailwind(source, candidates));
			context.loader("tailwind", {
				name: "tailwind",
				extensions: [".tailwind.css"],
				async load(file) { return { data: {}, content: await compileTailwind(file.source, await tailwindCandidates(context.config.root, options.content)) }; },
			});
			context.route("GET", route, async () => new Response(await build(), { headers: { "content-type": "text/css; charset=utf-8", "cache-control": "public, max-age=60" } }));
		},
	};
}