import { existsSync, readFileSync } from "node:fs";
import { join, resolve } from "node:path";
import { gzipSync } from "node:zlib";
import type { ServerResponse, IncomingMessage } from "node:http";
import { isPathInsideRoot } from "../utils/paths.ts";

const MIME: Record<string, string> = {
	".html": "text/html; charset=utf-8",
	".js": "application/javascript; charset=utf-8",
	".css": "text/css; charset=utf-8",
	".png": "image/png",
	".svg": "image/svg+xml",
	".woff2": "font/woff2",
	".woff": "font/woff",
	".ico": "image/x-icon",
	".webmanifest": "application/manifest+json",
	".json": "application/json",
};

const GZIPABLE = new Set([".html", ".js", ".css", ".json", ".webmanifest"]);

// Vite build outputs hashed filenames like index-DeT2iZAf.js
const HASHED_FILE_RE = /-[A-Za-z0-9_-]{6,}\.\w+$/;

function getCacheControl(file: string): string | undefined {
	if (file === "/index.html") {
		return "no-cache";
	}
	if (HASHED_FILE_RE.test(file) || file.endsWith(".woff2") || file.endsWith(".woff")) {
		return "public, max-age=31536000, immutable";
	}
	return undefined;
}

export function serveStatic(
	publicDir: string,
	urlPath: string,
	req: IncomingMessage,
	res: ServerResponse,
	spaFallback = false,
): void {
	const file = urlPath === "/" ? "/index.html" : urlPath;
	const full = join(publicDir, file);
	const resolvedPublic = resolve(publicDir);
	const resolvedFull = resolve(full);
	if (!isPathInsideRoot(resolvedPublic, resolvedFull) && resolvedFull !== resolvedPublic) {
		res.writeHead(403);
		res.end("Forbidden");
		return;
	}
	if (!existsSync(full)) {
		if (spaFallback && !urlPath.includes(".")) {
			serveStatic(publicDir, "/index.html", req, res, false);
			return;
		}
		res.writeHead(404);
		res.end("Not found");
		return;
	}
	const ext = file.match(/\.\w+$/)?.[0] || ".html";
	const mimeType = MIME[ext] || "application/octet-stream";
	const content = readFileSync(full);

	const headers: Record<string, string> = {
		"Content-Type": mimeType,
	};

	const cacheControl = getCacheControl(file);
	if (cacheControl) {
		headers["Cache-Control"] = cacheControl;
	}

	const acceptEncoding = req.headers["accept-encoding"] || "";
	const shouldGzip = GZIPABLE.has(ext) && acceptEncoding.includes("gzip");

	if (shouldGzip) {
		const compressed = gzipSync(content);
		headers["Content-Encoding"] = "gzip";
		res.writeHead(200, headers);
		res.end(compressed);
		return;
	}

	res.writeHead(200, headers);
	res.end(content);
}