import { createReadStream, statSync } from "node:fs";
import { createServer } from "node:http";
import { dirname, extname, resolve, sep } from "node:path";
import { fileURLToPath } from "node:url";

const packageRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
const defaultEditorDirectory = resolve(packageRoot, "editor");

const contentTypes = new Map([
  [".css", "text/css; charset=utf-8"],
  [".html", "text/html; charset=utf-8"],
  [".js", "text/javascript; charset=utf-8"],
  [".json", "application/json; charset=utf-8"],
  [".svg", "image/svg+xml"],
  [".wasm", "application/wasm"],
]);

function respond(response, statusCode, message) {
  response.writeHead(statusCode, {
    "Content-Type": "text/plain; charset=utf-8",
    "Cache-Control": "no-store",
    "X-Content-Type-Options": "nosniff",
  });
  response.end(message);
}

export function createEditorServer({ editorDirectory = defaultEditorDirectory } = {}) {
  const root = resolve(editorDirectory);
  const rootPrefix = `${root}${sep}`;

  return createServer((request, response) => {
    if (request.method !== "GET" && request.method !== "HEAD") {
      respond(response, 405, "Method Not Allowed");
      return;
    }

    let pathname;
    try {
      pathname = decodeURIComponent(new URL(request.url ?? "/", "http://localhost").pathname);
    } catch {
      respond(response, 400, "Bad Request");
      return;
    }

    if (pathname.endsWith("/")) pathname += "index.html";
    const filePath = resolve(root, `.${pathname}`);
    if (filePath !== root && !filePath.startsWith(rootPrefix)) {
      respond(response, 403, "Forbidden");
      return;
    }

    let stats;
    try {
      stats = statSync(filePath);
    } catch {
      respond(response, 404, "Not Found");
      return;
    }

    if (!stats.isFile()) {
      respond(response, 404, "Not Found");
      return;
    }

    response.writeHead(200, {
      "Content-Type": contentTypes.get(extname(filePath).toLowerCase()) ?? "application/octet-stream",
      "Content-Length": stats.size,
      "Cache-Control": "no-store",
      "X-Content-Type-Options": "nosniff",
    });

    if (request.method === "HEAD") {
      response.end();
      return;
    }

    const stream = createReadStream(filePath);
    stream.on("error", () => response.destroy());
    stream.pipe(response);
  });
}

export function startEditorServer({ host = "127.0.0.1", port = 55173 } = {}) {
  const server = createEditorServer();

  return new Promise((resolvePromise, reject) => {
    const onError = (error) => reject(error);
    server.once("error", onError);
    server.listen(port, host, () => {
      server.off("error", onError);
      const address = server.address();
      const actualPort = typeof address === "object" && address ? address.port : port;
      resolvePromise({ server, url: `http://${host}:${actualPort}/` });
    });
  });
}