serve.mjs

/**
 * serve.mjs — a local static server for dist/, for previewing a build.
 *
 * It resolves clean URLs the way Netlify does (`/spec/` → `/spec/index.html`) and
 * falls back to `404.html`, so what you see locally is what gets published.
 *
 * `serve()` is exported because test-layout.mjs drives a real browser against
 * this same server: one definition of how a path resolves, rather than two that
 * can drift apart.
 */

import { createReadStream } from "node:fs";
import { stat } from "node:fs/promises";
import { createServer } from "node:http";
import { extname, join, normalize, resolve as resolvePath } from "node:path";
import { fileURLToPath } from "node:url";

const ROOT = "dist";

const TYPES = {
  ".html": "text/html; charset=utf-8",
  ".css": "text/css; charset=utf-8",
  ".js": "text/javascript; charset=utf-8",
  ".mjs": "text/javascript; charset=utf-8",
  ".json": "application/json; charset=utf-8",
  ".svg": "image/svg+xml",
  ".png": "image/png",
  ".xml": "application/xml; charset=utf-8",
  ".txt": "text/plain; charset=utf-8",
};

/** The schema is served as schema+json, which is what a $ref consumer expects. */
function contentType(path) {
  if (path.endsWith("-schema.json")) return "application/schema+json; charset=utf-8";
  return TYPES[extname(path)] ?? "application/octet-stream";
}

async function resolveFile(urlPath) {
  const clean = normalize(decodeURIComponent(urlPath.split("?")[0])).replace(/^(\.\.[/\\])+/, "");
  const candidates = clean.endsWith("/")
    ? [join(ROOT, clean, "index.html")]
    : [join(ROOT, clean), join(ROOT, clean, "index.html"), join(ROOT, `${clean}.html`)];

  for (const candidate of candidates) {
    try {
      const info = await stat(candidate);
      if (info.isFile()) return candidate;
    } catch {}
  }
  return null;
}

/** Start the server. Port 0 asks the OS for a free one, which is what tests want. */
export function serve(port = Number(process.env.PORT ?? 4173)) {
  const server = createServer(async (req, res) => {
    const file = (await resolveFile(req.url)) ?? join(ROOT, "404.html");
    const status = file.endsWith("404.html") && !req.url.includes("404") ? 404 : 200;
    res.writeHead(status, { "content-type": contentType(file), "cache-control": "no-store" });
    createReadStream(file).pipe(res);
  });
  return new Promise((ready) => server.listen(port, () => ready(server)));
}

// Only when run as a script, so importing it for a test does not start a server.
if (process.argv[1] && resolvePath(process.argv[1]) === fileURLToPath(import.meta.url)) {
  const server = await serve();
  console.log(`openpredicate.tech → http://localhost:${server.address().port}`);
}