/**
 * Local React-Email preview server.
 *
 * Run via `pnpm --filter @toolctrl/mail preview` and visit
 * http://localhost:3001 — the index lists every transactional
 * template; clicking a name renders the template with the sample
 * props from `previews.ts` so designers can iterate without
 * triggering live email sends.
 *
 * Intentionally tiny — uses Node's built-in `http` server so the
 * mail package keeps a small dep footprint. For production-grade
 * preview workflows (visual-regression diffing, screenshot capture)
 * mount the React-Email components in Storybook (Phase 08).
 */
import { createServer, type IncomingMessage, type ServerResponse } from "node:http";
import { reactTransactionalTemplateNames, renderTransactionalEmail } from "../src/templates-react/render.js";
import { samplePropsByTemplate } from "./previews.js";

const PORT = Number.parseInt(process.env.MAIL_PREVIEW_PORT ?? "3001", 10);

function escapeHtml(value: string): string {
  return value
    .replaceAll("&", "&")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
    .replaceAll('"', "&quot;");
}

function renderIndex(): string {
  const names = reactTransactionalTemplateNames();
  const items = names
    .map((name) => `<li><a href="/preview/${name}">${escapeHtml(name)}</a> &middot; <a href="/preview/${name}?format=text">text</a></li>`)
    .join("");
  return `<!doctype html><html><head><meta charset="utf-8"><title>Mail Preview</title>
<style>body{font-family:system-ui;margin:40px;max-width:720px}a{color:#2563eb}li{margin:6px 0}</style>
</head><body><h1>Mail template preview</h1>
<p>Browsing ${names.length} transactional templates. Each entry links to the rendered HTML and a plain-text fallback.</p>
<ul>${items}</ul>
</body></html>`;
}

function handle(req: IncomingMessage, res: ServerResponse): void {
  const url = new URL(req.url ?? "/", `http://localhost:${PORT}`);
  if (url.pathname === "/" || url.pathname === "/preview") {
    res.writeHead(200, { "content-type": "text/html; charset=utf-8" });
    res.end(renderIndex());
    return;
  }
  const match = /^\/preview\/(.+)$/.exec(url.pathname);
  if (!match) {
    res.writeHead(404, { "content-type": "text/plain" });
    res.end("not found");
    return;
  }
  const templateName = match[1] as ReturnType<typeof reactTransactionalTemplateNames>[number];
  const sample = samplePropsByTemplate[templateName];
  if (!sample) {
    res.writeHead(404, { "content-type": "text/plain" });
    res.end(`unknown template: ${templateName}`);
    return;
  }
  try {
    const rendered = renderTransactionalEmail(templateName, sample);
    if (url.searchParams.get("format") === "text") {
      res.writeHead(200, { "content-type": "text/plain; charset=utf-8" });
      res.end(rendered.text);
      return;
    }
    res.writeHead(200, { "content-type": "text/html; charset=utf-8" });
    res.end(rendered.html);
  } catch (error) {
    res.writeHead(500, { "content-type": "text/plain" });
    res.end(`render failed: ${(error as Error).message}`);
  }
}

const server = createServer(handle);
server.listen(PORT, () => {
  // eslint-disable-next-line no-console
  console.log(`📧 Mail preview server listening on http://localhost:${PORT}`);
});