import { readFile, writeFile } from "node:fs/promises";
import { join } from "node:path";
import { defineConfig, type Plugin } from "vite";

/**
 * The office's copy of the page, emitted from the city's.
 *
 * `office.lumbridgecorp.com` and `tera.lumbridgecorp.com` are one bundle behind
 * two names, and the app works out which door it is at runtime by reading its
 * own hostname. A crawler cannot: it reads the HTML and nothing else. So a
 * single `index.html` means both doors unfurl with the same title, the same
 * sentence and the same picture — and the office door's whole reason to exist is
 * that it is a different place.
 *
 * The obvious fix, a second hand-written `office.html`, is the one the Caddy
 * config already argues against for the static root: "sharing the root rather
 * than copying it means a deploy cannot leave the two doors on different
 * builds". Two 900-line files each carrying the whole inline stylesheet would
 * drift on the first CSS change, and nothing would notice, because the drift is
 * invisible until somebody opens the other door.
 *
 * So there is one source and the build emits both shells. Everything outside the
 * `ogc:` markers in `index.html` is copied byte for byte — the stylesheet, the
 * DOM, the script tag Vite has already rewritten to the hashed bundle — and only
 * the block between them is replaced. A change to the interface reaches both
 * doors by construction, and the only thing that can differ is the thing that is
 * supposed to.
 *
 * It runs in `writeBundle` rather than `transformIndexHtml` because it needs the
 * *finished* document, after Vite has substituted the asset URLs. Transforming
 * earlier would emit a page pointing at unhashed source paths.
 */
function twoDoors(): Plugin {
  const MARKER_END = "<!-- ogc:end -->";

  const OFFICE = `
    <title>Spaces — an office you can walk around</title>
    <meta
      name="description"
      content="Lumbridge HQ, one floor: the rooms, the desks and who is at them. Rendered in the browser from a data file anybody can copy. Apache-2.0, self-hostable."
    />
    <link rel="canonical" href="https://office.lumbridgecorp.com/" />

    <meta property="og:type" content="website" />
    <meta property="og:site_name" content="Lumbridge Spaces" />
    <meta property="og:title" content="Spaces — an office you can walk around" />
    <meta
      property="og:description"
      content="The rooms, the desks and who is at them — one floor plan, rendered from a data file anybody can copy."
    />
    <meta property="og:url" content="https://office.lumbridgecorp.com/" />
    <meta property="og:image" content="https://office.lumbridgecorp.com/og-office.png" />
    <meta property="og:image:type" content="image/png" />
    <meta property="og:image:width" content="1200" />
    <meta property="og:image:height" content="630" />
    <meta
      property="og:image:alt"
      content="Lumbridge HQ seen from above as a cutaway model, desks and meeting rooms visible, people at their seats."
    />

    <meta name="twitter:card" content="summary_large_image" />
    <meta name="twitter:title" content="Spaces — an office you can walk around" />
    <meta
      name="twitter:description"
      content="The rooms, the desks and who is at them — one floor plan, rendered from a data file anybody can copy."
    />
    <meta name="twitter:image" content="https://office.lumbridgecorp.com/og-office.png" />`;

  return {
    name: "lumbridge:two-doors",
    apply: "build",
    async writeBundle(options) {
      const dir = options.dir ?? "dist";
      const html = await readFile(join(dir, "index.html"), "utf8");

      const open = html.indexOf("ogc:start");
      const end = html.indexOf(MARKER_END);
      // Loudly, rather than by silently shipping two identical shells. A card
      // that is quietly the wrong one is the failure this plugin exists to
      // prevent, so losing the markers must not be a no-op.
      if (open === -1 || end === -1) {
        this.error("index.html has no ogc:start/ogc:end markers — cannot emit office.html");
        return;
      }
      // The opening marker sits inside a larger comment, so cut from the start
      // of that comment: otherwise the explanation ships on both doors while
      // being true of only one.
      const from = html.lastIndexOf("<!--", open);
      const office =
        html.slice(0, from) +
        "<!-- The office door. Generated from index.html by `twoDoors` in vite.config.ts. -->" +
        OFFICE +
        html.slice(end + MARKER_END.length);

      await writeFile(join(dir, "office.html"), office, "utf8");
    },
  };
}

export default defineConfig({
  // Mounted under tera.lumbridgecorp.com in production; the trailing
  // slash matters, since every asset URL is resolved against it.
  base: process.env.TERA_BASE ?? "/",
  plugins: [twoDoors()],
  build: {
    outDir: "dist",
    target: "es2022",
    // Two entries. `login.html` used to sit in `public/`, which Vite copies
    // verbatim — so `import.meta.env` was never substituted there and the page
    // could not be told which identity provider to sign in against. It is a real
    // entry now; the built URL (`/login.html`) is unchanged.
    //
    // `office.html` is deliberately not a third entry: it is the same document
    // as `index.html` with a different head, so making it one would give it its
    // own copy of the bundle graph. It is emitted after the build instead.
    rollupOptions: { input: { index: "index.html", login: "login.html" } },
  },
});