/**
 * The island bootstrap served at `/__wrnexus/islands.js`.
 *
 * Mirrors the `@wrnexus/csr` pattern: this file is only ever fetched when a
 * `data-wrn-island` marker is present, so island-free pages download nothing —
 * including React.
 */
export function getIslandRuntime(development = false): string {
  return `
(function () {
  function loader(name) {
    return import("/__wrnexus/island/" + encodeURIComponent(name) + ".js");
  }

  function boot() {
    if (!document.querySelector("[data-wrn-island]")) return;
    import("/__wrnexus/island/runtime.js").then(function (runtime) {
      runtime.mountIslands(document, { loader: loader, development: ${development} });
      window.__wrnexusUnmountIslands = function (root) {
        runtime.unmountIslands(root || document);
      };
      window.__wrnexusRemountIslands = function (root) {
        return runtime.remountIslands(root || document, {
          loader: loader,
          development: ${development}
        });
      };
      // HMR morphs the server placeholder back over the mounted island, which
      // discards the React tree. Remount once the DOM has settled.
      window.addEventListener("wrnexus:hmr-updated", function () {
        window.__wrnexusRemountIslands();
      });
    }).catch(function (error) {
      console.error("[wrnexus] failed to load the island runtime", error);
    });
  }

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", boot);
  } else {
    boot();
  }
})();
`;
}