// Undercooked — client shell entry point (phase 01).
//
// There is no game logic here on purpose. Phase 05 shipped the server-side
// room shell (supervisor, room FSM, session store); phase 06 adds the WebSocket
// transport and phase 07 replaces the placeholder button handlers with the lobby
// flow and adds render/ (Canvas 2D). What this file owns today:
//   * the anonymous per-tab session token (PLAN.md A16),
//   * the last room code typed in this tab, so a reload can rejoin fast,
//   * mounting the lobby screen and announcing state into #status.
// It is a plain ES module served from /static/ — no bundler, no framework, no
// remote import (PLAN.md A10/A12).

const TOKEN_KEY = "uc.token";
const LAST_CODE_KEY = "uc.lastCode";
const CODE_LENGTH = 5;
const NOT_IMPLEMENTED = "Not implemented until phase 07.";
const READY_MESSAGE = "Pick a kitchen to start.";

/** Base64url without padding, so the token is safe in a query string or header. */
function base64url(bytes) {
  let binary = "";
  for (const byte of bytes) binary += String.fromCharCode(byte);
  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

/** A random, unguessable id for this browser tab (identity, not an account). */
export function randomToken() {
  const bytes = new Uint8Array(24);
  globalThis.crypto.getRandomValues(bytes);
  return base64url(bytes);
}

function read(storage, key) {
  try {
    return storage.getItem(key);
  } catch {
    return null; // private browsing / storage disabled: stay functional for this tab only
  }
}

function write(storage, key, value) {
  try {
    storage.setItem(key, value);
  } catch {
    /* nothing to persist to; the in-memory value still works */
  }
}

/** The tab's session token, created once per tab and kept in sessionStorage. */
export function getToken(storage = globalThis.sessionStorage) {
  const existing = read(storage, TOKEN_KEY);
  if (typeof existing === "string" && existing.length > 0) return existing;
  const token = randomToken();
  write(storage, TOKEN_KEY, token);
  return token;
}

/** Uppercase what the user typed and keep only characters a code can contain. */
export function normalizeCode(value) {
  return String(value ?? "")
    .toUpperCase()
    .replace(/[^0-9A-Z]/g, "")
    .slice(0, CODE_LENGTH);
}

export function lastCode(storage = globalThis.sessionStorage) {
  return read(storage, LAST_CODE_KEY) || "";
}

export function rememberCode(code, storage = globalThis.sessionStorage) {
  write(storage, LAST_CODE_KEY, normalizeCode(code));
}

/** Write the live region. `kind` is "info" | "error" and only changes styling. */
export function announce(message, root = document, kind = "info") {
  const region = root.getElementById("status");
  if (!region) return;
  region.textContent = message;
  region.dataset.kind = kind;
}

/**
 * Wire the lobby screen. Returns the tab identity so later phases can reuse it.
 */
export function mount(root = document) {
  const token = getToken();
  const createButton = root.getElementById("create-lobby");
  const joinForm = root.getElementById("join-form");
  const joinInput = root.getElementById("join-code");

  const remembered = lastCode();
  if (joinInput && remembered) joinInput.value = remembered;

  if (createButton) {
    createButton.addEventListener("click", () => {
      // Phase 07 (on the phase-06 transport): POST to the room supervisor,
      // open /ws/{code}.
      announce(NOT_IMPLEMENTED, root);
    });
  }

  if (joinForm) {
    joinForm.addEventListener("submit", (event) => {
      event.preventDefault();
      const code = normalizeCode(joinInput ? joinInput.value : "");
      if (joinInput) joinInput.value = code;
      if (code.length !== CODE_LENGTH) {
        announce(`A room code is ${CODE_LENGTH} characters.`, root, "error");
        if (joinInput) joinInput.focus();
        return;
      }
      rememberCode(code);
      // Phase 07 (on the phase-06 transport): join the room over the
      // WebSocket.
      announce(NOT_IMPLEMENTED, root);
    });
  }

  if (!lastCode() && root.getElementById("status")) {
    announce(READY_MESSAGE, root);
  }

  return { token, code: lastCode() };
}

// Auto-mount when loaded as the page's module, but stay importable (and
// therefore testable) without a lobby in the document.
if (typeof document !== "undefined" && document.getElementById("screen-lobby")) {
  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", () => mount(), { once: true });
  } else {
    mount();
  }
}